Imported Upstream version 60upstream/60

22 files changed, 3737 insertions, 0 deletions

diff --git a/src/pkg/crypto/openpgp/packet/Makefile b/src/pkg/crypto/openpgp/packet/Makefile
new file mode 100644
index 000000000..0f0d94eb1
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/Makefile
@@ -0,0 +1,22 @@
+# Copyright 2011 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+include ../../../../Make.inc
+
+TARG=crypto/openpgp/packet
+GOFILES=\
+	compressed.go\
+	encrypted_key.go\
+	literal.go\
+	one_pass_signature.go\
+	packet.go\
+	private_key.go\
+	public_key.go\
+	reader.go\
+	signature.go\
+	symmetrically_encrypted.go\
+	symmetric_key_encrypted.go\
+	userid.go\
+
+include ../../../../Make.pkg
diff --git a/src/pkg/crypto/openpgp/packet/compressed.go b/src/pkg/crypto/openpgp/packet/compressed.go
new file mode 100644
index 000000000..1c15c24c4
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/compressed.go
@@ -0,0 +1,39 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"compress/flate"
+	"compress/zlib"
+	"crypto/openpgp/error"
+	"io"
+	"os"
+	"strconv"
+)
+
+// Compressed represents a compressed OpenPGP packet. The decompressed contents
+// will contain more OpenPGP packets. See RFC 4880, section 5.6.
+type Compressed struct {
+	Body io.Reader
+}
+
+func (c *Compressed) parse(r io.Reader) os.Error {
+	var buf [1]byte
+	_, err := readFull(r, buf[:])
+	if err != nil {
+		return err
+	}
+
+	switch buf[0] {
+	case 1:
+		c.Body = flate.NewReader(r)
+	case 2:
+		c.Body, err = zlib.NewReader(r)
+	default:
+		err = error.UnsupportedError("unknown compression algorithm: " + strconv.Itoa(int(buf[0])))
+	}
+
+	return err
+}
diff --git a/src/pkg/crypto/openpgp/packet/compressed_test.go b/src/pkg/crypto/openpgp/packet/compressed_test.go
new file mode 100644
index 000000000..24fe501ed
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/compressed_test.go
@@ -0,0 +1,41 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"bytes"
+	"encoding/hex"
+	"os"
+	"io/ioutil"
+	"testing"
+)
+
+func TestCompressed(t *testing.T) {
+	packet, err := Read(readerFromHex(compressedHex))
+	if err != nil {
+		t.Errorf("failed to read Compressed: %s", err)
+		return
+	}
+
+	c, ok := packet.(*Compressed)
+	if !ok {
+		t.Error("didn't find Compressed packet")
+		return
+	}
+
+	contents, err := ioutil.ReadAll(c.Body)
+	if err != nil && err != os.EOF {
+		t.Error(err)
+		return
+	}
+
+	expected, _ := hex.DecodeString(compressedExpectedHex)
+	if !bytes.Equal(expected, contents) {
+		t.Errorf("got:%x want:%x", contents, expected)
+	}
+}
+
+const compressedHex = "a3013b2d90c4e02b72e25f727e5e496a5e49b11e1700"
+const compressedExpectedHex = "cb1062004d14c8fe636f6e74656e74732e0a"
diff --git a/src/pkg/crypto/openpgp/packet/encrypted_key.go b/src/pkg/crypto/openpgp/packet/encrypted_key.go
new file mode 100644
index 000000000..b4730cbc9
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/encrypted_key.go
@@ -0,0 +1,168 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"big"
+	"crypto/openpgp/elgamal"
+	"crypto/openpgp/error"
+	"crypto/rand"
+	"crypto/rsa"
+	"encoding/binary"
+	"io"
+	"os"
+	"strconv"
+)
+
+const encryptedKeyVersion = 3
+
+// EncryptedKey represents a public-key encrypted session key. See RFC 4880,
+// section 5.1.
+type EncryptedKey struct {
+	KeyId      uint64
+	Algo       PublicKeyAlgorithm
+	CipherFunc CipherFunction // only valid after a successful Decrypt
+	Key        []byte         // only valid after a successful Decrypt
+
+	encryptedMPI1, encryptedMPI2 []byte
+}
+
+func (e *EncryptedKey) parse(r io.Reader) (err os.Error) {
+	var buf [10]byte
+	_, err = readFull(r, buf[:])
+	if err != nil {
+		return
+	}
+	if buf[0] != encryptedKeyVersion {
+		return error.UnsupportedError("unknown EncryptedKey version " + strconv.Itoa(int(buf[0])))
+	}
+	e.KeyId = binary.BigEndian.Uint64(buf[1:9])
+	e.Algo = PublicKeyAlgorithm(buf[9])
+	switch e.Algo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
+		e.encryptedMPI1, _, err = readMPI(r)
+	case PubKeyAlgoElGamal:
+		e.encryptedMPI1, _, err = readMPI(r)
+		if err != nil {
+			return
+		}
+		e.encryptedMPI2, _, err = readMPI(r)
+	}
+	_, err = consumeAll(r)
+	return
+}
+
+func checksumKeyMaterial(key []byte) uint16 {
+	var checksum uint16
+	for _, v := range key {
+		checksum += uint16(v)
+	}
+	return checksum
+}
+
+// Decrypt decrypts an encrypted session key with the given private key. The
+// private key must have been decrypted first.
+func (e *EncryptedKey) Decrypt(priv *PrivateKey) os.Error {
+	var err os.Error
+	var b []byte
+
+	// TODO(agl): use session key decryption routines here to avoid
+	// padding oracle attacks.
+	switch priv.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
+		b, err = rsa.DecryptPKCS1v15(rand.Reader, priv.PrivateKey.(*rsa.PrivateKey), e.encryptedMPI1)
+	case PubKeyAlgoElGamal:
+		c1 := new(big.Int).SetBytes(e.encryptedMPI1)
+		c2 := new(big.Int).SetBytes(e.encryptedMPI2)
+		b, err = elgamal.Decrypt(priv.PrivateKey.(*elgamal.PrivateKey), c1, c2)
+	default:
+		err = error.InvalidArgumentError("cannot decrypted encrypted session key with private key of type " + strconv.Itoa(int(priv.PubKeyAlgo)))
+	}
+
+	if err != nil {
+		return err
+	}
+
+	e.CipherFunc = CipherFunction(b[0])
+	e.Key = b[1 : len(b)-2]
+	expectedChecksum := uint16(b[len(b)-2])<<8 | uint16(b[len(b)-1])
+	checksum := checksumKeyMaterial(e.Key)
+	if checksum != expectedChecksum {
+		return error.StructuralError("EncryptedKey checksum incorrect")
+	}
+
+	return nil
+}
+
+// SerializeEncryptedKey serializes an encrypted key packet to w that contains
+// key, encrypted to pub.
+func SerializeEncryptedKey(w io.Writer, rand io.Reader, pub *PublicKey, cipherFunc CipherFunction, key []byte) os.Error {
+	var buf [10]byte
+	buf[0] = encryptedKeyVersion
+	binary.BigEndian.PutUint64(buf[1:9], pub.KeyId)
+	buf[9] = byte(pub.PubKeyAlgo)
+
+	keyBlock := make([]byte, 1 /* cipher type */ +len(key)+2 /* checksum */ )
+	keyBlock[0] = byte(cipherFunc)
+	copy(keyBlock[1:], key)
+	checksum := checksumKeyMaterial(key)
+	keyBlock[1+len(key)] = byte(checksum >> 8)
+	keyBlock[1+len(key)+1] = byte(checksum)
+
+	switch pub.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
+		return serializeEncryptedKeyRSA(w, rand, buf, pub.PublicKey.(*rsa.PublicKey), keyBlock)
+	case PubKeyAlgoElGamal:
+		return serializeEncryptedKeyElGamal(w, rand, buf, pub.PublicKey.(*elgamal.PublicKey), keyBlock)
+	case PubKeyAlgoDSA, PubKeyAlgoRSASignOnly:
+		return error.InvalidArgumentError("cannot encrypt to public key of type " + strconv.Itoa(int(pub.PubKeyAlgo)))
+	}
+
+	return error.UnsupportedError("encrypting a key to public key of type " + strconv.Itoa(int(pub.PubKeyAlgo)))
+}
+
+func serializeEncryptedKeyRSA(w io.Writer, rand io.Reader, header [10]byte, pub *rsa.PublicKey, keyBlock []byte) os.Error {
+	cipherText, err := rsa.EncryptPKCS1v15(rand, pub, keyBlock)
+	if err != nil {
+		return error.InvalidArgumentError("RSA encryption failed: " + err.String())
+	}
+
+	packetLen := 10 /* header length */ + 2 /* mpi size */ + len(cipherText)
+
+	err = serializeHeader(w, packetTypeEncryptedKey, packetLen)
+	if err != nil {
+		return err
+	}
+	_, err = w.Write(header[:])
+	if err != nil {
+		return err
+	}
+	return writeMPI(w, 8*uint16(len(cipherText)), cipherText)
+}
+
+func serializeEncryptedKeyElGamal(w io.Writer, rand io.Reader, header [10]byte, pub *elgamal.PublicKey, keyBlock []byte) os.Error {
+	c1, c2, err := elgamal.Encrypt(rand, pub, keyBlock)
+	if err != nil {
+		return error.InvalidArgumentError("ElGamal encryption failed: " + err.String())
+	}
+
+	packetLen := 10 /* header length */
+	packetLen += 2 /* mpi size */ + (c1.BitLen()+7)/8
+	packetLen += 2 /* mpi size */ + (c2.BitLen()+7)/8
+
+	err = serializeHeader(w, packetTypeEncryptedKey, packetLen)
+	if err != nil {
+		return err
+	}
+	_, err = w.Write(header[:])
+	if err != nil {
+		return err
+	}
+	err = writeBig(w, c1)
+	if err != nil {
+		return err
+	}
+	return writeBig(w, c2)
+}
diff --git a/src/pkg/crypto/openpgp/packet/encrypted_key_test.go b/src/pkg/crypto/openpgp/packet/encrypted_key_test.go
new file mode 100644
index 000000000..b402245bd
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/encrypted_key_test.go
@@ -0,0 +1,126 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"big"
+	"bytes"
+	"crypto/rand"
+	"crypto/rsa"
+	"fmt"
+	"testing"
+)
+
+func bigFromBase10(s string) *big.Int {
+	b, ok := new(big.Int).SetString(s, 10)
+	if !ok {
+		panic("bigFromBase10 failed")
+	}
+	return b
+}
+
+var encryptedKeyPub = rsa.PublicKey{
+	E: 65537,
+	N: bigFromBase10("115804063926007623305902631768113868327816898845124614648849934718568541074358183759250136204762053879858102352159854352727097033322663029387610959884180306668628526686121021235757016368038585212410610742029286439607686208110250133174279811431933746643015923132833417396844716207301518956640020862630546868823"),
+}
+
+var encryptedKeyRSAPriv = &rsa.PrivateKey{
+	PublicKey: encryptedKeyPub,
+	D:         bigFromBase10("32355588668219869544751561565313228297765464314098552250409557267371233892496951383426602439009993875125222579159850054973310859166139474359774543943714622292329487391199285040721944491839695981199720170366763547754915493640685849961780092241140181198779299712578774460837139360803883139311171713302987058393"),
+}
+
+var encryptedKeyPriv = &PrivateKey{
+	PublicKey: PublicKey{
+		PubKeyAlgo: PubKeyAlgoRSA,
+	},
+	PrivateKey: encryptedKeyRSAPriv,
+}
+
+func TestDecryptingEncryptedKey(t *testing.T) {
+	const encryptedKeyHex = "c18c032a67d68660df41c70104005789d0de26b6a50c985a02a13131ca829c413a35d0e6fa8d6842599252162808ac7439c72151c8c6183e76923fe3299301414d0c25a2f06a2257db3839e7df0ec964773f6e4c4ac7ff3b48c444237166dd46ba8ff443a5410dc670cb486672fdbe7c9dfafb75b4fea83af3a204fe2a7dfa86bd20122b4f3d2646cbeecb8f7be8"
+	const expectedKeyHex = "d930363f7e0308c333b9618617ea728963d8df993665ae7be1092d4926fd864b"
+
+	p, err := Read(readerFromHex(encryptedKeyHex))
+	if err != nil {
+		t.Errorf("error from Read: %s", err)
+		return
+	}
+	ek, ok := p.(*EncryptedKey)
+	if !ok {
+		t.Errorf("didn't parse an EncryptedKey, got %#v", p)
+		return
+	}
+
+	if ek.KeyId != 0x2a67d68660df41c7 || ek.Algo != PubKeyAlgoRSA {
+		t.Errorf("unexpected EncryptedKey contents: %#v", ek)
+		return
+	}
+
+	err = ek.Decrypt(encryptedKeyPriv)
+	if err != nil {
+		t.Errorf("error from Decrypt: %s", err)
+		return
+	}
+
+	if ek.CipherFunc != CipherAES256 {
+		t.Errorf("unexpected EncryptedKey contents: %#v", ek)
+		return
+	}
+
+	keyHex := fmt.Sprintf("%x", ek.Key)
+	if keyHex != expectedKeyHex {
+		t.Errorf("bad key, got %s want %x", keyHex, expectedKeyHex)
+	}
+}
+
+func TestEncryptingEncryptedKey(t *testing.T) {
+	key := []byte{1, 2, 3, 4}
+	const expectedKeyHex = "01020304"
+	const keyId = 42
+
+	pub := &PublicKey{
+		PublicKey:  &encryptedKeyPub,
+		KeyId:      keyId,
+		PubKeyAlgo: PubKeyAlgoRSAEncryptOnly,
+	}
+
+	buf := new(bytes.Buffer)
+	err := SerializeEncryptedKey(buf, rand.Reader, pub, CipherAES128, key)
+	if err != nil {
+		t.Errorf("error writing encrypted key packet: %s", err)
+	}
+
+	p, err := Read(buf)
+	if err != nil {
+		t.Errorf("error from Read: %s", err)
+		return
+	}
+	ek, ok := p.(*EncryptedKey)
+	if !ok {
+		t.Errorf("didn't parse an EncryptedKey, got %#v", p)
+		return
+	}
+
+	if ek.KeyId != keyId || ek.Algo != PubKeyAlgoRSAEncryptOnly {
+		t.Errorf("unexpected EncryptedKey contents: %#v", ek)
+		return
+	}
+
+	err = ek.Decrypt(encryptedKeyPriv)
+	if err != nil {
+		t.Errorf("error from Decrypt: %s", err)
+		return
+	}
+
+	if ek.CipherFunc != CipherAES128 {
+		t.Errorf("unexpected EncryptedKey contents: %#v", ek)
+		return
+	}
+
+	keyHex := fmt.Sprintf("%x", ek.Key)
+	if keyHex != expectedKeyHex {
+		t.Errorf("bad key, got %s want %x", keyHex, expectedKeyHex)
+	}
+}
diff --git a/src/pkg/crypto/openpgp/packet/literal.go b/src/pkg/crypto/openpgp/packet/literal.go
new file mode 100644
index 000000000..9411572d7
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/literal.go
@@ -0,0 +1,90 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"encoding/binary"
+	"io"
+	"os"
+)
+
+// LiteralData represents an encrypted file. See RFC 4880, section 5.9.
+type LiteralData struct {
+	IsBinary bool
+	FileName string
+	Time     uint32 // Unix epoch time. Either creation time or modification time. 0 means undefined.
+	Body     io.Reader
+}
+
+// ForEyesOnly returns whether the contents of the LiteralData have been marked
+// as especially sensitive.
+func (l *LiteralData) ForEyesOnly() bool {
+	return l.FileName == "_CONSOLE"
+}
+
+func (l *LiteralData) parse(r io.Reader) (err os.Error) {
+	var buf [256]byte
+
+	_, err = readFull(r, buf[:2])
+	if err != nil {
+		return
+	}
+
+	l.IsBinary = buf[0] == 'b'
+	fileNameLen := int(buf[1])
+
+	_, err = readFull(r, buf[:fileNameLen])
+	if err != nil {
+		return
+	}
+
+	l.FileName = string(buf[:fileNameLen])
+
+	_, err = readFull(r, buf[:4])
+	if err != nil {
+		return
+	}
+
+	l.Time = binary.BigEndian.Uint32(buf[:4])
+	l.Body = r
+	return
+}
+
+// SerializeLiteral serializes a literal data packet to w and returns a
+// WriteCloser to which the data itself can be written and which MUST be closed
+// on completion. The fileName is truncated to 255 bytes.
+func SerializeLiteral(w io.WriteCloser, isBinary bool, fileName string, time uint32) (plaintext io.WriteCloser, err os.Error) {
+	var buf [4]byte
+	buf[0] = 't'
+	if isBinary {
+		buf[0] = 'b'
+	}
+	if len(fileName) > 255 {
+		fileName = fileName[:255]
+	}
+	buf[1] = byte(len(fileName))
+
+	inner, err := serializeStreamHeader(w, packetTypeLiteralData)
+	if err != nil {
+		return
+	}
+
+	_, err = inner.Write(buf[:2])
+	if err != nil {
+		return
+	}
+	_, err = inner.Write([]byte(fileName))
+	if err != nil {
+		return
+	}
+	binary.BigEndian.PutUint32(buf[:], time)
+	_, err = inner.Write(buf[:])
+	if err != nil {
+		return
+	}
+
+	plaintext = inner
+	return
+}
diff --git a/src/pkg/crypto/openpgp/packet/one_pass_signature.go b/src/pkg/crypto/openpgp/packet/one_pass_signature.go
new file mode 100644
index 000000000..ca826e4f4
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/one_pass_signature.go
@@ -0,0 +1,74 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"crypto"
+	"crypto/openpgp/error"
+	"crypto/openpgp/s2k"
+	"encoding/binary"
+	"io"
+	"os"
+	"strconv"
+)
+
+// OnePassSignature represents a one-pass signature packet. See RFC 4880,
+// section 5.4.
+type OnePassSignature struct {
+	SigType    SignatureType
+	Hash       crypto.Hash
+	PubKeyAlgo PublicKeyAlgorithm
+	KeyId      uint64
+	IsLast     bool
+}
+
+const onePassSignatureVersion = 3
+
+func (ops *OnePassSignature) parse(r io.Reader) (err os.Error) {
+	var buf [13]byte
+
+	_, err = readFull(r, buf[:])
+	if err != nil {
+		return
+	}
+	if buf[0] != onePassSignatureVersion {
+		err = error.UnsupportedError("one-pass-signature packet version " + strconv.Itoa(int(buf[0])))
+	}
+
+	var ok bool
+	ops.Hash, ok = s2k.HashIdToHash(buf[2])
+	if !ok {
+		return error.UnsupportedError("hash function: " + strconv.Itoa(int(buf[2])))
+	}
+
+	ops.SigType = SignatureType(buf[1])
+	ops.PubKeyAlgo = PublicKeyAlgorithm(buf[3])
+	ops.KeyId = binary.BigEndian.Uint64(buf[4:12])
+	ops.IsLast = buf[12] != 0
+	return
+}
+
+// Serialize marshals the given OnePassSignature to w.
+func (ops *OnePassSignature) Serialize(w io.Writer) os.Error {
+	var buf [13]byte
+	buf[0] = onePassSignatureVersion
+	buf[1] = uint8(ops.SigType)
+	var ok bool
+	buf[2], ok = s2k.HashToHashId(ops.Hash)
+	if !ok {
+		return error.UnsupportedError("hash type: " + strconv.Itoa(int(ops.Hash)))
+	}
+	buf[3] = uint8(ops.PubKeyAlgo)
+	binary.BigEndian.PutUint64(buf[4:12], ops.KeyId)
+	if ops.IsLast {
+		buf[12] = 1
+	}
+
+	if err := serializeHeader(w, packetTypeOnePassSignature, len(buf)); err != nil {
+		return err
+	}
+	_, err := w.Write(buf[:])
+	return err
+}
diff --git a/src/pkg/crypto/openpgp/packet/packet.go b/src/pkg/crypto/openpgp/packet/packet.go
new file mode 100644
index 000000000..1d7297e38
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/packet.go
@@ -0,0 +1,483 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package packet implements parsing and serialization of OpenPGP packets, as
+// specified in RFC 4880.
+package packet
+
+import (
+	"big"
+	"crypto/aes"
+	"crypto/cast5"
+	"crypto/cipher"
+	"crypto/openpgp/error"
+	"io"
+	"os"
+)
+
+// readFull is the same as io.ReadFull except that reading zero bytes returns
+// ErrUnexpectedEOF rather than EOF.
+func readFull(r io.Reader, buf []byte) (n int, err os.Error) {
+	n, err = io.ReadFull(r, buf)
+	if err == os.EOF {
+		err = io.ErrUnexpectedEOF
+	}
+	return
+}
+
+// readLength reads an OpenPGP length from r. See RFC 4880, section 4.2.2.
+func readLength(r io.Reader) (length int64, isPartial bool, err os.Error) {
+	var buf [4]byte
+	_, err = readFull(r, buf[:1])
+	if err != nil {
+		return
+	}
+	switch {
+	case buf[0] < 192:
+		length = int64(buf[0])
+	case buf[0] < 224:
+		length = int64(buf[0]-192) << 8
+		_, err = readFull(r, buf[0:1])
+		if err != nil {
+			return
+		}
+		length += int64(buf[0]) + 192
+	case buf[0] < 255:
+		length = int64(1) << (buf[0] & 0x1f)
+		isPartial = true
+	default:
+		_, err = readFull(r, buf[0:4])
+		if err != nil {
+			return
+		}
+		length = int64(buf[0])<<24 |
+			int64(buf[1])<<16 |
+			int64(buf[2])<<8 |
+			int64(buf[3])
+	}
+	return
+}
+
+// partialLengthReader wraps an io.Reader and handles OpenPGP partial lengths.
+// The continuation lengths are parsed and removed from the stream and EOF is
+// returned at the end of the packet. See RFC 4880, section 4.2.2.4.
+type partialLengthReader struct {
+	r         io.Reader
+	remaining int64
+	isPartial bool
+}
+
+func (r *partialLengthReader) Read(p []byte) (n int, err os.Error) {
+	for r.remaining == 0 {
+		if !r.isPartial {
+			return 0, os.EOF
+		}
+		r.remaining, r.isPartial, err = readLength(r.r)
+		if err != nil {
+			return 0, err
+		}
+	}
+
+	toRead := int64(len(p))
+	if toRead > r.remaining {
+		toRead = r.remaining
+	}
+
+	n, err = r.r.Read(p[:int(toRead)])
+	r.remaining -= int64(n)
+	if n < int(toRead) && err == os.EOF {
+		err = io.ErrUnexpectedEOF
+	}
+	return
+}
+
+// partialLengthWriter writes a stream of data using OpenPGP partial lengths.
+// See RFC 4880, section 4.2.2.4.
+type partialLengthWriter struct {
+	w          io.WriteCloser
+	lengthByte [1]byte
+}
+
+func (w *partialLengthWriter) Write(p []byte) (n int, err os.Error) {
+	for len(p) > 0 {
+		for power := uint(14); power < 32; power-- {
+			l := 1 << power
+			if len(p) >= l {
+				w.lengthByte[0] = 224 + uint8(power)
+				_, err = w.w.Write(w.lengthByte[:])
+				if err != nil {
+					return
+				}
+				var m int
+				m, err = w.w.Write(p[:l])
+				n += m
+				if err != nil {
+					return
+				}
+				p = p[l:]
+				break
+			}
+		}
+	}
+	return
+}
+
+func (w *partialLengthWriter) Close() os.Error {
+	w.lengthByte[0] = 0
+	_, err := w.w.Write(w.lengthByte[:])
+	if err != nil {
+		return err
+	}
+	return w.w.Close()
+}
+
+// A spanReader is an io.LimitReader, but it returns ErrUnexpectedEOF if the
+// underlying Reader returns EOF before the limit has been reached.
+type spanReader struct {
+	r io.Reader
+	n int64
+}
+
+func (l *spanReader) Read(p []byte) (n int, err os.Error) {
+	if l.n <= 0 {
+		return 0, os.EOF
+	}
+	if int64(len(p)) > l.n {
+		p = p[0:l.n]
+	}
+	n, err = l.r.Read(p)
+	l.n -= int64(n)
+	if l.n > 0 && err == os.EOF {
+		err = io.ErrUnexpectedEOF
+	}
+	return
+}
+
+// readHeader parses a packet header and returns an io.Reader which will return
+// the contents of the packet. See RFC 4880, section 4.2.
+func readHeader(r io.Reader) (tag packetType, length int64, contents io.Reader, err os.Error) {
+	var buf [4]byte
+	_, err = io.ReadFull(r, buf[:1])
+	if err != nil {
+		return
+	}
+	if buf[0]&0x80 == 0 {
+		err = error.StructuralError("tag byte does not have MSB set")
+		return
+	}
+	if buf[0]&0x40 == 0 {
+		// Old format packet
+		tag = packetType((buf[0] & 0x3f) >> 2)
+		lengthType := buf[0] & 3
+		if lengthType == 3 {
+			length = -1
+			contents = r
+			return
+		}
+		lengthBytes := 1 << lengthType
+		_, err = readFull(r, buf[0:lengthBytes])
+		if err != nil {
+			return
+		}
+		for i := 0; i < lengthBytes; i++ {
+			length <<= 8
+			length |= int64(buf[i])
+		}
+		contents = &spanReader{r, length}
+		return
+	}
+
+	// New format packet
+	tag = packetType(buf[0] & 0x3f)
+	length, isPartial, err := readLength(r)
+	if err != nil {
+		return
+	}
+	if isPartial {
+		contents = &partialLengthReader{
+			remaining: length,
+			isPartial: true,
+			r:         r,
+		}
+		length = -1
+	} else {
+		contents = &spanReader{r, length}
+	}
+	return
+}
+
+// serializeHeader writes an OpenPGP packet header to w. See RFC 4880, section
+// 4.2.
+func serializeHeader(w io.Writer, ptype packetType, length int) (err os.Error) {
+	var buf [6]byte
+	var n int
+
+	buf[0] = 0x80 | 0x40 | byte(ptype)
+	if length < 192 {
+		buf[1] = byte(length)
+		n = 2
+	} else if length < 8384 {
+		length -= 192
+		buf[1] = 192 + byte(length>>8)
+		buf[2] = byte(length)
+		n = 3
+	} else {
+		buf[1] = 255
+		buf[2] = byte(length >> 24)
+		buf[3] = byte(length >> 16)
+		buf[4] = byte(length >> 8)
+		buf[5] = byte(length)
+		n = 6
+	}
+
+	_, err = w.Write(buf[:n])
+	return
+}
+
+// serializeStreamHeader writes an OpenPGP packet header to w where the
+// length of the packet is unknown. It returns a io.WriteCloser which can be
+// used to write the contents of the packet. See RFC 4880, section 4.2.
+func serializeStreamHeader(w io.WriteCloser, ptype packetType) (out io.WriteCloser, err os.Error) {
+	var buf [1]byte
+	buf[0] = 0x80 | 0x40 | byte(ptype)
+	_, err = w.Write(buf[:])
+	if err != nil {
+		return
+	}
+	out = &partialLengthWriter{w: w}
+	return
+}
+
+// Packet represents an OpenPGP packet. Users are expected to try casting
+// instances of this interface to specific packet types.
+type Packet interface {
+	parse(io.Reader) os.Error
+}
+
+// consumeAll reads from the given Reader until error, returning the number of
+// bytes read.
+func consumeAll(r io.Reader) (n int64, err os.Error) {
+	var m int
+	var buf [1024]byte
+
+	for {
+		m, err = r.Read(buf[:])
+		n += int64(m)
+		if err == os.EOF {
+			err = nil
+			return
+		}
+		if err != nil {
+			return
+		}
+	}
+
+	panic("unreachable")
+}
+
+// packetType represents the numeric ids of the different OpenPGP packet types. See
+// http://www.iana.org/assignments/pgp-parameters/pgp-parameters.xhtml#pgp-parameters-2
+type packetType uint8
+
+const (
+	packetTypeEncryptedKey              packetType = 1
+	packetTypeSignature                 packetType = 2
+	packetTypeSymmetricKeyEncrypted     packetType = 3
+	packetTypeOnePassSignature          packetType = 4
+	packetTypePrivateKey                packetType = 5
+	packetTypePublicKey                 packetType = 6
+	packetTypePrivateSubkey             packetType = 7
+	packetTypeCompressed                packetType = 8
+	packetTypeSymmetricallyEncrypted    packetType = 9
+	packetTypeLiteralData               packetType = 11
+	packetTypeUserId                    packetType = 13
+	packetTypePublicSubkey              packetType = 14
+	packetTypeSymmetricallyEncryptedMDC packetType = 18
+)
+
+// Read reads a single OpenPGP packet from the given io.Reader. If there is an
+// error parsing a packet, the whole packet is consumed from the input.
+func Read(r io.Reader) (p Packet, err os.Error) {
+	tag, _, contents, err := readHeader(r)
+	if err != nil {
+		return
+	}
+
+	switch tag {
+	case packetTypeEncryptedKey:
+		p = new(EncryptedKey)
+	case packetTypeSignature:
+		p = new(Signature)
+	case packetTypeSymmetricKeyEncrypted:
+		p = new(SymmetricKeyEncrypted)
+	case packetTypeOnePassSignature:
+		p = new(OnePassSignature)
+	case packetTypePrivateKey, packetTypePrivateSubkey:
+		pk := new(PrivateKey)
+		if tag == packetTypePrivateSubkey {
+			pk.IsSubkey = true
+		}
+		p = pk
+	case packetTypePublicKey, packetTypePublicSubkey:
+		pk := new(PublicKey)
+		if tag == packetTypePublicSubkey {
+			pk.IsSubkey = true
+		}
+		p = pk
+	case packetTypeCompressed:
+		p = new(Compressed)
+	case packetTypeSymmetricallyEncrypted:
+		p = new(SymmetricallyEncrypted)
+	case packetTypeLiteralData:
+		p = new(LiteralData)
+	case packetTypeUserId:
+		p = new(UserId)
+	case packetTypeSymmetricallyEncryptedMDC:
+		se := new(SymmetricallyEncrypted)
+		se.MDC = true
+		p = se
+	default:
+		err = error.UnknownPacketTypeError(tag)
+	}
+	if p != nil {
+		err = p.parse(contents)
+	}
+	if err != nil {
+		consumeAll(contents)
+	}
+	return
+}
+
+// SignatureType represents the different semantic meanings of an OpenPGP
+// signature. See RFC 4880, section 5.2.1.
+type SignatureType uint8
+
+const (
+	SigTypeBinary        SignatureType = 0
+	SigTypeText                        = 1
+	SigTypeGenericCert                 = 0x10
+	SigTypePersonaCert                 = 0x11
+	SigTypeCasualCert                  = 0x12
+	SigTypePositiveCert                = 0x13
+	SigTypeSubkeyBinding               = 0x18
+)
+
+// PublicKeyAlgorithm represents the different public key system specified for
+// OpenPGP. See
+// http://www.iana.org/assignments/pgp-parameters/pgp-parameters.xhtml#pgp-parameters-12
+type PublicKeyAlgorithm uint8
+
+const (
+	PubKeyAlgoRSA            PublicKeyAlgorithm = 1
+	PubKeyAlgoRSAEncryptOnly PublicKeyAlgorithm = 2
+	PubKeyAlgoRSASignOnly    PublicKeyAlgorithm = 3
+	PubKeyAlgoElGamal        PublicKeyAlgorithm = 16
+	PubKeyAlgoDSA            PublicKeyAlgorithm = 17
+)
+
+// CanEncrypt returns true if it's possible to encrypt a message to a public
+// key of the given type.
+func (pka PublicKeyAlgorithm) CanEncrypt() bool {
+	switch pka {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoElGamal:
+		return true
+	}
+	return false
+}
+
+// CanSign returns true if it's possible for a public key of the given type to
+// sign a message.
+func (pka PublicKeyAlgorithm) CanSign() bool {
+	switch pka {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly, PubKeyAlgoDSA:
+		return true
+	}
+	return false
+}
+
+// CipherFunction represents the different block ciphers specified for OpenPGP. See
+// http://www.iana.org/assignments/pgp-parameters/pgp-parameters.xhtml#pgp-parameters-13
+type CipherFunction uint8
+
+const (
+	CipherCAST5  CipherFunction = 3
+	CipherAES128 CipherFunction = 7
+	CipherAES192 CipherFunction = 8
+	CipherAES256 CipherFunction = 9
+)
+
+// KeySize returns the key size, in bytes, of cipher.
+func (cipher CipherFunction) KeySize() int {
+	switch cipher {
+	case CipherCAST5:
+		return cast5.KeySize
+	case CipherAES128:
+		return 16
+	case CipherAES192:
+		return 24
+	case CipherAES256:
+		return 32
+	}
+	return 0
+}
+
+// blockSize returns the block size, in bytes, of cipher.
+func (cipher CipherFunction) blockSize() int {
+	switch cipher {
+	case CipherCAST5:
+		return 8
+	case CipherAES128, CipherAES192, CipherAES256:
+		return 16
+	}
+	return 0
+}
+
+// new returns a fresh instance of the given cipher.
+func (cipher CipherFunction) new(key []byte) (block cipher.Block) {
+	switch cipher {
+	case CipherCAST5:
+		block, _ = cast5.NewCipher(key)
+	case CipherAES128, CipherAES192, CipherAES256:
+		block, _ = aes.NewCipher(key)
+	}
+	return
+}
+
+// readMPI reads a big integer from r. The bit length returned is the bit
+// length that was specified in r. This is preserved so that the integer can be
+// reserialized exactly.
+func readMPI(r io.Reader) (mpi []byte, bitLength uint16, err os.Error) {
+	var buf [2]byte
+	_, err = readFull(r, buf[0:])
+	if err != nil {
+		return
+	}
+	bitLength = uint16(buf[0])<<8 | uint16(buf[1])
+	numBytes := (int(bitLength) + 7) / 8
+	mpi = make([]byte, numBytes)
+	_, err = readFull(r, mpi)
+	return
+}
+
+// mpiLength returns the length of the given *big.Int when serialized as an
+// MPI.
+func mpiLength(n *big.Int) (mpiLengthInBytes int) {
+	mpiLengthInBytes = 2 /* MPI length */
+	mpiLengthInBytes += (n.BitLen() + 7) / 8
+	return
+}
+
+// writeMPI serializes a big integer to w.
+func writeMPI(w io.Writer, bitLength uint16, mpiBytes []byte) (err os.Error) {
+	_, err = w.Write([]byte{byte(bitLength >> 8), byte(bitLength)})
+	if err == nil {
+		_, err = w.Write(mpiBytes)
+	}
+	return
+}
+
+// writeBig serializes a *big.Int to w.
+func writeBig(w io.Writer, i *big.Int) os.Error {
+	return writeMPI(w, uint16(i.BitLen()), i.Bytes())
+}
diff --git a/src/pkg/crypto/openpgp/packet/packet_test.go b/src/pkg/crypto/openpgp/packet/packet_test.go
new file mode 100644
index 000000000..23d9978ae
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/packet_test.go
@@ -0,0 +1,256 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"bytes"
+	"crypto/openpgp/error"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+func TestReadFull(t *testing.T) {
+	var out [4]byte
+
+	b := bytes.NewBufferString("foo")
+	n, err := readFull(b, out[:3])
+	if n != 3 || err != nil {
+		t.Errorf("full read failed n:%d err:%s", n, err)
+	}
+
+	b = bytes.NewBufferString("foo")
+	n, err = readFull(b, out[:4])
+	if n != 3 || err != io.ErrUnexpectedEOF {
+		t.Errorf("partial read failed n:%d err:%s", n, err)
+	}
+
+	b = bytes.NewBuffer(nil)
+	n, err = readFull(b, out[:3])
+	if n != 0 || err != io.ErrUnexpectedEOF {
+		t.Errorf("empty read failed n:%d err:%s", n, err)
+	}
+}
+
+func readerFromHex(s string) io.Reader {
+	data, err := hex.DecodeString(s)
+	if err != nil {
+		panic("readerFromHex: bad input")
+	}
+	return bytes.NewBuffer(data)
+}
+
+var readLengthTests = []struct {
+	hexInput  string
+	length    int64
+	isPartial bool
+	err       os.Error
+}{
+	{"", 0, false, io.ErrUnexpectedEOF},
+	{"1f", 31, false, nil},
+	{"c0", 0, false, io.ErrUnexpectedEOF},
+	{"c101", 256 + 1 + 192, false, nil},
+	{"e0", 1, true, nil},
+	{"e1", 2, true, nil},
+	{"e2", 4, true, nil},
+	{"ff", 0, false, io.ErrUnexpectedEOF},
+	{"ff00", 0, false, io.ErrUnexpectedEOF},
+	{"ff0000", 0, false, io.ErrUnexpectedEOF},
+	{"ff000000", 0, false, io.ErrUnexpectedEOF},
+	{"ff00000000", 0, false, nil},
+	{"ff01020304", 16909060, false, nil},
+}
+
+func TestReadLength(t *testing.T) {
+	for i, test := range readLengthTests {
+		length, isPartial, err := readLength(readerFromHex(test.hexInput))
+		if test.err != nil {
+			if err != test.err {
+				t.Errorf("%d: expected different error got:%s want:%s", i, err, test.err)
+			}
+			continue
+		}
+		if err != nil {
+			t.Errorf("%d: unexpected error: %s", i, err)
+			continue
+		}
+		if length != test.length || isPartial != test.isPartial {
+			t.Errorf("%d: bad result got:(%d,%t) want:(%d,%t)", i, length, isPartial, test.length, test.isPartial)
+		}
+	}
+}
+
+var partialLengthReaderTests = []struct {
+	hexInput  string
+	err       os.Error
+	hexOutput string
+}{
+	{"e0", io.ErrUnexpectedEOF, ""},
+	{"e001", io.ErrUnexpectedEOF, ""},
+	{"e0010102", nil, "0102"},
+	{"ff00000000", nil, ""},
+	{"e10102e1030400", nil, "01020304"},
+	{"e101", io.ErrUnexpectedEOF, ""},
+}
+
+func TestPartialLengthReader(t *testing.T) {
+	for i, test := range partialLengthReaderTests {
+		r := &partialLengthReader{readerFromHex(test.hexInput), 0, true}
+		out, err := ioutil.ReadAll(r)
+		if test.err != nil {
+			if err != test.err {
+				t.Errorf("%d: expected different error got:%s want:%s", i, err, test.err)
+			}
+			continue
+		}
+		if err != nil {
+			t.Errorf("%d: unexpected error: %s", i, err)
+			continue
+		}
+
+		got := fmt.Sprintf("%x", out)
+		if got != test.hexOutput {
+			t.Errorf("%d: got:%s want:%s", i, test.hexOutput, got)
+		}
+	}
+}
+
+var readHeaderTests = []struct {
+	hexInput        string
+	structuralError bool
+	unexpectedEOF   bool
+	tag             int
+	length          int64
+	hexOutput       string
+}{
+	{"", false, false, 0, 0, ""},
+	{"7f", true, false, 0, 0, ""},
+
+	// Old format headers
+	{"80", false, true, 0, 0, ""},
+	{"8001", false, true, 0, 1, ""},
+	{"800102", false, false, 0, 1, "02"},
+	{"81000102", false, false, 0, 1, "02"},
+	{"820000000102", false, false, 0, 1, "02"},
+	{"860000000102", false, false, 1, 1, "02"},
+	{"83010203", false, false, 0, -1, "010203"},
+
+	// New format headers
+	{"c0", false, true, 0, 0, ""},
+	{"c000", false, false, 0, 0, ""},
+	{"c00102", false, false, 0, 1, "02"},
+	{"c0020203", false, false, 0, 2, "0203"},
+	{"c00202", false, true, 0, 2, ""},
+	{"c3020203", false, false, 3, 2, "0203"},
+}
+
+func TestReadHeader(t *testing.T) {
+	for i, test := range readHeaderTests {
+		tag, length, contents, err := readHeader(readerFromHex(test.hexInput))
+		if test.structuralError {
+			if _, ok := err.(error.StructuralError); ok {
+				continue
+			}
+			t.Errorf("%d: expected StructuralError, got:%s", i, err)
+			continue
+		}
+		if err != nil {
+			if len(test.hexInput) == 0 && err == os.EOF {
+				continue
+			}
+			if !test.unexpectedEOF || err != io.ErrUnexpectedEOF {
+				t.Errorf("%d: unexpected error from readHeader: %s", i, err)
+			}
+			continue
+		}
+		if int(tag) != test.tag || length != test.length {
+			t.Errorf("%d: got:(%d,%d) want:(%d,%d)", i, int(tag), length, test.tag, test.length)
+			continue
+		}
+
+		body, err := ioutil.ReadAll(contents)
+		if err != nil {
+			if !test.unexpectedEOF || err != io.ErrUnexpectedEOF {
+				t.Errorf("%d: unexpected error from contents: %s", i, err)
+			}
+			continue
+		}
+		if test.unexpectedEOF {
+			t.Errorf("%d: expected ErrUnexpectedEOF from contents but got no error", i)
+			continue
+		}
+		got := fmt.Sprintf("%x", body)
+		if got != test.hexOutput {
+			t.Errorf("%d: got:%s want:%s", i, got, test.hexOutput)
+		}
+	}
+}
+
+func TestSerializeHeader(t *testing.T) {
+	tag := packetTypePublicKey
+	lengths := []int{0, 1, 2, 64, 192, 193, 8000, 8384, 8385, 10000}
+
+	for _, length := range lengths {
+		buf := bytes.NewBuffer(nil)
+		serializeHeader(buf, tag, length)
+		tag2, length2, _, err := readHeader(buf)
+		if err != nil {
+			t.Errorf("length %d, err: %s", length, err)
+		}
+		if tag2 != tag {
+			t.Errorf("length %d, tag incorrect (got %d, want %d)", length, tag2, tag)
+		}
+		if int(length2) != length {
+			t.Errorf("length %d, length incorrect (got %d)", length, length2)
+		}
+	}
+}
+
+func TestPartialLengths(t *testing.T) {
+	buf := bytes.NewBuffer(nil)
+	w := new(partialLengthWriter)
+	w.w = noOpCloser{buf}
+
+	const maxChunkSize = 64
+
+	var b [maxChunkSize]byte
+	var n uint8
+	for l := 1; l <= maxChunkSize; l++ {
+		for i := 0; i < l; i++ {
+			b[i] = n
+			n++
+		}
+		m, err := w.Write(b[:l])
+		if m != l {
+			t.Errorf("short write got: %d want: %d", m, l)
+		}
+		if err != nil {
+			t.Errorf("error from write: %s", err)
+		}
+	}
+	w.Close()
+
+	want := (maxChunkSize * (maxChunkSize + 1)) / 2
+	copyBuf := bytes.NewBuffer(nil)
+	r := &partialLengthReader{buf, 0, true}
+	m, err := io.Copy(copyBuf, r)
+	if m != int64(want) {
+		t.Errorf("short copy got: %d want: %d", m, want)
+	}
+	if err != nil {
+		t.Errorf("error from copy: %s", err)
+	}
+
+	copyBytes := copyBuf.Bytes()
+	for i := 0; i < want; i++ {
+		if copyBytes[i] != uint8(i) {
+			t.Errorf("bad pattern in copy at %d", i)
+			break
+		}
+	}
+}
diff --git a/src/pkg/crypto/openpgp/packet/private_key.go b/src/pkg/crypto/openpgp/packet/private_key.go
new file mode 100644
index 000000000..6f8133d98
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/private_key.go
@@ -0,0 +1,301 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"big"
+	"bytes"
+	"crypto/cipher"
+	"crypto/dsa"
+	"crypto/openpgp/elgamal"
+	"crypto/openpgp/error"
+	"crypto/openpgp/s2k"
+	"crypto/rsa"
+	"crypto/sha1"
+	"io"
+	"io/ioutil"
+	"os"
+	"strconv"
+)
+
+// PrivateKey represents a possibly encrypted private key. See RFC 4880,
+// section 5.5.3.
+type PrivateKey struct {
+	PublicKey
+	Encrypted     bool // if true then the private key is unavailable until Decrypt has been called.
+	encryptedData []byte
+	cipher        CipherFunction
+	s2k           func(out, in []byte)
+	PrivateKey    interface{} // An *rsa.PrivateKey.
+	sha1Checksum  bool
+	iv            []byte
+}
+
+func NewRSAPrivateKey(currentTimeSecs uint32, priv *rsa.PrivateKey, isSubkey bool) *PrivateKey {
+	pk := new(PrivateKey)
+	pk.PublicKey = *NewRSAPublicKey(currentTimeSecs, &priv.PublicKey, isSubkey)
+	pk.PrivateKey = priv
+	return pk
+}
+
+func (pk *PrivateKey) parse(r io.Reader) (err os.Error) {
+	err = (&pk.PublicKey).parse(r)
+	if err != nil {
+		return
+	}
+	var buf [1]byte
+	_, err = readFull(r, buf[:])
+	if err != nil {
+		return
+	}
+
+	s2kType := buf[0]
+
+	switch s2kType {
+	case 0:
+		pk.s2k = nil
+		pk.Encrypted = false
+	case 254, 255:
+		_, err = readFull(r, buf[:])
+		if err != nil {
+			return
+		}
+		pk.cipher = CipherFunction(buf[0])
+		pk.Encrypted = true
+		pk.s2k, err = s2k.Parse(r)
+		if err != nil {
+			return
+		}
+		if s2kType == 254 {
+			pk.sha1Checksum = true
+		}
+	default:
+		return error.UnsupportedError("deprecated s2k function in private key")
+	}
+
+	if pk.Encrypted {
+		blockSize := pk.cipher.blockSize()
+		if blockSize == 0 {
+			return error.UnsupportedError("unsupported cipher in private key: " + strconv.Itoa(int(pk.cipher)))
+		}
+		pk.iv = make([]byte, blockSize)
+		_, err = readFull(r, pk.iv)
+		if err != nil {
+			return
+		}
+	}
+
+	pk.encryptedData, err = ioutil.ReadAll(r)
+	if err != nil {
+		return
+	}
+
+	if !pk.Encrypted {
+		return pk.parsePrivateKey(pk.encryptedData)
+	}
+
+	return
+}
+
+func mod64kHash(d []byte) uint16 {
+	h := uint16(0)
+	for i := 0; i < len(d); i += 2 {
+		v := uint16(d[i]) << 8
+		if i+1 < len(d) {
+			v += uint16(d[i+1])
+		}
+		h += v
+	}
+	return h
+}
+
+func (pk *PrivateKey) Serialize(w io.Writer) (err os.Error) {
+	// TODO(agl): support encrypted private keys
+	buf := bytes.NewBuffer(nil)
+	err = pk.PublicKey.serializeWithoutHeaders(buf)
+	if err != nil {
+		return
+	}
+	buf.WriteByte(0 /* no encryption */ )
+
+	privateKeyBuf := bytes.NewBuffer(nil)
+
+	switch priv := pk.PrivateKey.(type) {
+	case *rsa.PrivateKey:
+		err = serializeRSAPrivateKey(privateKeyBuf, priv)
+	default:
+		err = error.InvalidArgumentError("non-RSA private key")
+	}
+	if err != nil {
+		return
+	}
+
+	ptype := packetTypePrivateKey
+	contents := buf.Bytes()
+	privateKeyBytes := privateKeyBuf.Bytes()
+	if pk.IsSubkey {
+		ptype = packetTypePrivateSubkey
+	}
+	err = serializeHeader(w, ptype, len(contents)+len(privateKeyBytes)+2)
+	if err != nil {
+		return
+	}
+	_, err = w.Write(contents)
+	if err != nil {
+		return
+	}
+	_, err = w.Write(privateKeyBytes)
+	if err != nil {
+		return
+	}
+
+	checksum := mod64kHash(privateKeyBytes)
+	var checksumBytes [2]byte
+	checksumBytes[0] = byte(checksum >> 8)
+	checksumBytes[1] = byte(checksum)
+	_, err = w.Write(checksumBytes[:])
+
+	return
+}
+
+func serializeRSAPrivateKey(w io.Writer, priv *rsa.PrivateKey) os.Error {
+	err := writeBig(w, priv.D)
+	if err != nil {
+		return err
+	}
+	err = writeBig(w, priv.Primes[1])
+	if err != nil {
+		return err
+	}
+	err = writeBig(w, priv.Primes[0])
+	if err != nil {
+		return err
+	}
+	return writeBig(w, priv.Precomputed.Qinv)
+}
+
+// Decrypt decrypts an encrypted private key using a passphrase.
+func (pk *PrivateKey) Decrypt(passphrase []byte) os.Error {
+	if !pk.Encrypted {
+		return nil
+	}
+
+	key := make([]byte, pk.cipher.KeySize())
+	pk.s2k(key, passphrase)
+	block := pk.cipher.new(key)
+	cfb := cipher.NewCFBDecrypter(block, pk.iv)
+
+	data := pk.encryptedData
+	cfb.XORKeyStream(data, data)
+
+	if pk.sha1Checksum {
+		if len(data) < sha1.Size {
+			return error.StructuralError("truncated private key data")
+		}
+		h := sha1.New()
+		h.Write(data[:len(data)-sha1.Size])
+		sum := h.Sum()
+		if !bytes.Equal(sum, data[len(data)-sha1.Size:]) {
+			return error.StructuralError("private key checksum failure")
+		}
+		data = data[:len(data)-sha1.Size]
+	} else {
+		if len(data) < 2 {
+			return error.StructuralError("truncated private key data")
+		}
+		var sum uint16
+		for i := 0; i < len(data)-2; i++ {
+			sum += uint16(data[i])
+		}
+		if data[len(data)-2] != uint8(sum>>8) ||
+			data[len(data)-1] != uint8(sum) {
+			return error.StructuralError("private key checksum failure")
+		}
+		data = data[:len(data)-2]
+	}
+
+	return pk.parsePrivateKey(data)
+}
+
+func (pk *PrivateKey) parsePrivateKey(data []byte) (err os.Error) {
+	switch pk.PublicKey.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly, PubKeyAlgoRSAEncryptOnly:
+		return pk.parseRSAPrivateKey(data)
+	case PubKeyAlgoDSA:
+		return pk.parseDSAPrivateKey(data)
+	case PubKeyAlgoElGamal:
+		return pk.parseElGamalPrivateKey(data)
+	}
+	panic("impossible")
+}
+
+func (pk *PrivateKey) parseRSAPrivateKey(data []byte) (err os.Error) {
+	rsaPub := pk.PublicKey.PublicKey.(*rsa.PublicKey)
+	rsaPriv := new(rsa.PrivateKey)
+	rsaPriv.PublicKey = *rsaPub
+
+	buf := bytes.NewBuffer(data)
+	d, _, err := readMPI(buf)
+	if err != nil {
+		return
+	}
+	p, _, err := readMPI(buf)
+	if err != nil {
+		return
+	}
+	q, _, err := readMPI(buf)
+	if err != nil {
+		return
+	}
+
+	rsaPriv.D = new(big.Int).SetBytes(d)
+	rsaPriv.Primes = make([]*big.Int, 2)
+	rsaPriv.Primes[0] = new(big.Int).SetBytes(p)
+	rsaPriv.Primes[1] = new(big.Int).SetBytes(q)
+	rsaPriv.Precompute()
+	pk.PrivateKey = rsaPriv
+	pk.Encrypted = false
+	pk.encryptedData = nil
+
+	return nil
+}
+
+func (pk *PrivateKey) parseDSAPrivateKey(data []byte) (err os.Error) {
+	dsaPub := pk.PublicKey.PublicKey.(*dsa.PublicKey)
+	dsaPriv := new(dsa.PrivateKey)
+	dsaPriv.PublicKey = *dsaPub
+
+	buf := bytes.NewBuffer(data)
+	x, _, err := readMPI(buf)
+	if err != nil {
+		return
+	}
+
+	dsaPriv.X = new(big.Int).SetBytes(x)
+	pk.PrivateKey = dsaPriv
+	pk.Encrypted = false
+	pk.encryptedData = nil
+
+	return nil
+}
+
+func (pk *PrivateKey) parseElGamalPrivateKey(data []byte) (err os.Error) {
+	pub := pk.PublicKey.PublicKey.(*elgamal.PublicKey)
+	priv := new(elgamal.PrivateKey)
+	priv.PublicKey = *pub
+
+	buf := bytes.NewBuffer(data)
+	x, _, err := readMPI(buf)
+	if err != nil {
+		return
+	}
+
+	priv.X = new(big.Int).SetBytes(x)
+	pk.PrivateKey = priv
+	pk.Encrypted = false
+	pk.encryptedData = nil
+
+	return nil
+}
diff --git a/src/pkg/crypto/openpgp/packet/private_key_test.go b/src/pkg/crypto/openpgp/packet/private_key_test.go
new file mode 100644
index 000000000..60eebaa6b
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/private_key_test.go
@@ -0,0 +1,57 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"testing"
+)
+
+var privateKeyTests = []struct {
+	privateKeyHex string
+	creationTime  uint32
+}{
+	{
+		privKeyRSAHex,
+		0x4cc349a8,
+	},
+	{
+		privKeyElGamalHex,
+		0x4df9ee1a,
+	},
+}
+
+func TestPrivateKeyRead(t *testing.T) {
+	for i, test := range privateKeyTests {
+		packet, err := Read(readerFromHex(test.privateKeyHex))
+		if err != nil {
+			t.Errorf("#%d: failed to parse: %s", i, err)
+			continue
+		}
+
+		privKey := packet.(*PrivateKey)
+
+		if !privKey.Encrypted {
+			t.Errorf("#%d: private key isn't encrypted", i)
+			continue
+		}
+
+		err = privKey.Decrypt([]byte("testing"))
+		if err != nil {
+			t.Errorf("#%d: failed to decrypt: %s", i, err)
+			continue
+		}
+
+		if privKey.CreationTime != test.creationTime || privKey.Encrypted {
+			t.Errorf("#%d: bad result, got: %#v", i, privKey)
+		}
+	}
+}
+
+// Generated with `gpg --export-secret-keys "Test Key 2"`
+const privKeyRSAHex = "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"
+
+// Generated by `gpg --export-secret-keys` followed by a manual extraction of
+// the ElGamal subkey from the packets.
+const privKeyElGamalHex = "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"
diff --git a/src/pkg/crypto/openpgp/packet/public_key.go b/src/pkg/crypto/openpgp/packet/public_key.go
new file mode 100644
index 000000000..e6b0ae5f3
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/public_key.go
@@ -0,0 +1,393 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"big"
+	"crypto/dsa"
+	"crypto/openpgp/elgamal"
+	"crypto/openpgp/error"
+	"crypto/rsa"
+	"crypto/sha1"
+	"encoding/binary"
+	"fmt"
+	"hash"
+	"io"
+	"os"
+	"strconv"
+)
+
+// PublicKey represents an OpenPGP public key. See RFC 4880, section 5.5.2.
+type PublicKey struct {
+	CreationTime uint32 // seconds since the epoch
+	PubKeyAlgo   PublicKeyAlgorithm
+	PublicKey    interface{} // Either a *rsa.PublicKey or *dsa.PublicKey
+	Fingerprint  [20]byte
+	KeyId        uint64
+	IsSubkey     bool
+
+	n, e, p, q, g, y parsedMPI
+}
+
+func fromBig(n *big.Int) parsedMPI {
+	return parsedMPI{
+		bytes:     n.Bytes(),
+		bitLength: uint16(n.BitLen()),
+	}
+}
+
+// NewRSAPublicKey returns a PublicKey that wraps the given rsa.PublicKey.
+func NewRSAPublicKey(creationTimeSecs uint32, pub *rsa.PublicKey, isSubkey bool) *PublicKey {
+	pk := &PublicKey{
+		CreationTime: creationTimeSecs,
+		PubKeyAlgo:   PubKeyAlgoRSA,
+		PublicKey:    pub,
+		IsSubkey:     isSubkey,
+		n:            fromBig(pub.N),
+		e:            fromBig(big.NewInt(int64(pub.E))),
+	}
+
+	pk.setFingerPrintAndKeyId()
+	return pk
+}
+
+func (pk *PublicKey) parse(r io.Reader) (err os.Error) {
+	// RFC 4880, section 5.5.2
+	var buf [6]byte
+	_, err = readFull(r, buf[:])
+	if err != nil {
+		return
+	}
+	if buf[0] != 4 {
+		return error.UnsupportedError("public key version")
+	}
+	pk.CreationTime = uint32(buf[1])<<24 | uint32(buf[2])<<16 | uint32(buf[3])<<8 | uint32(buf[4])
+	pk.PubKeyAlgo = PublicKeyAlgorithm(buf[5])
+	switch pk.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
+		err = pk.parseRSA(r)
+	case PubKeyAlgoDSA:
+		err = pk.parseDSA(r)
+	case PubKeyAlgoElGamal:
+		err = pk.parseElGamal(r)
+	default:
+		err = error.UnsupportedError("public key type: " + strconv.Itoa(int(pk.PubKeyAlgo)))
+	}
+	if err != nil {
+		return
+	}
+
+	pk.setFingerPrintAndKeyId()
+	return
+}
+
+func (pk *PublicKey) setFingerPrintAndKeyId() {
+	// RFC 4880, section 12.2
+	fingerPrint := sha1.New()
+	pk.SerializeSignaturePrefix(fingerPrint)
+	pk.serializeWithoutHeaders(fingerPrint)
+	copy(pk.Fingerprint[:], fingerPrint.Sum())
+	pk.KeyId = binary.BigEndian.Uint64(pk.Fingerprint[12:20])
+}
+
+// parseRSA parses RSA public key material from the given Reader. See RFC 4880,
+// section 5.5.2.
+func (pk *PublicKey) parseRSA(r io.Reader) (err os.Error) {
+	pk.n.bytes, pk.n.bitLength, err = readMPI(r)
+	if err != nil {
+		return
+	}
+	pk.e.bytes, pk.e.bitLength, err = readMPI(r)
+	if err != nil {
+		return
+	}
+
+	if len(pk.e.bytes) > 3 {
+		err = error.UnsupportedError("large public exponent")
+		return
+	}
+	rsa := &rsa.PublicKey{
+		N: new(big.Int).SetBytes(pk.n.bytes),
+		E: 0,
+	}
+	for i := 0; i < len(pk.e.bytes); i++ {
+		rsa.E <<= 8
+		rsa.E |= int(pk.e.bytes[i])
+	}
+	pk.PublicKey = rsa
+	return
+}
+
+// parseDSA parses DSA public key material from the given Reader. See RFC 4880,
+// section 5.5.2.
+func (pk *PublicKey) parseDSA(r io.Reader) (err os.Error) {
+	pk.p.bytes, pk.p.bitLength, err = readMPI(r)
+	if err != nil {
+		return
+	}
+	pk.q.bytes, pk.q.bitLength, err = readMPI(r)
+	if err != nil {
+		return
+	}
+	pk.g.bytes, pk.g.bitLength, err = readMPI(r)
+	if err != nil {
+		return
+	}
+	pk.y.bytes, pk.y.bitLength, err = readMPI(r)
+	if err != nil {
+		return
+	}
+
+	dsa := new(dsa.PublicKey)
+	dsa.P = new(big.Int).SetBytes(pk.p.bytes)
+	dsa.Q = new(big.Int).SetBytes(pk.q.bytes)
+	dsa.G = new(big.Int).SetBytes(pk.g.bytes)
+	dsa.Y = new(big.Int).SetBytes(pk.y.bytes)
+	pk.PublicKey = dsa
+	return
+}
+
+// parseElGamal parses ElGamal public key material from the given Reader. See
+// RFC 4880, section 5.5.2.
+func (pk *PublicKey) parseElGamal(r io.Reader) (err os.Error) {
+	pk.p.bytes, pk.p.bitLength, err = readMPI(r)
+	if err != nil {
+		return
+	}
+	pk.g.bytes, pk.g.bitLength, err = readMPI(r)
+	if err != nil {
+		return
+	}
+	pk.y.bytes, pk.y.bitLength, err = readMPI(r)
+	if err != nil {
+		return
+	}
+
+	elgamal := new(elgamal.PublicKey)
+	elgamal.P = new(big.Int).SetBytes(pk.p.bytes)
+	elgamal.G = new(big.Int).SetBytes(pk.g.bytes)
+	elgamal.Y = new(big.Int).SetBytes(pk.y.bytes)
+	pk.PublicKey = elgamal
+	return
+}
+
+// SerializeSignaturePrefix writes the prefix for this public key to the given Writer.
+// The prefix is used when calculating a signature over this public key. See
+// RFC 4880, section 5.2.4.
+func (pk *PublicKey) SerializeSignaturePrefix(h hash.Hash) {
+	var pLength uint16
+	switch pk.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
+		pLength += 2 + uint16(len(pk.n.bytes))
+		pLength += 2 + uint16(len(pk.e.bytes))
+	case PubKeyAlgoDSA:
+		pLength += 2 + uint16(len(pk.p.bytes))
+		pLength += 2 + uint16(len(pk.q.bytes))
+		pLength += 2 + uint16(len(pk.g.bytes))
+		pLength += 2 + uint16(len(pk.y.bytes))
+	case PubKeyAlgoElGamal:
+		pLength += 2 + uint16(len(pk.p.bytes))
+		pLength += 2 + uint16(len(pk.g.bytes))
+		pLength += 2 + uint16(len(pk.y.bytes))
+	default:
+		panic("unknown public key algorithm")
+	}
+	pLength += 6
+	h.Write([]byte{0x99, byte(pLength >> 8), byte(pLength)})
+	return
+}
+
+func (pk *PublicKey) Serialize(w io.Writer) (err os.Error) {
+	length := 6 // 6 byte header
+
+	switch pk.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
+		length += 2 + len(pk.n.bytes)
+		length += 2 + len(pk.e.bytes)
+	case PubKeyAlgoDSA:
+		length += 2 + len(pk.p.bytes)
+		length += 2 + len(pk.q.bytes)
+		length += 2 + len(pk.g.bytes)
+		length += 2 + len(pk.y.bytes)
+	case PubKeyAlgoElGamal:
+		length += 2 + len(pk.p.bytes)
+		length += 2 + len(pk.g.bytes)
+		length += 2 + len(pk.y.bytes)
+	default:
+		panic("unknown public key algorithm")
+	}
+
+	packetType := packetTypePublicKey
+	if pk.IsSubkey {
+		packetType = packetTypePublicSubkey
+	}
+	err = serializeHeader(w, packetType, length)
+	if err != nil {
+		return
+	}
+	return pk.serializeWithoutHeaders(w)
+}
+
+// serializeWithoutHeaders marshals the PublicKey to w in the form of an
+// OpenPGP public key packet, not including the packet header.
+func (pk *PublicKey) serializeWithoutHeaders(w io.Writer) (err os.Error) {
+	var buf [6]byte
+	buf[0] = 4
+	buf[1] = byte(pk.CreationTime >> 24)
+	buf[2] = byte(pk.CreationTime >> 16)
+	buf[3] = byte(pk.CreationTime >> 8)
+	buf[4] = byte(pk.CreationTime)
+	buf[5] = byte(pk.PubKeyAlgo)
+
+	_, err = w.Write(buf[:])
+	if err != nil {
+		return
+	}
+
+	switch pk.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
+		return writeMPIs(w, pk.n, pk.e)
+	case PubKeyAlgoDSA:
+		return writeMPIs(w, pk.p, pk.q, pk.g, pk.y)
+	case PubKeyAlgoElGamal:
+		return writeMPIs(w, pk.p, pk.g, pk.y)
+	}
+	return error.InvalidArgumentError("bad public-key algorithm")
+}
+
+// CanSign returns true iff this public key can generate signatures
+func (pk *PublicKey) CanSign() bool {
+	return pk.PubKeyAlgo != PubKeyAlgoRSAEncryptOnly && pk.PubKeyAlgo != PubKeyAlgoElGamal
+}
+
+// VerifySignature returns nil iff sig is a valid signature, made by this
+// public key, of the data hashed into signed. signed is mutated by this call.
+func (pk *PublicKey) VerifySignature(signed hash.Hash, sig *Signature) (err os.Error) {
+	if !pk.CanSign() {
+		return error.InvalidArgumentError("public key cannot generate signatures")
+	}
+
+	signed.Write(sig.HashSuffix)
+	hashBytes := signed.Sum()
+
+	if hashBytes[0] != sig.HashTag[0] || hashBytes[1] != sig.HashTag[1] {
+		return error.SignatureError("hash tag doesn't match")
+	}
+
+	if pk.PubKeyAlgo != sig.PubKeyAlgo {
+		return error.InvalidArgumentError("public key and signature use different algorithms")
+	}
+
+	switch pk.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
+		rsaPublicKey, _ := pk.PublicKey.(*rsa.PublicKey)
+		err = rsa.VerifyPKCS1v15(rsaPublicKey, sig.Hash, hashBytes, sig.RSASignature.bytes)
+		if err != nil {
+			return error.SignatureError("RSA verification failure")
+		}
+		return nil
+	case PubKeyAlgoDSA:
+		dsaPublicKey, _ := pk.PublicKey.(*dsa.PublicKey)
+		if !dsa.Verify(dsaPublicKey, hashBytes, new(big.Int).SetBytes(sig.DSASigR.bytes), new(big.Int).SetBytes(sig.DSASigS.bytes)) {
+			return error.SignatureError("DSA verification failure")
+		}
+		return nil
+	default:
+		panic("shouldn't happen")
+	}
+	panic("unreachable")
+}
+
+// keySignatureHash returns a Hash of the message that needs to be signed for
+// pk to assert a subkey relationship to signed.
+func keySignatureHash(pk, signed *PublicKey, sig *Signature) (h hash.Hash, err os.Error) {
+	h = sig.Hash.New()
+	if h == nil {
+		return nil, error.UnsupportedError("hash function")
+	}
+
+	// RFC 4880, section 5.2.4
+	pk.SerializeSignaturePrefix(h)
+	pk.serializeWithoutHeaders(h)
+	signed.SerializeSignaturePrefix(h)
+	signed.serializeWithoutHeaders(h)
+	return
+}
+
+// VerifyKeySignature returns nil iff sig is a valid signature, made by this
+// public key, of signed.
+func (pk *PublicKey) VerifyKeySignature(signed *PublicKey, sig *Signature) (err os.Error) {
+	h, err := keySignatureHash(pk, signed, sig)
+	if err != nil {
+		return err
+	}
+	return pk.VerifySignature(h, sig)
+}
+
+// userIdSignatureHash returns a Hash of the message that needs to be signed
+// to assert that pk is a valid key for id.
+func userIdSignatureHash(id string, pk *PublicKey, sig *Signature) (h hash.Hash, err os.Error) {
+	h = sig.Hash.New()
+	if h == nil {
+		return nil, error.UnsupportedError("hash function")
+	}
+
+	// RFC 4880, section 5.2.4
+	pk.SerializeSignaturePrefix(h)
+	pk.serializeWithoutHeaders(h)
+
+	var buf [5]byte
+	buf[0] = 0xb4
+	buf[1] = byte(len(id) >> 24)
+	buf[2] = byte(len(id) >> 16)
+	buf[3] = byte(len(id) >> 8)
+	buf[4] = byte(len(id))
+	h.Write(buf[:])
+	h.Write([]byte(id))
+
+	return
+}
+
+// VerifyUserIdSignature returns nil iff sig is a valid signature, made by this
+// public key, of id.
+func (pk *PublicKey) VerifyUserIdSignature(id string, sig *Signature) (err os.Error) {
+	h, err := userIdSignatureHash(id, pk, sig)
+	if err != nil {
+		return err
+	}
+	return pk.VerifySignature(h, sig)
+}
+
+// KeyIdString returns the public key's fingerprint in capital hex
+// (e.g. "6C7EE1B8621CC013").
+func (pk *PublicKey) KeyIdString() string {
+	return fmt.Sprintf("%X", pk.Fingerprint[12:20])
+}
+
+// KeyIdShortString returns the short form of public key's fingerprint
+// in capital hex, as shown by gpg --list-keys (e.g. "621CC013").
+func (pk *PublicKey) KeyIdShortString() string {
+	return fmt.Sprintf("%X", pk.Fingerprint[16:20])
+}
+
+// A parsedMPI is used to store the contents of a big integer, along with the
+// bit length that was specified in the original input. This allows the MPI to
+// be reserialized exactly.
+type parsedMPI struct {
+	bytes     []byte
+	bitLength uint16
+}
+
+// writeMPIs is a utility function for serializing several big integers to the
+// given Writer.
+func writeMPIs(w io.Writer, mpis ...parsedMPI) (err os.Error) {
+	for _, mpi := range mpis {
+		err = writeMPI(w, mpi.bitLength, mpi.bytes)
+		if err != nil {
+			return
+		}
+	}
+	return
+}
diff --git a/src/pkg/crypto/openpgp/packet/public_key_test.go b/src/pkg/crypto/openpgp/packet/public_key_test.go
new file mode 100644
index 000000000..6e8bfbce6
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/public_key_test.go
@@ -0,0 +1,98 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"bytes"
+	"encoding/hex"
+	"testing"
+)
+
+var pubKeyTests = []struct {
+	hexData        string
+	hexFingerprint string
+	creationTime   uint32
+	pubKeyAlgo     PublicKeyAlgorithm
+	keyId          uint64
+	keyIdString    string
+	keyIdShort     string
+}{
+	{rsaPkDataHex, rsaFingerprintHex, 0x4d3c5c10, PubKeyAlgoRSA, 0xa34d7e18c20c31bb, "A34D7E18C20C31BB", "C20C31BB"},
+	{dsaPkDataHex, dsaFingerprintHex, 0x4d432f89, PubKeyAlgoDSA, 0x8e8fbe54062f19ed, "8E8FBE54062F19ED", "062F19ED"},
+}
+
+func TestPublicKeyRead(t *testing.T) {
+	for i, test := range pubKeyTests {
+		packet, err := Read(readerFromHex(test.hexData))
+		if err != nil {
+			t.Errorf("#%d: Read error: %s", i, err)
+			continue
+		}
+		pk, ok := packet.(*PublicKey)
+		if !ok {
+			t.Errorf("#%d: failed to parse, got: %#v", i, packet)
+			continue
+		}
+		if pk.PubKeyAlgo != test.pubKeyAlgo {
+			t.Errorf("#%d: bad public key algorithm got:%x want:%x", i, pk.PubKeyAlgo, test.pubKeyAlgo)
+		}
+		if pk.CreationTime != test.creationTime {
+			t.Errorf("#%d: bad creation time got:%x want:%x", i, pk.CreationTime, test.creationTime)
+		}
+		expectedFingerprint, _ := hex.DecodeString(test.hexFingerprint)
+		if !bytes.Equal(expectedFingerprint, pk.Fingerprint[:]) {
+			t.Errorf("#%d: bad fingerprint got:%x want:%x", i, pk.Fingerprint[:], expectedFingerprint)
+		}
+		if pk.KeyId != test.keyId {
+			t.Errorf("#%d: bad keyid got:%x want:%x", i, pk.KeyId, test.keyId)
+		}
+		if g, e := pk.KeyIdString(), test.keyIdString; g != e {
+			t.Errorf("#%d: bad KeyIdString got:%q want:%q", i, g, e)
+		}
+		if g, e := pk.KeyIdShortString(), test.keyIdShort; g != e {
+			t.Errorf("#%d: bad KeyIdShortString got:%q want:%q", i, g, e)
+		}
+	}
+}
+
+func TestPublicKeySerialize(t *testing.T) {
+	for i, test := range pubKeyTests {
+		packet, err := Read(readerFromHex(test.hexData))
+		if err != nil {
+			t.Errorf("#%d: Read error: %s", i, err)
+			continue
+		}
+		pk, ok := packet.(*PublicKey)
+		if !ok {
+			t.Errorf("#%d: failed to parse, got: %#v", i, packet)
+			continue
+		}
+		serializeBuf := bytes.NewBuffer(nil)
+		err = pk.Serialize(serializeBuf)
+		if err != nil {
+			t.Errorf("#%d: failed to serialize: %s", i, err)
+			continue
+		}
+
+		packet, err = Read(serializeBuf)
+		if err != nil {
+			t.Errorf("#%d: Read error (from serialized data): %s", i, err)
+			continue
+		}
+		pk, ok = packet.(*PublicKey)
+		if !ok {
+			t.Errorf("#%d: failed to parse serialized data, got: %#v", i, packet)
+			continue
+		}
+	}
+}
+
+const rsaFingerprintHex = "5fb74b1d03b1e3cb31bc2f8aa34d7e18c20c31bb"
+
+const rsaPkDataHex = "988d044d3c5c10010400b1d13382944bd5aba23a4312968b5095d14f947f600eb478e14a6fcb16b0e0cac764884909c020bc495cfcc39a935387c661507bdb236a0612fb582cac3af9b29cc2c8c70090616c41b662f4da4c1201e195472eb7f4ae1ccbcbf9940fe21d985e379a5563dde5b9a23d35f1cfaa5790da3b79db26f23695107bfaca8e7b5bcd0011010001"
+
+const dsaFingerprintHex = "eece4c094db002103714c63c8e8fbe54062f19ed"
+
+const dsaPkDataHex = "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"
diff --git a/src/pkg/crypto/openpgp/packet/reader.go b/src/pkg/crypto/openpgp/packet/reader.go
new file mode 100644
index 000000000..5febc3bc8
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/reader.go
@@ -0,0 +1,63 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"crypto/openpgp/error"
+	"io"
+	"os"
+)
+
+// Reader reads packets from an io.Reader and allows packets to be 'unread' so
+// that they result from the next call to Next.
+type Reader struct {
+	q       []Packet
+	readers []io.Reader
+}
+
+// Next returns the most recently unread Packet, or reads another packet from
+// the top-most io.Reader. Unknown packet types are skipped.
+func (r *Reader) Next() (p Packet, err os.Error) {
+	if len(r.q) > 0 {
+		p = r.q[len(r.q)-1]
+		r.q = r.q[:len(r.q)-1]
+		return
+	}
+
+	for len(r.readers) > 0 {
+		p, err = Read(r.readers[len(r.readers)-1])
+		if err == nil {
+			return
+		}
+		if err == os.EOF {
+			r.readers = r.readers[:len(r.readers)-1]
+			continue
+		}
+		if _, ok := err.(error.UnknownPacketTypeError); !ok {
+			return nil, err
+		}
+	}
+
+	return nil, os.EOF
+}
+
+// Push causes the Reader to start reading from a new io.Reader. When an EOF
+// error is seen from the new io.Reader, it is popped and the Reader continues
+// to read from the next most recent io.Reader.
+func (r *Reader) Push(reader io.Reader) {
+	r.readers = append(r.readers, reader)
+}
+
+// Unread causes the given Packet to be returned from the next call to Next.
+func (r *Reader) Unread(p Packet) {
+	r.q = append(r.q, p)
+}
+
+func NewReader(r io.Reader) *Reader {
+	return &Reader{
+		q:       nil,
+		readers: []io.Reader{r},
+	}
+}
diff --git a/src/pkg/crypto/openpgp/packet/signature.go b/src/pkg/crypto/openpgp/packet/signature.go
new file mode 100644
index 000000000..7577e2875
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/signature.go
@@ -0,0 +1,558 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"crypto"
+	"crypto/dsa"
+	"crypto/openpgp/error"
+	"crypto/openpgp/s2k"
+	"crypto/rand"
+	"crypto/rsa"
+	"encoding/binary"
+	"hash"
+	"io"
+	"os"
+	"strconv"
+)
+
+// Signature represents a signature. See RFC 4880, section 5.2.
+type Signature struct {
+	SigType    SignatureType
+	PubKeyAlgo PublicKeyAlgorithm
+	Hash       crypto.Hash
+
+	// HashSuffix is extra data that is hashed in after the signed data.
+	HashSuffix []byte
+	// HashTag contains the first two bytes of the hash for fast rejection
+	// of bad signed data.
+	HashTag      [2]byte
+	CreationTime uint32 // Unix epoch time
+
+	RSASignature     parsedMPI
+	DSASigR, DSASigS parsedMPI
+
+	// rawSubpackets contains the unparsed subpackets, in order.
+	rawSubpackets []outputSubpacket
+
+	// The following are optional so are nil when not included in the
+	// signature.
+
+	SigLifetimeSecs, KeyLifetimeSecs                        *uint32
+	PreferredSymmetric, PreferredHash, PreferredCompression []uint8
+	IssuerKeyId                                             *uint64
+	IsPrimaryId                                             *bool
+
+	// FlagsValid is set if any flags were given. See RFC 4880, section
+	// 5.2.3.21 for details.
+	FlagsValid                                                           bool
+	FlagCertify, FlagSign, FlagEncryptCommunications, FlagEncryptStorage bool
+
+	outSubpackets []outputSubpacket
+}
+
+func (sig *Signature) parse(r io.Reader) (err os.Error) {
+	// RFC 4880, section 5.2.3
+	var buf [5]byte
+	_, err = readFull(r, buf[:1])
+	if err != nil {
+		return
+	}
+	if buf[0] != 4 {
+		err = error.UnsupportedError("signature packet version " + strconv.Itoa(int(buf[0])))
+		return
+	}
+
+	_, err = readFull(r, buf[:5])
+	if err != nil {
+		return
+	}
+	sig.SigType = SignatureType(buf[0])
+	sig.PubKeyAlgo = PublicKeyAlgorithm(buf[1])
+	switch sig.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly, PubKeyAlgoDSA:
+	default:
+		err = error.UnsupportedError("public key algorithm " + strconv.Itoa(int(sig.PubKeyAlgo)))
+		return
+	}
+
+	var ok bool
+	sig.Hash, ok = s2k.HashIdToHash(buf[2])
+	if !ok {
+		return error.UnsupportedError("hash function " + strconv.Itoa(int(buf[2])))
+	}
+
+	hashedSubpacketsLength := int(buf[3])<<8 | int(buf[4])
+	l := 6 + hashedSubpacketsLength
+	sig.HashSuffix = make([]byte, l+6)
+	sig.HashSuffix[0] = 4
+	copy(sig.HashSuffix[1:], buf[:5])
+	hashedSubpackets := sig.HashSuffix[6:l]
+	_, err = readFull(r, hashedSubpackets)
+	if err != nil {
+		return
+	}
+	// See RFC 4880, section 5.2.4
+	trailer := sig.HashSuffix[l:]
+	trailer[0] = 4
+	trailer[1] = 0xff
+	trailer[2] = uint8(l >> 24)
+	trailer[3] = uint8(l >> 16)
+	trailer[4] = uint8(l >> 8)
+	trailer[5] = uint8(l)
+
+	err = parseSignatureSubpackets(sig, hashedSubpackets, true)
+	if err != nil {
+		return
+	}
+
+	_, err = readFull(r, buf[:2])
+	if err != nil {
+		return
+	}
+	unhashedSubpacketsLength := int(buf[0])<<8 | int(buf[1])
+	unhashedSubpackets := make([]byte, unhashedSubpacketsLength)
+	_, err = readFull(r, unhashedSubpackets)
+	if err != nil {
+		return
+	}
+	err = parseSignatureSubpackets(sig, unhashedSubpackets, false)
+	if err != nil {
+		return
+	}
+
+	_, err = readFull(r, sig.HashTag[:2])
+	if err != nil {
+		return
+	}
+
+	switch sig.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
+		sig.RSASignature.bytes, sig.RSASignature.bitLength, err = readMPI(r)
+	case PubKeyAlgoDSA:
+		sig.DSASigR.bytes, sig.DSASigR.bitLength, err = readMPI(r)
+		if err == nil {
+			sig.DSASigS.bytes, sig.DSASigS.bitLength, err = readMPI(r)
+		}
+	default:
+		panic("unreachable")
+	}
+	return
+}
+
+// parseSignatureSubpackets parses subpackets of the main signature packet. See
+// RFC 4880, section 5.2.3.1.
+func parseSignatureSubpackets(sig *Signature, subpackets []byte, isHashed bool) (err os.Error) {
+	for len(subpackets) > 0 {
+		subpackets, err = parseSignatureSubpacket(sig, subpackets, isHashed)
+		if err != nil {
+			return
+		}
+	}
+
+	if sig.CreationTime == 0 {
+		err = error.StructuralError("no creation time in signature")
+	}
+
+	return
+}
+
+type signatureSubpacketType uint8
+
+const (
+	creationTimeSubpacket        signatureSubpacketType = 2
+	signatureExpirationSubpacket signatureSubpacketType = 3
+	keyExpirySubpacket           signatureSubpacketType = 9
+	prefSymmetricAlgosSubpacket  signatureSubpacketType = 11
+	issuerSubpacket              signatureSubpacketType = 16
+	prefHashAlgosSubpacket       signatureSubpacketType = 21
+	prefCompressionSubpacket     signatureSubpacketType = 22
+	primaryUserIdSubpacket       signatureSubpacketType = 25
+	keyFlagsSubpacket            signatureSubpacketType = 27
+)
+
+// parseSignatureSubpacket parses a single subpacket. len(subpacket) is >= 1.
+func parseSignatureSubpacket(sig *Signature, subpacket []byte, isHashed bool) (rest []byte, err os.Error) {
+	// RFC 4880, section 5.2.3.1
+	var (
+		length     uint32
+		packetType signatureSubpacketType
+		isCritical bool
+	)
+	switch {
+	case subpacket[0] < 192:
+		length = uint32(subpacket[0])
+		subpacket = subpacket[1:]
+	case subpacket[0] < 255:
+		if len(subpacket) < 2 {
+			goto Truncated
+		}
+		length = uint32(subpacket[0]-192)<<8 + uint32(subpacket[1]) + 192
+		subpacket = subpacket[2:]
+	default:
+		if len(subpacket) < 5 {
+			goto Truncated
+		}
+		length = uint32(subpacket[1])<<24 |
+			uint32(subpacket[2])<<16 |
+			uint32(subpacket[3])<<8 |
+			uint32(subpacket[4])
+		subpacket = subpacket[5:]
+	}
+	if length > uint32(len(subpacket)) {
+		goto Truncated
+	}
+	rest = subpacket[length:]
+	subpacket = subpacket[:length]
+	if len(subpacket) == 0 {
+		err = error.StructuralError("zero length signature subpacket")
+		return
+	}
+	packetType = signatureSubpacketType(subpacket[0] & 0x7f)
+	isCritical = subpacket[0]&0x80 == 0x80
+	subpacket = subpacket[1:]
+	sig.rawSubpackets = append(sig.rawSubpackets, outputSubpacket{isHashed, packetType, isCritical, subpacket})
+	switch packetType {
+	case creationTimeSubpacket:
+		if !isHashed {
+			err = error.StructuralError("signature creation time in non-hashed area")
+			return
+		}
+		if len(subpacket) != 4 {
+			err = error.StructuralError("signature creation time not four bytes")
+			return
+		}
+		sig.CreationTime = binary.BigEndian.Uint32(subpacket)
+	case signatureExpirationSubpacket:
+		// Signature expiration time, section 5.2.3.10
+		if !isHashed {
+			return
+		}
+		if len(subpacket) != 4 {
+			err = error.StructuralError("expiration subpacket with bad length")
+			return
+		}
+		sig.SigLifetimeSecs = new(uint32)
+		*sig.SigLifetimeSecs = binary.BigEndian.Uint32(subpacket)
+	case keyExpirySubpacket:
+		// Key expiration time, section 5.2.3.6
+		if !isHashed {
+			return
+		}
+		if len(subpacket) != 4 {
+			err = error.StructuralError("key expiration subpacket with bad length")
+			return
+		}
+		sig.KeyLifetimeSecs = new(uint32)
+		*sig.KeyLifetimeSecs = binary.BigEndian.Uint32(subpacket)
+	case prefSymmetricAlgosSubpacket:
+		// Preferred symmetric algorithms, section 5.2.3.7
+		if !isHashed {
+			return
+		}
+		sig.PreferredSymmetric = make([]byte, len(subpacket))
+		copy(sig.PreferredSymmetric, subpacket)
+	case issuerSubpacket:
+		// Issuer, section 5.2.3.5
+		if len(subpacket) != 8 {
+			err = error.StructuralError("issuer subpacket with bad length")
+			return
+		}
+		sig.IssuerKeyId = new(uint64)
+		*sig.IssuerKeyId = binary.BigEndian.Uint64(subpacket)
+	case prefHashAlgosSubpacket:
+		// Preferred hash algorithms, section 5.2.3.8
+		if !isHashed {
+			return
+		}
+		sig.PreferredHash = make([]byte, len(subpacket))
+		copy(sig.PreferredHash, subpacket)
+	case prefCompressionSubpacket:
+		// Preferred compression algorithms, section 5.2.3.9
+		if !isHashed {
+			return
+		}
+		sig.PreferredCompression = make([]byte, len(subpacket))
+		copy(sig.PreferredCompression, subpacket)
+	case primaryUserIdSubpacket:
+		// Primary User ID, section 5.2.3.19
+		if !isHashed {
+			return
+		}
+		if len(subpacket) != 1 {
+			err = error.StructuralError("primary user id subpacket with bad length")
+			return
+		}
+		sig.IsPrimaryId = new(bool)
+		if subpacket[0] > 0 {
+			*sig.IsPrimaryId = true
+		}
+	case keyFlagsSubpacket:
+		// Key flags, section 5.2.3.21
+		if !isHashed {
+			return
+		}
+		if len(subpacket) == 0 {
+			err = error.StructuralError("empty key flags subpacket")
+			return
+		}
+		sig.FlagsValid = true
+		if subpacket[0]&1 != 0 {
+			sig.FlagCertify = true
+		}
+		if subpacket[0]&2 != 0 {
+			sig.FlagSign = true
+		}
+		if subpacket[0]&4 != 0 {
+			sig.FlagEncryptCommunications = true
+		}
+		if subpacket[0]&8 != 0 {
+			sig.FlagEncryptStorage = true
+		}
+
+	default:
+		if isCritical {
+			err = error.UnsupportedError("unknown critical signature subpacket type " + strconv.Itoa(int(packetType)))
+			return
+		}
+	}
+	return
+
+Truncated:
+	err = error.StructuralError("signature subpacket truncated")
+	return
+}
+
+// subpacketLengthLength returns the length, in bytes, of an encoded length value.
+func subpacketLengthLength(length int) int {
+	if length < 192 {
+		return 1
+	}
+	if length < 16320 {
+		return 2
+	}
+	return 5
+}
+
+// serializeSubpacketLength marshals the given length into to.
+func serializeSubpacketLength(to []byte, length int) int {
+	if length < 192 {
+		to[0] = byte(length)
+		return 1
+	}
+	if length < 16320 {
+		length -= 192
+		to[0] = byte(length >> 8)
+		to[1] = byte(length)
+		return 2
+	}
+	to[0] = 255
+	to[1] = byte(length >> 24)
+	to[2] = byte(length >> 16)
+	to[3] = byte(length >> 8)
+	to[4] = byte(length)
+	return 5
+}
+
+// subpacketsLength returns the serialized length, in bytes, of the given
+// subpackets.
+func subpacketsLength(subpackets []outputSubpacket, hashed bool) (length int) {
+	for _, subpacket := range subpackets {
+		if subpacket.hashed == hashed {
+			length += subpacketLengthLength(len(subpacket.contents) + 1)
+			length += 1 // type byte
+			length += len(subpacket.contents)
+		}
+	}
+	return
+}
+
+// serializeSubpackets marshals the given subpackets into to.
+func serializeSubpackets(to []byte, subpackets []outputSubpacket, hashed bool) {
+	for _, subpacket := range subpackets {
+		if subpacket.hashed == hashed {
+			n := serializeSubpacketLength(to, len(subpacket.contents)+1)
+			to[n] = byte(subpacket.subpacketType)
+			to = to[1+n:]
+			n = copy(to, subpacket.contents)
+			to = to[n:]
+		}
+	}
+	return
+}
+
+// buildHashSuffix constructs the HashSuffix member of sig in preparation for signing.
+func (sig *Signature) buildHashSuffix() (err os.Error) {
+	hashedSubpacketsLen := subpacketsLength(sig.outSubpackets, true)
+
+	var ok bool
+	l := 6 + hashedSubpacketsLen
+	sig.HashSuffix = make([]byte, l+6)
+	sig.HashSuffix[0] = 4
+	sig.HashSuffix[1] = uint8(sig.SigType)
+	sig.HashSuffix[2] = uint8(sig.PubKeyAlgo)
+	sig.HashSuffix[3], ok = s2k.HashToHashId(sig.Hash)
+	if !ok {
+		sig.HashSuffix = nil
+		return error.InvalidArgumentError("hash cannot be represented in OpenPGP: " + strconv.Itoa(int(sig.Hash)))
+	}
+	sig.HashSuffix[4] = byte(hashedSubpacketsLen >> 8)
+	sig.HashSuffix[5] = byte(hashedSubpacketsLen)
+	serializeSubpackets(sig.HashSuffix[6:l], sig.outSubpackets, true)
+	trailer := sig.HashSuffix[l:]
+	trailer[0] = 4
+	trailer[1] = 0xff
+	trailer[2] = byte(l >> 24)
+	trailer[3] = byte(l >> 16)
+	trailer[4] = byte(l >> 8)
+	trailer[5] = byte(l)
+	return
+}
+
+func (sig *Signature) signPrepareHash(h hash.Hash) (digest []byte, err os.Error) {
+	err = sig.buildHashSuffix()
+	if err != nil {
+		return
+	}
+
+	h.Write(sig.HashSuffix)
+	digest = h.Sum()
+	copy(sig.HashTag[:], digest)
+	return
+}
+
+// Sign signs a message with a private key. The hash, h, must contain
+// the hash of the message to be signed and will be mutated by this function.
+// On success, the signature is stored in sig. Call Serialize to write it out.
+func (sig *Signature) Sign(h hash.Hash, priv *PrivateKey) (err os.Error) {
+	sig.outSubpackets = sig.buildSubpackets()
+	digest, err := sig.signPrepareHash(h)
+	if err != nil {
+		return
+	}
+
+	switch priv.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
+		sig.RSASignature.bytes, err = rsa.SignPKCS1v15(rand.Reader, priv.PrivateKey.(*rsa.PrivateKey), sig.Hash, digest)
+		sig.RSASignature.bitLength = uint16(8 * len(sig.RSASignature.bytes))
+	case PubKeyAlgoDSA:
+		r, s, err := dsa.Sign(rand.Reader, priv.PrivateKey.(*dsa.PrivateKey), digest)
+		if err == nil {
+			sig.DSASigR.bytes = r.Bytes()
+			sig.DSASigR.bitLength = uint16(8 * len(sig.DSASigR.bytes))
+			sig.DSASigS.bytes = s.Bytes()
+			sig.DSASigS.bitLength = uint16(8 * len(sig.DSASigS.bytes))
+		}
+	default:
+		err = error.UnsupportedError("public key algorithm: " + strconv.Itoa(int(sig.PubKeyAlgo)))
+	}
+
+	return
+}
+
+// SignUserId computes a signature from priv, asserting that pub is a valid
+// key for the identity id.  On success, the signature is stored in sig. Call
+// Serialize to write it out.
+func (sig *Signature) SignUserId(id string, pub *PublicKey, priv *PrivateKey) os.Error {
+	h, err := userIdSignatureHash(id, pub, sig)
+	if err != nil {
+		return nil
+	}
+	return sig.Sign(h, priv)
+}
+
+// SignKey computes a signature from priv, asserting that pub is a subkey.  On
+// success, the signature is stored in sig. Call Serialize to write it out.
+func (sig *Signature) SignKey(pub *PublicKey, priv *PrivateKey) os.Error {
+	h, err := keySignatureHash(&priv.PublicKey, pub, sig)
+	if err != nil {
+		return err
+	}
+	return sig.Sign(h, priv)
+}
+
+// Serialize marshals sig to w. SignRSA or SignDSA must have been called first.
+func (sig *Signature) Serialize(w io.Writer) (err os.Error) {
+	if len(sig.outSubpackets) == 0 {
+		sig.outSubpackets = sig.rawSubpackets
+	}
+	if sig.RSASignature.bytes == nil && sig.DSASigR.bytes == nil {
+		return error.InvalidArgumentError("Signature: need to call SignRSA or SignDSA before Serialize")
+	}
+
+	sigLength := 0
+	switch sig.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
+		sigLength = 2 + len(sig.RSASignature.bytes)
+	case PubKeyAlgoDSA:
+		sigLength = 2 + len(sig.DSASigR.bytes)
+		sigLength += 2 + len(sig.DSASigS.bytes)
+	default:
+		panic("impossible")
+	}
+
+	unhashedSubpacketsLen := subpacketsLength(sig.outSubpackets, false)
+	length := len(sig.HashSuffix) - 6 /* trailer not included */ +
+		2 /* length of unhashed subpackets */ + unhashedSubpacketsLen +
+		2 /* hash tag */ + sigLength
+	err = serializeHeader(w, packetTypeSignature, length)
+	if err != nil {
+		return
+	}
+
+	_, err = w.Write(sig.HashSuffix[:len(sig.HashSuffix)-6])
+	if err != nil {
+		return
+	}
+
+	unhashedSubpackets := make([]byte, 2+unhashedSubpacketsLen)
+	unhashedSubpackets[0] = byte(unhashedSubpacketsLen >> 8)
+	unhashedSubpackets[1] = byte(unhashedSubpacketsLen)
+	serializeSubpackets(unhashedSubpackets[2:], sig.outSubpackets, false)
+
+	_, err = w.Write(unhashedSubpackets)
+	if err != nil {
+		return
+	}
+	_, err = w.Write(sig.HashTag[:])
+	if err != nil {
+		return
+	}
+
+	switch sig.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
+		err = writeMPIs(w, sig.RSASignature)
+	case PubKeyAlgoDSA:
+		err = writeMPIs(w, sig.DSASigR, sig.DSASigS)
+	default:
+		panic("impossible")
+	}
+	return
+}
+
+// outputSubpacket represents a subpacket to be marshaled.
+type outputSubpacket struct {
+	hashed        bool // true if this subpacket is in the hashed area.
+	subpacketType signatureSubpacketType
+	isCritical    bool
+	contents      []byte
+}
+
+func (sig *Signature) buildSubpackets() (subpackets []outputSubpacket) {
+	creationTime := make([]byte, 4)
+	creationTime[0] = byte(sig.CreationTime >> 24)
+	creationTime[1] = byte(sig.CreationTime >> 16)
+	creationTime[2] = byte(sig.CreationTime >> 8)
+	creationTime[3] = byte(sig.CreationTime)
+	subpackets = append(subpackets, outputSubpacket{true, creationTimeSubpacket, false, creationTime})
+
+	if sig.IssuerKeyId != nil {
+		keyId := make([]byte, 8)
+		binary.BigEndian.PutUint64(keyId, *sig.IssuerKeyId)
+		subpackets = append(subpackets, outputSubpacket{true, issuerSubpacket, false, keyId})
+	}
+
+	return
+}
diff --git a/src/pkg/crypto/openpgp/packet/signature_test.go b/src/pkg/crypto/openpgp/packet/signature_test.go
new file mode 100644
index 000000000..c1bbde8b0
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/signature_test.go
@@ -0,0 +1,42 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"bytes"
+	"crypto"
+	"encoding/hex"
+	"testing"
+)
+
+func TestSignatureRead(t *testing.T) {
+	packet, err := Read(readerFromHex(signatureDataHex))
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	sig, ok := packet.(*Signature)
+	if !ok || sig.SigType != SigTypeBinary || sig.PubKeyAlgo != PubKeyAlgoRSA || sig.Hash != crypto.SHA1 {
+		t.Errorf("failed to parse, got: %#v", packet)
+	}
+}
+
+func TestSignatureReserialize(t *testing.T) {
+	packet, _ := Read(readerFromHex(signatureDataHex))
+	sig := packet.(*Signature)
+	out := new(bytes.Buffer)
+	err := sig.Serialize(out)
+	if err != nil {
+		t.Errorf("error reserializing: %s", err)
+		return
+	}
+
+	expected, _ := hex.DecodeString(signatureDataHex)
+	if !bytes.Equal(expected, out.Bytes()) {
+		t.Errorf("output doesn't match input (got vs expected):\n%s\n%s", hex.Dump(out.Bytes()), hex.Dump(expected))
+	}
+}
+
+const signatureDataHex = "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"
diff --git a/src/pkg/crypto/openpgp/packet/symmetric_key_encrypted.go b/src/pkg/crypto/openpgp/packet/symmetric_key_encrypted.go
new file mode 100644
index 000000000..ad4f1d621
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/symmetric_key_encrypted.go
@@ -0,0 +1,162 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"bytes"
+	"crypto/cipher"
+	"crypto/openpgp/error"
+	"crypto/openpgp/s2k"
+	"io"
+	"os"
+	"strconv"
+)
+
+// This is the largest session key that we'll support. Since no 512-bit cipher
+// has even been seriously used, this is comfortably large.
+const maxSessionKeySizeInBytes = 64
+
+// SymmetricKeyEncrypted represents a passphrase protected session key. See RFC
+// 4880, section 5.3.
+type SymmetricKeyEncrypted struct {
+	CipherFunc   CipherFunction
+	Encrypted    bool
+	Key          []byte // Empty unless Encrypted is false.
+	s2k          func(out, in []byte)
+	encryptedKey []byte
+}
+
+const symmetricKeyEncryptedVersion = 4
+
+func (ske *SymmetricKeyEncrypted) parse(r io.Reader) (err os.Error) {
+	// RFC 4880, section 5.3.
+	var buf [2]byte
+	_, err = readFull(r, buf[:])
+	if err != nil {
+		return
+	}
+	if buf[0] != symmetricKeyEncryptedVersion {
+		return error.UnsupportedError("SymmetricKeyEncrypted version")
+	}
+	ske.CipherFunc = CipherFunction(buf[1])
+
+	if ske.CipherFunc.KeySize() == 0 {
+		return error.UnsupportedError("unknown cipher: " + strconv.Itoa(int(buf[1])))
+	}
+
+	ske.s2k, err = s2k.Parse(r)
+	if err != nil {
+		return
+	}
+
+	encryptedKey := make([]byte, maxSessionKeySizeInBytes)
+	// The session key may follow. We just have to try and read to find
+	// out. If it exists then we limit it to maxSessionKeySizeInBytes.
+	n, err := readFull(r, encryptedKey)
+	if err != nil && err != io.ErrUnexpectedEOF {
+		return
+	}
+	err = nil
+	if n != 0 {
+		if n == maxSessionKeySizeInBytes {
+			return error.UnsupportedError("oversized encrypted session key")
+		}
+		ske.encryptedKey = encryptedKey[:n]
+	}
+
+	ske.Encrypted = true
+
+	return
+}
+
+// Decrypt attempts to decrypt an encrypted session key. If it returns nil,
+// ske.Key will contain the session key.
+func (ske *SymmetricKeyEncrypted) Decrypt(passphrase []byte) os.Error {
+	if !ske.Encrypted {
+		return nil
+	}
+
+	key := make([]byte, ske.CipherFunc.KeySize())
+	ske.s2k(key, passphrase)
+
+	if len(ske.encryptedKey) == 0 {
+		ske.Key = key
+	} else {
+		// the IV is all zeros
+		iv := make([]byte, ske.CipherFunc.blockSize())
+		c := cipher.NewCFBDecrypter(ske.CipherFunc.new(key), iv)
+		c.XORKeyStream(ske.encryptedKey, ske.encryptedKey)
+		ske.CipherFunc = CipherFunction(ske.encryptedKey[0])
+		if ske.CipherFunc.blockSize() == 0 {
+			return error.UnsupportedError("unknown cipher: " + strconv.Itoa(int(ske.CipherFunc)))
+		}
+		ske.CipherFunc = CipherFunction(ske.encryptedKey[0])
+		ske.Key = ske.encryptedKey[1:]
+		if len(ske.Key)%ske.CipherFunc.blockSize() != 0 {
+			ske.Key = nil
+			return error.StructuralError("length of decrypted key not a multiple of block size")
+		}
+	}
+
+	ske.Encrypted = false
+	return nil
+}
+
+// SerializeSymmetricKeyEncrypted serializes a symmetric key packet to w. The
+// packet contains a random session key, encrypted by a key derived from the
+// given passphrase. The session key is returned and must be passed to
+// SerializeSymmetricallyEncrypted.
+func SerializeSymmetricKeyEncrypted(w io.Writer, rand io.Reader, passphrase []byte, cipherFunc CipherFunction) (key []byte, err os.Error) {
+	keySize := cipherFunc.KeySize()
+	if keySize == 0 {
+		return nil, error.UnsupportedError("unknown cipher: " + strconv.Itoa(int(cipherFunc)))
+	}
+
+	s2kBuf := new(bytes.Buffer)
+	keyEncryptingKey := make([]byte, keySize)
+	// s2k.Serialize salts and stretches the passphrase, and writes the
+	// resulting key to keyEncryptingKey and the s2k descriptor to s2kBuf.
+	err = s2k.Serialize(s2kBuf, keyEncryptingKey, rand, passphrase)
+	if err != nil {
+		return
+	}
+	s2kBytes := s2kBuf.Bytes()
+
+	packetLength := 2 /* header */ + len(s2kBytes) + 1 /* cipher type */ + keySize
+	err = serializeHeader(w, packetTypeSymmetricKeyEncrypted, packetLength)
+	if err != nil {
+		return
+	}
+
+	var buf [2]byte
+	buf[0] = symmetricKeyEncryptedVersion
+	buf[1] = byte(cipherFunc)
+	_, err = w.Write(buf[:])
+	if err != nil {
+		return
+	}
+	_, err = w.Write(s2kBytes)
+	if err != nil {
+		return
+	}
+
+	sessionKey := make([]byte, keySize)
+	_, err = io.ReadFull(rand, sessionKey)
+	if err != nil {
+		return
+	}
+	iv := make([]byte, cipherFunc.blockSize())
+	c := cipher.NewCFBEncrypter(cipherFunc.new(keyEncryptingKey), iv)
+	encryptedCipherAndKey := make([]byte, keySize+1)
+	c.XORKeyStream(encryptedCipherAndKey, buf[1:])
+	c.XORKeyStream(encryptedCipherAndKey[1:], sessionKey)
+	_, err = w.Write(encryptedCipherAndKey)
+	if err != nil {
+		return
+	}
+
+	key = sessionKey
+	return
+}
diff --git a/src/pkg/crypto/openpgp/packet/symmetric_key_encrypted_test.go b/src/pkg/crypto/openpgp/packet/symmetric_key_encrypted_test.go
new file mode 100644
index 000000000..823ec400d
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/symmetric_key_encrypted_test.go
@@ -0,0 +1,101 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/hex"
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+func TestSymmetricKeyEncrypted(t *testing.T) {
+	buf := readerFromHex(symmetricallyEncryptedHex)
+	packet, err := Read(buf)
+	if err != nil {
+		t.Errorf("failed to read SymmetricKeyEncrypted: %s", err)
+		return
+	}
+	ske, ok := packet.(*SymmetricKeyEncrypted)
+	if !ok {
+		t.Error("didn't find SymmetricKeyEncrypted packet")
+		return
+	}
+	err = ske.Decrypt([]byte("password"))
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	packet, err = Read(buf)
+	if err != nil {
+		t.Errorf("failed to read SymmetricallyEncrypted: %s", err)
+		return
+	}
+	se, ok := packet.(*SymmetricallyEncrypted)
+	if !ok {
+		t.Error("didn't find SymmetricallyEncrypted packet")
+		return
+	}
+	r, err := se.Decrypt(ske.CipherFunc, ske.Key)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	contents, err := ioutil.ReadAll(r)
+	if err != nil && err != os.EOF {
+		t.Error(err)
+		return
+	}
+
+	expectedContents, _ := hex.DecodeString(symmetricallyEncryptedContentsHex)
+	if !bytes.Equal(expectedContents, contents) {
+		t.Errorf("bad contents got:%x want:%x", contents, expectedContents)
+	}
+}
+
+const symmetricallyEncryptedHex = "8c0d04030302371a0b38d884f02060c91cf97c9973b8e58e028e9501708ccfe618fb92afef7fa2d80ddadd93cf"
+const symmetricallyEncryptedContentsHex = "cb1062004d14c4df636f6e74656e74732e0a"
+
+func TestSerializeSymmetricKeyEncrypted(t *testing.T) {
+	buf := bytes.NewBuffer(nil)
+	passphrase := []byte("testing")
+	cipherFunc := CipherAES128
+
+	key, err := SerializeSymmetricKeyEncrypted(buf, rand.Reader, passphrase, cipherFunc)
+	if err != nil {
+		t.Errorf("failed to serialize: %s", err)
+		return
+	}
+
+	p, err := Read(buf)
+	if err != nil {
+		t.Errorf("failed to reparse: %s", err)
+		return
+	}
+	ske, ok := p.(*SymmetricKeyEncrypted)
+	if !ok {
+		t.Errorf("parsed a different packet type: %#v", p)
+		return
+	}
+
+	if !ske.Encrypted {
+		t.Errorf("SKE not encrypted but should be")
+	}
+	if ske.CipherFunc != cipherFunc {
+		t.Errorf("SKE cipher function is %d (expected %d)", ske.CipherFunc, cipherFunc)
+	}
+	err = ske.Decrypt(passphrase)
+	if err != nil {
+		t.Errorf("failed to decrypt reparsed SKE: %s", err)
+		return
+	}
+	if !bytes.Equal(key, ske.Key) {
+		t.Errorf("keys don't match after Decrpyt: %x (original) vs %x (parsed)", key, ske.Key)
+	}
+}
diff --git a/src/pkg/crypto/openpgp/packet/symmetrically_encrypted.go b/src/pkg/crypto/openpgp/packet/symmetrically_encrypted.go
new file mode 100644
index 000000000..e33c9f3a0
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/symmetrically_encrypted.go
@@ -0,0 +1,291 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"crypto/cipher"
+	"crypto/openpgp/error"
+	"crypto/rand"
+	"crypto/sha1"
+	"crypto/subtle"
+	"hash"
+	"io"
+	"os"
+	"strconv"
+)
+
+// SymmetricallyEncrypted represents a symmetrically encrypted byte string. The
+// encrypted contents will consist of more OpenPGP packets. See RFC 4880,
+// sections 5.7 and 5.13.
+type SymmetricallyEncrypted struct {
+	MDC      bool // true iff this is a type 18 packet and thus has an embedded MAC.
+	contents io.Reader
+	prefix   []byte
+}
+
+const symmetricallyEncryptedVersion = 1
+
+func (se *SymmetricallyEncrypted) parse(r io.Reader) os.Error {
+	if se.MDC {
+		// See RFC 4880, section 5.13.
+		var buf [1]byte
+		_, err := readFull(r, buf[:])
+		if err != nil {
+			return err
+		}
+		if buf[0] != symmetricallyEncryptedVersion {
+			return error.UnsupportedError("unknown SymmetricallyEncrypted version")
+		}
+	}
+	se.contents = r
+	return nil
+}
+
+// Decrypt returns a ReadCloser, from which the decrypted contents of the
+// packet can be read. An incorrect key can, with high probability, be detected
+// immediately and this will result in a KeyIncorrect error being returned.
+func (se *SymmetricallyEncrypted) Decrypt(c CipherFunction, key []byte) (io.ReadCloser, os.Error) {
+	keySize := c.KeySize()
+	if keySize == 0 {
+		return nil, error.UnsupportedError("unknown cipher: " + strconv.Itoa(int(c)))
+	}
+	if len(key) != keySize {
+		return nil, error.InvalidArgumentError("SymmetricallyEncrypted: incorrect key length")
+	}
+
+	if se.prefix == nil {
+		se.prefix = make([]byte, c.blockSize()+2)
+		_, err := readFull(se.contents, se.prefix)
+		if err != nil {
+			return nil, err
+		}
+	} else if len(se.prefix) != c.blockSize()+2 {
+		return nil, error.InvalidArgumentError("can't try ciphers with different block lengths")
+	}
+
+	ocfbResync := cipher.OCFBResync
+	if se.MDC {
+		// MDC packets use a different form of OCFB mode.
+		ocfbResync = cipher.OCFBNoResync
+	}
+
+	s := cipher.NewOCFBDecrypter(c.new(key), se.prefix, ocfbResync)
+	if s == nil {
+		return nil, error.KeyIncorrectError
+	}
+
+	plaintext := cipher.StreamReader{S: s, R: se.contents}
+
+	if se.MDC {
+		// MDC packets have an embedded hash that we need to check.
+		h := sha1.New()
+		h.Write(se.prefix)
+		return &seMDCReader{in: plaintext, h: h}, nil
+	}
+
+	// Otherwise, we just need to wrap plaintext so that it's a valid ReadCloser.
+	return seReader{plaintext}, nil
+}
+
+// seReader wraps an io.Reader with a no-op Close method.
+type seReader struct {
+	in io.Reader
+}
+
+func (ser seReader) Read(buf []byte) (int, os.Error) {
+	return ser.in.Read(buf)
+}
+
+func (ser seReader) Close() os.Error {
+	return nil
+}
+
+const mdcTrailerSize = 1 /* tag byte */ + 1 /* length byte */ + sha1.Size
+
+// An seMDCReader wraps an io.Reader, maintains a running hash and keeps hold
+// of the most recent 22 bytes (mdcTrailerSize). Upon EOF, those bytes form an
+// MDC packet containing a hash of the previous contents which is checked
+// against the running hash. See RFC 4880, section 5.13.
+type seMDCReader struct {
+	in          io.Reader
+	h           hash.Hash
+	trailer     [mdcTrailerSize]byte
+	scratch     [mdcTrailerSize]byte
+	trailerUsed int
+	error       bool
+	eof         bool
+}
+
+func (ser *seMDCReader) Read(buf []byte) (n int, err os.Error) {
+	if ser.error {
+		err = io.ErrUnexpectedEOF
+		return
+	}
+	if ser.eof {
+		err = os.EOF
+		return
+	}
+
+	// If we haven't yet filled the trailer buffer then we must do that
+	// first.
+	for ser.trailerUsed < mdcTrailerSize {
+		n, err = ser.in.Read(ser.trailer[ser.trailerUsed:])
+		ser.trailerUsed += n
+		if err == os.EOF {
+			if ser.trailerUsed != mdcTrailerSize {
+				n = 0
+				err = io.ErrUnexpectedEOF
+				ser.error = true
+				return
+			}
+			ser.eof = true
+			n = 0
+			return
+		}
+
+		if err != nil {
+			n = 0
+			return
+		}
+	}
+
+	// If it's a short read then we read into a temporary buffer and shift
+	// the data into the caller's buffer.
+	if len(buf) <= mdcTrailerSize {
+		n, err = readFull(ser.in, ser.scratch[:len(buf)])
+		copy(buf, ser.trailer[:n])
+		ser.h.Write(buf[:n])
+		copy(ser.trailer[:], ser.trailer[n:])
+		copy(ser.trailer[mdcTrailerSize-n:], ser.scratch[:])
+		if n < len(buf) {
+			ser.eof = true
+			err = os.EOF
+		}
+		return
+	}
+
+	n, err = ser.in.Read(buf[mdcTrailerSize:])
+	copy(buf, ser.trailer[:])
+	ser.h.Write(buf[:n])
+	copy(ser.trailer[:], buf[n:])
+
+	if err == os.EOF {
+		ser.eof = true
+	}
+	return
+}
+
+// This is a new-format packet tag byte for a type 19 (MDC) packet.
+const mdcPacketTagByte = byte(0x80) | 0x40 | 19
+
+func (ser *seMDCReader) Close() os.Error {
+	if ser.error {
+		return error.SignatureError("error during reading")
+	}
+
+	for !ser.eof {
+		// We haven't seen EOF so we need to read to the end
+		var buf [1024]byte
+		_, err := ser.Read(buf[:])
+		if err == os.EOF {
+			break
+		}
+		if err != nil {
+			return error.SignatureError("error during reading")
+		}
+	}
+
+	if ser.trailer[0] != mdcPacketTagByte || ser.trailer[1] != sha1.Size {
+		return error.SignatureError("MDC packet not found")
+	}
+	ser.h.Write(ser.trailer[:2])
+
+	final := ser.h.Sum()
+	if subtle.ConstantTimeCompare(final, ser.trailer[2:]) != 1 {
+		return error.SignatureError("hash mismatch")
+	}
+	return nil
+}
+
+// An seMDCWriter writes through to an io.WriteCloser while maintains a running
+// hash of the data written. On close, it emits an MDC packet containing the
+// running hash.
+type seMDCWriter struct {
+	w io.WriteCloser
+	h hash.Hash
+}
+
+func (w *seMDCWriter) Write(buf []byte) (n int, err os.Error) {
+	w.h.Write(buf)
+	return w.w.Write(buf)
+}
+
+func (w *seMDCWriter) Close() (err os.Error) {
+	var buf [mdcTrailerSize]byte
+
+	buf[0] = mdcPacketTagByte
+	buf[1] = sha1.Size
+	w.h.Write(buf[:2])
+	digest := w.h.Sum()
+	copy(buf[2:], digest)
+
+	_, err = w.w.Write(buf[:])
+	if err != nil {
+		return
+	}
+	return w.w.Close()
+}
+
+// noOpCloser is like an ioutil.NopCloser, but for an io.Writer.
+type noOpCloser struct {
+	w io.Writer
+}
+
+func (c noOpCloser) Write(data []byte) (n int, err os.Error) {
+	return c.w.Write(data)
+}
+
+func (c noOpCloser) Close() os.Error {
+	return nil
+}
+
+// SerializeSymmetricallyEncrypted serializes a symmetrically encrypted packet
+// to w and returns a WriteCloser to which the to-be-encrypted packets can be
+// written.
+func SerializeSymmetricallyEncrypted(w io.Writer, c CipherFunction, key []byte) (contents io.WriteCloser, err os.Error) {
+	if c.KeySize() != len(key) {
+		return nil, error.InvalidArgumentError("SymmetricallyEncrypted.Serialize: bad key length")
+	}
+	writeCloser := noOpCloser{w}
+	ciphertext, err := serializeStreamHeader(writeCloser, packetTypeSymmetricallyEncryptedMDC)
+	if err != nil {
+		return
+	}
+
+	_, err = ciphertext.Write([]byte{symmetricallyEncryptedVersion})
+	if err != nil {
+		return
+	}
+
+	block := c.new(key)
+	blockSize := block.BlockSize()
+	iv := make([]byte, blockSize)
+	_, err = rand.Reader.Read(iv)
+	if err != nil {
+		return
+	}
+	s, prefix := cipher.NewOCFBEncrypter(block, iv, cipher.OCFBNoResync)
+	_, err = ciphertext.Write(prefix)
+	if err != nil {
+		return
+	}
+	plaintext := cipher.StreamWriter{S: s, W: ciphertext}
+
+	h := sha1.New()
+	h.Write(iv)
+	h.Write(iv[blockSize-2:])
+	contents = &seMDCWriter{w: plaintext, h: h}
+	return
+}
diff --git a/src/pkg/crypto/openpgp/packet/symmetrically_encrypted_test.go b/src/pkg/crypto/openpgp/packet/symmetrically_encrypted_test.go
new file mode 100644
index 000000000..1054fc2f9
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/symmetrically_encrypted_test.go
@@ -0,0 +1,124 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"bytes"
+	"crypto/openpgp/error"
+	"crypto/sha1"
+	"encoding/hex"
+	"io"
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+// TestReader wraps a []byte and returns reads of a specific length.
+type testReader struct {
+	data   []byte
+	stride int
+}
+
+func (t *testReader) Read(buf []byte) (n int, err os.Error) {
+	n = t.stride
+	if n > len(t.data) {
+		n = len(t.data)
+	}
+	if n > len(buf) {
+		n = len(buf)
+	}
+	copy(buf, t.data)
+	t.data = t.data[n:]
+	if len(t.data) == 0 {
+		err = os.EOF
+	}
+	return
+}
+
+func testMDCReader(t *testing.T) {
+	mdcPlaintext, _ := hex.DecodeString(mdcPlaintextHex)
+
+	for stride := 1; stride < len(mdcPlaintext)/2; stride++ {
+		r := &testReader{data: mdcPlaintext, stride: stride}
+		mdcReader := &seMDCReader{in: r, h: sha1.New()}
+		body, err := ioutil.ReadAll(mdcReader)
+		if err != nil {
+			t.Errorf("stride: %d, error: %s", stride, err)
+			continue
+		}
+		if !bytes.Equal(body, mdcPlaintext[:len(mdcPlaintext)-22]) {
+			t.Errorf("stride: %d: bad contents %x", stride, body)
+			continue
+		}
+
+		err = mdcReader.Close()
+		if err != nil {
+			t.Errorf("stride: %d, error on Close: %s", stride, err)
+		}
+	}
+
+	mdcPlaintext[15] ^= 80
+
+	r := &testReader{data: mdcPlaintext, stride: 2}
+	mdcReader := &seMDCReader{in: r, h: sha1.New()}
+	_, err := ioutil.ReadAll(mdcReader)
+	if err != nil {
+		t.Errorf("corruption test, error: %s", err)
+		return
+	}
+	err = mdcReader.Close()
+	if err == nil {
+		t.Error("corruption: no error")
+	} else if _, ok := err.(*error.SignatureError); !ok {
+		t.Errorf("corruption: expected SignatureError, got: %s", err)
+	}
+}
+
+const mdcPlaintextHex = "a302789c3b2d93c4e0eb9aba22283539b3203335af44a134afb800c849cb4c4de10200aff40b45d31432c80cb384299a0655966d6939dfdeed1dddf980"
+
+func TestSerialize(t *testing.T) {
+	buf := bytes.NewBuffer(nil)
+	c := CipherAES128
+	key := make([]byte, c.KeySize())
+
+	w, err := SerializeSymmetricallyEncrypted(buf, c, key)
+	if err != nil {
+		t.Errorf("error from SerializeSymmetricallyEncrypted: %s", err)
+		return
+	}
+
+	contents := []byte("hello world\n")
+
+	w.Write(contents)
+	w.Close()
+
+	p, err := Read(buf)
+	if err != nil {
+		t.Errorf("error from Read: %s", err)
+		return
+	}
+
+	se, ok := p.(*SymmetricallyEncrypted)
+	if !ok {
+		t.Errorf("didn't read a *SymmetricallyEncrypted")
+		return
+	}
+
+	r, err := se.Decrypt(c, key)
+	if err != nil {
+		t.Errorf("error from Decrypt: %s", err)
+		return
+	}
+
+	contentsCopy := bytes.NewBuffer(nil)
+	_, err = io.Copy(contentsCopy, r)
+	if err != nil {
+		t.Errorf("error from io.Copy: %s", err)
+		return
+	}
+	if !bytes.Equal(contentsCopy.Bytes(), contents) {
+		t.Errorf("contents not equal got: %x want: %x", contentsCopy.Bytes(), contents)
+	}
+}
diff --git a/src/pkg/crypto/openpgp/packet/userid.go b/src/pkg/crypto/openpgp/packet/userid.go
new file mode 100644
index 000000000..0580ba3ed
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/userid.go
@@ -0,0 +1,161 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"io"
+	"io/ioutil"
+	"os"
+	"strings"
+)
+
+// UserId contains text that is intended to represent the name and email
+// address of the key holder. See RFC 4880, section 5.11. By convention, this
+// takes the form "Full Name (Comment) <email@example.com>"
+type UserId struct {
+	Id string // By convention, this takes the form "Full Name (Comment) <email@example.com>" which is split out in the fields below.
+
+	Name, Comment, Email string
+}
+
+func hasInvalidCharacters(s string) bool {
+	for _, c := range s {
+		switch c {
+		case '(', ')', '<', '>', 0:
+			return true
+		}
+	}
+	return false
+}
+
+// NewUserId returns a UserId or nil if any of the arguments contain invalid
+// characters. The invalid characters are '\x00', '(', ')', '<' and '>'
+func NewUserId(name, comment, email string) *UserId {
+	// RFC 4880 doesn't deal with the structure of userid strings; the
+	// name, comment and email form is just a convention. However, there's
+	// no convention about escaping the metacharacters and GPG just refuses
+	// to create user ids where, say, the name contains a '('. We mirror
+	// this behaviour.
+
+	if hasInvalidCharacters(name) || hasInvalidCharacters(comment) || hasInvalidCharacters(email) {
+		return nil
+	}
+
+	uid := new(UserId)
+	uid.Name, uid.Comment, uid.Email = name, comment, email
+	uid.Id = name
+	if len(comment) > 0 {
+		if len(uid.Id) > 0 {
+			uid.Id += " "
+		}
+		uid.Id += "("
+		uid.Id += comment
+		uid.Id += ")"
+	}
+	if len(email) > 0 {
+		if len(uid.Id) > 0 {
+			uid.Id += " "
+		}
+		uid.Id += "<"
+		uid.Id += email
+		uid.Id += ">"
+	}
+	return uid
+}
+
+func (uid *UserId) parse(r io.Reader) (err os.Error) {
+	// RFC 4880, section 5.11
+	b, err := ioutil.ReadAll(r)
+	if err != nil {
+		return
+	}
+	uid.Id = string(b)
+	uid.Name, uid.Comment, uid.Email = parseUserId(uid.Id)
+	return
+}
+
+// Serialize marshals uid to w in the form of an OpenPGP packet, including
+// header.
+func (uid *UserId) Serialize(w io.Writer) os.Error {
+	err := serializeHeader(w, packetTypeUserId, len(uid.Id))
+	if err != nil {
+		return err
+	}
+	_, err = w.Write([]byte(uid.Id))
+	return err
+}
+
+// parseUserId extracts the name, comment and email from a user id string that
+// is formatted as "Full Name (Comment) <email@example.com>".
+func parseUserId(id string) (name, comment, email string) {
+	var n, c, e struct {
+		start, end int
+	}
+	var state int
+
+	for offset, rune := range id {
+		switch state {
+		case 0:
+			// Entering name
+			n.start = offset
+			state = 1
+			fallthrough
+		case 1:
+			// In name
+			if rune == '(' {
+				state = 2
+				n.end = offset
+			} else if rune == '<' {
+				state = 5
+				n.end = offset
+			}
+		case 2:
+			// Entering comment
+			c.start = offset
+			state = 3
+			fallthrough
+		case 3:
+			// In comment
+			if rune == ')' {
+				state = 4
+				c.end = offset
+			}
+		case 4:
+			// Between comment and email
+			if rune == '<' {
+				state = 5
+			}
+		case 5:
+			// Entering email
+			e.start = offset
+			state = 6
+			fallthrough
+		case 6:
+			// In email
+			if rune == '>' {
+				state = 7
+				e.end = offset
+			}
+		default:
+			// After email
+		}
+	}
+	switch state {
+	case 1:
+		// ended in the name
+		n.end = len(id)
+	case 3:
+		// ended in comment
+		c.end = len(id)
+	case 6:
+		// ended in email
+		e.end = len(id)
+	}
+
+	name = strings.TrimSpace(id[n.start:n.end])
+	comment = strings.TrimSpace(id[c.start:c.end])
+	email = strings.TrimSpace(id[e.start:e.end])
+	return
+}
diff --git a/src/pkg/crypto/openpgp/packet/userid_test.go b/src/pkg/crypto/openpgp/packet/userid_test.go
new file mode 100644
index 000000000..296819389
--- /dev/null
+++ b/src/pkg/crypto/openpgp/packet/userid_test.go
@@ -0,0 +1,87 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"testing"
+)
+
+var userIdTests = []struct {
+	id                   string
+	name, comment, email string
+}{
+	{"", "", "", ""},
+	{"John Smith", "John Smith", "", ""},
+	{"John Smith ()", "John Smith", "", ""},
+	{"John Smith () <>", "John Smith", "", ""},
+	{"(comment", "", "comment", ""},
+	{"(comment)", "", "comment", ""},
+	{"<email", "", "", "email"},
+	{"<email>   sdfk", "", "", "email"},
+	{"  John Smith  (  Comment ) asdkflj < email > lksdfj", "John Smith", "Comment", "email"},
+	{"  John Smith  < email > lksdfj", "John Smith", "", "email"},
+	{"(<foo", "", "<foo", ""},
+	{"René Descartes (العربي)", "René Descartes", "العربي", ""},
+}
+
+func TestParseUserId(t *testing.T) {
+	for i, test := range userIdTests {
+		name, comment, email := parseUserId(test.id)
+		if name != test.name {
+			t.Errorf("%d: name mismatch got:%s want:%s", i, name, test.name)
+		}
+		if comment != test.comment {
+			t.Errorf("%d: comment mismatch got:%s want:%s", i, comment, test.comment)
+		}
+		if email != test.email {
+			t.Errorf("%d: email mismatch got:%s want:%s", i, email, test.email)
+		}
+	}
+}
+
+var newUserIdTests = []struct {
+	name, comment, email, id string
+}{
+	{"foo", "", "", "foo"},
+	{"", "bar", "", "(bar)"},
+	{"", "", "baz", "<baz>"},
+	{"foo", "bar", "", "foo (bar)"},
+	{"foo", "", "baz", "foo <baz>"},
+	{"", "bar", "baz", "(bar) <baz>"},
+	{"foo", "bar", "baz", "foo (bar) <baz>"},
+}
+
+func TestNewUserId(t *testing.T) {
+	for i, test := range newUserIdTests {
+		uid := NewUserId(test.name, test.comment, test.email)
+		if uid == nil {
+			t.Errorf("#%d: returned nil", i)
+			continue
+		}
+		if uid.Id != test.id {
+			t.Errorf("#%d: got '%s', want '%s'", i, uid.Id, test.id)
+		}
+	}
+}
+
+var invalidNewUserIdTests = []struct {
+	name, comment, email string
+}{
+	{"foo(", "", ""},
+	{"foo<", "", ""},
+	{"", "bar)", ""},
+	{"", "bar<", ""},
+	{"", "", "baz>"},
+	{"", "", "baz)"},
+	{"", "", "baz\x00"},
+}
+
+func TestNewUserIdWithInvalidInput(t *testing.T) {
+	for i, test := range invalidNewUserIdTests {
+		if uid := NewUserId(test.name, test.comment, test.email); uid != nil {
+			t.Errorf("#%d: returned non-nil value: %#v", i, uid)
+		}
+	}
+}