Imported Upstream version 1.4upstream/1.4

18 files changed, 1976 insertions, 0 deletions

diff --git a/src/crypto/cipher/benchmark_test.go b/src/crypto/cipher/benchmark_test.go
new file mode 100644
index 000000000..027b24851
--- /dev/null
+++ b/src/crypto/cipher/benchmark_test.go
@@ -0,0 +1,139 @@
+// Copyright 2013 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 cipher_test
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"testing"
+)
+
+func BenchmarkAESGCMSeal1K(b *testing.B) {
+	buf := make([]byte, 1024)
+	b.SetBytes(int64(len(buf)))
+
+	var key [16]byte
+	var nonce [12]byte
+	aes, _ := aes.NewCipher(key[:])
+	aesgcm, _ := cipher.NewGCM(aes)
+	var out []byte
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		out = aesgcm.Seal(out[:0], nonce[:], buf, nonce[:])
+	}
+}
+
+func BenchmarkAESGCMOpen1K(b *testing.B) {
+	buf := make([]byte, 1024)
+	b.SetBytes(int64(len(buf)))
+
+	var key [16]byte
+	var nonce [12]byte
+	aes, _ := aes.NewCipher(key[:])
+	aesgcm, _ := cipher.NewGCM(aes)
+	var out []byte
+	out = aesgcm.Seal(out[:0], nonce[:], buf, nonce[:])
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, err := aesgcm.Open(buf[:0], nonce[:], out, nonce[:])
+		if err != nil {
+			b.Errorf("Open: %v", err)
+		}
+	}
+}
+
+// If we test exactly 1K blocks, we would generate exact multiples of
+// the cipher's block size, and the cipher stream fragments would
+// always be wordsize aligned, whereas non-aligned is a more typical
+// use-case.
+const almost1K = 1024 - 5
+
+func BenchmarkAESCFBEncrypt1K(b *testing.B) {
+	buf := make([]byte, almost1K)
+	b.SetBytes(int64(len(buf)))
+
+	var key [16]byte
+	var iv [16]byte
+	aes, _ := aes.NewCipher(key[:])
+	ctr := cipher.NewCFBEncrypter(aes, iv[:])
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		ctr.XORKeyStream(buf, buf)
+	}
+}
+
+func BenchmarkAESCFBDecrypt1K(b *testing.B) {
+	buf := make([]byte, almost1K)
+	b.SetBytes(int64(len(buf)))
+
+	var key [16]byte
+	var iv [16]byte
+	aes, _ := aes.NewCipher(key[:])
+	ctr := cipher.NewCFBDecrypter(aes, iv[:])
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		ctr.XORKeyStream(buf, buf)
+	}
+}
+
+func BenchmarkAESOFB1K(b *testing.B) {
+	buf := make([]byte, almost1K)
+	b.SetBytes(int64(len(buf)))
+
+	var key [16]byte
+	var iv [16]byte
+	aes, _ := aes.NewCipher(key[:])
+	ctr := cipher.NewOFB(aes, iv[:])
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		ctr.XORKeyStream(buf, buf)
+	}
+}
+
+func BenchmarkAESCTR1K(b *testing.B) {
+	buf := make([]byte, almost1K)
+	b.SetBytes(int64(len(buf)))
+
+	var key [16]byte
+	var iv [16]byte
+	aes, _ := aes.NewCipher(key[:])
+	ctr := cipher.NewCTR(aes, iv[:])
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		ctr.XORKeyStream(buf, buf)
+	}
+}
+
+func BenchmarkAESCBCEncrypt1K(b *testing.B) {
+	buf := make([]byte, 1024)
+	b.SetBytes(int64(len(buf)))
+
+	var key [16]byte
+	var iv [16]byte
+	aes, _ := aes.NewCipher(key[:])
+	cbc := cipher.NewCBCEncrypter(aes, iv[:])
+	for i := 0; i < b.N; i++ {
+		cbc.CryptBlocks(buf, buf)
+	}
+}
+
+func BenchmarkAESCBCDecrypt1K(b *testing.B) {
+	buf := make([]byte, 1024)
+	b.SetBytes(int64(len(buf)))
+
+	var key [16]byte
+	var iv [16]byte
+	aes, _ := aes.NewCipher(key[:])
+	cbc := cipher.NewCBCDecrypter(aes, iv[:])
+	for i := 0; i < b.N; i++ {
+		cbc.CryptBlocks(buf, buf)
+	}
+}
diff --git a/src/crypto/cipher/cbc.go b/src/crypto/cipher/cbc.go
new file mode 100644
index 000000000..241e122ee
--- /dev/null
+++ b/src/crypto/cipher/cbc.go
@@ -0,0 +1,133 @@
+// Copyright 2009 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.
+
+// Cipher block chaining (CBC) mode.
+
+// CBC provides confidentiality by xoring (chaining) each plaintext block
+// with the previous ciphertext block before applying the block cipher.
+
+// See NIST SP 800-38A, pp 10-11
+
+package cipher
+
+type cbc struct {
+	b         Block
+	blockSize int
+	iv        []byte
+	tmp       []byte
+}
+
+func newCBC(b Block, iv []byte) *cbc {
+	return &cbc{
+		b:         b,
+		blockSize: b.BlockSize(),
+		iv:        dup(iv),
+		tmp:       make([]byte, b.BlockSize()),
+	}
+}
+
+type cbcEncrypter cbc
+
+// NewCBCEncrypter returns a BlockMode which encrypts in cipher block chaining
+// mode, using the given Block. The length of iv must be the same as the
+// Block's block size.
+func NewCBCEncrypter(b Block, iv []byte) BlockMode {
+	if len(iv) != b.BlockSize() {
+		panic("cipher.NewCBCEncrypter: IV length must equal block size")
+	}
+	return (*cbcEncrypter)(newCBC(b, iv))
+}
+
+func (x *cbcEncrypter) BlockSize() int { return x.blockSize }
+
+func (x *cbcEncrypter) CryptBlocks(dst, src []byte) {
+	if len(src)%x.blockSize != 0 {
+		panic("crypto/cipher: input not full blocks")
+	}
+	if len(dst) < len(src) {
+		panic("crypto/cipher: output smaller than input")
+	}
+
+	iv := x.iv
+
+	for len(src) > 0 {
+		// Write the xor to dst, then encrypt in place.
+		xorBytes(dst[:x.blockSize], src[:x.blockSize], iv)
+		x.b.Encrypt(dst[:x.blockSize], dst[:x.blockSize])
+
+		// Move to the next block with this block as the next iv.
+		iv = dst[:x.blockSize]
+		src = src[x.blockSize:]
+		dst = dst[x.blockSize:]
+	}
+
+	// Save the iv for the next CryptBlocks call.
+	copy(x.iv, iv)
+}
+
+func (x *cbcEncrypter) SetIV(iv []byte) {
+	if len(iv) != len(x.iv) {
+		panic("cipher: incorrect length IV")
+	}
+	copy(x.iv, iv)
+}
+
+type cbcDecrypter cbc
+
+// NewCBCDecrypter returns a BlockMode which decrypts in cipher block chaining
+// mode, using the given Block. The length of iv must be the same as the
+// Block's block size and must match the iv used to encrypt the data.
+func NewCBCDecrypter(b Block, iv []byte) BlockMode {
+	if len(iv) != b.BlockSize() {
+		panic("cipher.NewCBCDecrypter: IV length must equal block size")
+	}
+	return (*cbcDecrypter)(newCBC(b, iv))
+}
+
+func (x *cbcDecrypter) BlockSize() int { return x.blockSize }
+
+func (x *cbcDecrypter) CryptBlocks(dst, src []byte) {
+	if len(src)%x.blockSize != 0 {
+		panic("crypto/cipher: input not full blocks")
+	}
+	if len(dst) < len(src) {
+		panic("crypto/cipher: output smaller than input")
+	}
+	if len(src) == 0 {
+		return
+	}
+
+	// For each block, we need to xor the decrypted data with the previous block's ciphertext (the iv).
+	// To avoid making a copy each time, we loop over the blocks BACKWARDS.
+	end := len(src)
+	start := end - x.blockSize
+	prev := start - x.blockSize
+
+	// Copy the last block of ciphertext in preparation as the new iv.
+	copy(x.tmp, src[start:end])
+
+	// Loop over all but the first block.
+	for start > 0 {
+		x.b.Decrypt(dst[start:end], src[start:end])
+		xorBytes(dst[start:end], dst[start:end], src[prev:start])
+
+		end = start
+		start = prev
+		prev -= x.blockSize
+	}
+
+	// The first block is special because it uses the saved iv.
+	x.b.Decrypt(dst[start:end], src[start:end])
+	xorBytes(dst[start:end], dst[start:end], x.iv)
+
+	// Set the new iv to the first block we copied earlier.
+	x.iv, x.tmp = x.tmp, x.iv
+}
+
+func (x *cbcDecrypter) SetIV(iv []byte) {
+	if len(iv) != len(x.iv) {
+		panic("cipher: incorrect length IV")
+	}
+	copy(x.iv, iv)
+}
diff --git a/src/crypto/cipher/cbc_aes_test.go b/src/crypto/cipher/cbc_aes_test.go
new file mode 100644
index 000000000..bf9e7ad70
--- /dev/null
+++ b/src/crypto/cipher/cbc_aes_test.go
@@ -0,0 +1,104 @@
+// Copyright 2009 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.
+
+// CBC AES test vectors.
+
+// See U.S. National Institute of Standards and Technology (NIST)
+// Special Publication 800-38A, ``Recommendation for Block Cipher
+// Modes of Operation,'' 2001 Edition, pp. 24-29.
+
+package cipher_test
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"testing"
+)
+
+var cbcAESTests = []struct {
+	name string
+	key  []byte
+	iv   []byte
+	in   []byte
+	out  []byte
+}{
+	// NIST SP 800-38A pp 27-29
+	{
+		"CBC-AES128",
+		commonKey128,
+		commonIV,
+		commonInput,
+		[]byte{
+			0x76, 0x49, 0xab, 0xac, 0x81, 0x19, 0xb2, 0x46, 0xce, 0xe9, 0x8e, 0x9b, 0x12, 0xe9, 0x19, 0x7d,
+			0x50, 0x86, 0xcb, 0x9b, 0x50, 0x72, 0x19, 0xee, 0x95, 0xdb, 0x11, 0x3a, 0x91, 0x76, 0x78, 0xb2,
+			0x73, 0xbe, 0xd6, 0xb8, 0xe3, 0xc1, 0x74, 0x3b, 0x71, 0x16, 0xe6, 0x9e, 0x22, 0x22, 0x95, 0x16,
+			0x3f, 0xf1, 0xca, 0xa1, 0x68, 0x1f, 0xac, 0x09, 0x12, 0x0e, 0xca, 0x30, 0x75, 0x86, 0xe1, 0xa7,
+		},
+	},
+	{
+		"CBC-AES192",
+		commonKey192,
+		commonIV,
+		commonInput,
+		[]byte{
+			0x4f, 0x02, 0x1d, 0xb2, 0x43, 0xbc, 0x63, 0x3d, 0x71, 0x78, 0x18, 0x3a, 0x9f, 0xa0, 0x71, 0xe8,
+			0xb4, 0xd9, 0xad, 0xa9, 0xad, 0x7d, 0xed, 0xf4, 0xe5, 0xe7, 0x38, 0x76, 0x3f, 0x69, 0x14, 0x5a,
+			0x57, 0x1b, 0x24, 0x20, 0x12, 0xfb, 0x7a, 0xe0, 0x7f, 0xa9, 0xba, 0xac, 0x3d, 0xf1, 0x02, 0xe0,
+			0x08, 0xb0, 0xe2, 0x79, 0x88, 0x59, 0x88, 0x81, 0xd9, 0x20, 0xa9, 0xe6, 0x4f, 0x56, 0x15, 0xcd,
+		},
+	},
+	{
+		"CBC-AES256",
+		commonKey256,
+		commonIV,
+		commonInput,
+		[]byte{
+			0xf5, 0x8c, 0x4c, 0x04, 0xd6, 0xe5, 0xf1, 0xba, 0x77, 0x9e, 0xab, 0xfb, 0x5f, 0x7b, 0xfb, 0xd6,
+			0x9c, 0xfc, 0x4e, 0x96, 0x7e, 0xdb, 0x80, 0x8d, 0x67, 0x9f, 0x77, 0x7b, 0xc6, 0x70, 0x2c, 0x7d,
+			0x39, 0xf2, 0x33, 0x69, 0xa9, 0xd9, 0xba, 0xcf, 0xa5, 0x30, 0xe2, 0x63, 0x04, 0x23, 0x14, 0x61,
+			0xb2, 0xeb, 0x05, 0xe2, 0xc3, 0x9b, 0xe9, 0xfc, 0xda, 0x6c, 0x19, 0x07, 0x8c, 0x6a, 0x9d, 0x1b,
+		},
+	},
+}
+
+func TestCBCEncrypterAES(t *testing.T) {
+	for _, test := range cbcAESTests {
+		c, err := aes.NewCipher(test.key)
+		if err != nil {
+			t.Errorf("%s: NewCipher(%d bytes) = %s", test.name, len(test.key), err)
+			continue
+		}
+
+		encrypter := cipher.NewCBCEncrypter(c, test.iv)
+
+		data := make([]byte, len(test.in))
+		copy(data, test.in)
+
+		encrypter.CryptBlocks(data, data)
+		if !bytes.Equal(test.out, data) {
+			t.Errorf("%s: CBCEncrypter\nhave %x\nwant %x", test.name, data, test.out)
+		}
+	}
+}
+
+func TestCBCDecrypterAES(t *testing.T) {
+	for _, test := range cbcAESTests {
+		c, err := aes.NewCipher(test.key)
+		if err != nil {
+			t.Errorf("%s: NewCipher(%d bytes) = %s", test.name, len(test.key), err)
+			continue
+		}
+
+		decrypter := cipher.NewCBCDecrypter(c, test.iv)
+
+		data := make([]byte, len(test.out))
+		copy(data, test.out)
+
+		decrypter.CryptBlocks(data, data)
+		if !bytes.Equal(test.in, data) {
+			t.Errorf("%s: CBCDecrypter\nhave %x\nwant %x", test.name, data, test.in)
+		}
+	}
+}
diff --git a/src/crypto/cipher/cfb.go b/src/crypto/cipher/cfb.go
new file mode 100644
index 000000000..9b4eebf5b
--- /dev/null
+++ b/src/crypto/cipher/cfb.go
@@ -0,0 +1,72 @@
+// Copyright 2010 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.
+
+// CFB (Cipher Feedback) Mode.
+
+package cipher
+
+type cfb struct {
+	b       Block
+	next    []byte
+	out     []byte
+	outUsed int
+
+	decrypt bool
+}
+
+func (x *cfb) XORKeyStream(dst, src []byte) {
+	for len(src) > 0 {
+		if x.outUsed == len(x.out) {
+			x.b.Encrypt(x.out, x.next)
+			x.outUsed = 0
+		}
+
+		if x.decrypt {
+			// We can precompute a larger segment of the
+			// keystream on decryption. This will allow
+			// larger batches for xor, and we should be
+			// able to match CTR/OFB performance.
+			copy(x.next[x.outUsed:], src)
+		}
+		n := xorBytes(dst, src, x.out[x.outUsed:])
+		if !x.decrypt {
+			copy(x.next[x.outUsed:], dst)
+		}
+		dst = dst[n:]
+		src = src[n:]
+		x.outUsed += n
+	}
+}
+
+// NewCFBEncrypter returns a Stream which encrypts with cipher feedback mode,
+// using the given Block. The iv must be the same length as the Block's block
+// size.
+func NewCFBEncrypter(block Block, iv []byte) Stream {
+	return newCFB(block, iv, false)
+}
+
+// NewCFBDecrypter returns a Stream which decrypts with cipher feedback mode,
+// using the given Block. The iv must be the same length as the Block's block
+// size.
+func NewCFBDecrypter(block Block, iv []byte) Stream {
+	return newCFB(block, iv, true)
+}
+
+func newCFB(block Block, iv []byte, decrypt bool) Stream {
+	blockSize := block.BlockSize()
+	if len(iv) != blockSize {
+		// stack trace will indicate whether it was de or encryption
+		panic("cipher.newCFB: IV length must equal block size")
+	}
+	x := &cfb{
+		b:       block,
+		out:     make([]byte, blockSize),
+		next:    make([]byte, blockSize),
+		outUsed: blockSize,
+		decrypt: decrypt,
+	}
+	copy(x.next, iv)
+
+	return x
+}
diff --git a/src/crypto/cipher/cfb_test.go b/src/crypto/cipher/cfb_test.go
new file mode 100644
index 000000000..9b544bb21
--- /dev/null
+++ b/src/crypto/cipher/cfb_test.go
@@ -0,0 +1,113 @@
+// Copyright 2010 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 cipher_test
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/hex"
+	"testing"
+)
+
+// cfbTests contains the test vectors from
+// http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf, section
+// F.3.13.
+var cfbTests = []struct {
+	key, iv, plaintext, ciphertext string
+}{
+	{
+		"2b7e151628aed2a6abf7158809cf4f3c",
+		"000102030405060708090a0b0c0d0e0f",
+		"6bc1bee22e409f96e93d7e117393172a",
+		"3b3fd92eb72dad20333449f8e83cfb4a",
+	},
+	{
+		"2b7e151628aed2a6abf7158809cf4f3c",
+		"3B3FD92EB72DAD20333449F8E83CFB4A",
+		"ae2d8a571e03ac9c9eb76fac45af8e51",
+		"c8a64537a0b3a93fcde3cdad9f1ce58b",
+	},
+	{
+		"2b7e151628aed2a6abf7158809cf4f3c",
+		"C8A64537A0B3A93FCDE3CDAD9F1CE58B",
+		"30c81c46a35ce411e5fbc1191a0a52ef",
+		"26751f67a3cbb140b1808cf187a4f4df",
+	},
+	{
+		"2b7e151628aed2a6abf7158809cf4f3c",
+		"26751F67A3CBB140B1808CF187A4F4DF",
+		"f69f2445df4f9b17ad2b417be66c3710",
+		"c04b05357c5d1c0eeac4c66f9ff7f2e6",
+	},
+}
+
+func TestCFBVectors(t *testing.T) {
+	for i, test := range cfbTests {
+		key, err := hex.DecodeString(test.key)
+		if err != nil {
+			t.Fatal(err)
+		}
+		iv, err := hex.DecodeString(test.iv)
+		if err != nil {
+			t.Fatal(err)
+		}
+		plaintext, err := hex.DecodeString(test.plaintext)
+		if err != nil {
+			t.Fatal(err)
+		}
+		expected, err := hex.DecodeString(test.ciphertext)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		block, err := aes.NewCipher(key)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		ciphertext := make([]byte, len(plaintext))
+		cfb := cipher.NewCFBEncrypter(block, iv)
+		cfb.XORKeyStream(ciphertext, plaintext)
+
+		if !bytes.Equal(ciphertext, expected) {
+			t.Errorf("#%d: wrong output: got %x, expected %x", i, ciphertext, expected)
+		}
+
+		cfbdec := cipher.NewCFBDecrypter(block, iv)
+		plaintextCopy := make([]byte, len(ciphertext))
+		cfbdec.XORKeyStream(plaintextCopy, ciphertext)
+
+		if !bytes.Equal(plaintextCopy, plaintextCopy) {
+			t.Errorf("#%d: wrong plaintext: got %x, expected %x", i, plaintextCopy, plaintext)
+		}
+	}
+}
+
+func TestCFBInverse(t *testing.T) {
+	block, err := aes.NewCipher(commonKey128)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	plaintext := []byte("this is the plaintext. this is the plaintext.")
+	iv := make([]byte, block.BlockSize())
+	rand.Reader.Read(iv)
+	cfb := cipher.NewCFBEncrypter(block, iv)
+	ciphertext := make([]byte, len(plaintext))
+	copy(ciphertext, plaintext)
+	cfb.XORKeyStream(ciphertext, ciphertext)
+
+	cfbdec := cipher.NewCFBDecrypter(block, iv)
+	plaintextCopy := make([]byte, len(plaintext))
+	copy(plaintextCopy, ciphertext)
+	cfbdec.XORKeyStream(plaintextCopy, plaintextCopy)
+
+	if !bytes.Equal(plaintextCopy, plaintext) {
+		t.Errorf("got: %x, want: %x", plaintextCopy, plaintext)
+	}
+}
diff --git a/src/crypto/cipher/cipher.go b/src/crypto/cipher/cipher.go
new file mode 100644
index 000000000..67afdb1e0
--- /dev/null
+++ b/src/crypto/cipher/cipher.go
@@ -0,0 +1,53 @@
+// Copyright 2010 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 cipher implements standard block cipher modes that can be wrapped
+// around low-level block cipher implementations.
+// See http://csrc.nist.gov/groups/ST/toolkit/BCM/current_modes.html
+// and NIST Special Publication 800-38A.
+package cipher
+
+// A Block represents an implementation of block cipher
+// using a given key.  It provides the capability to encrypt
+// or decrypt individual blocks.  The mode implementations
+// extend that capability to streams of blocks.
+type Block interface {
+	// BlockSize returns the cipher's block size.
+	BlockSize() int
+
+	// Encrypt encrypts the first block in src into dst.
+	// Dst and src may point at the same memory.
+	Encrypt(dst, src []byte)
+
+	// Decrypt decrypts the first block in src into dst.
+	// Dst and src may point at the same memory.
+	Decrypt(dst, src []byte)
+}
+
+// A Stream represents a stream cipher.
+type Stream interface {
+	// XORKeyStream XORs each byte in the given slice with a byte from the
+	// cipher's key stream. Dst and src may point to the same memory.
+	XORKeyStream(dst, src []byte)
+}
+
+// A BlockMode represents a block cipher running in a block-based mode (CBC,
+// ECB etc).
+type BlockMode interface {
+	// BlockSize returns the mode's block size.
+	BlockSize() int
+
+	// CryptBlocks encrypts or decrypts a number of blocks. The length of
+	// src must be a multiple of the block size. Dst and src may point to
+	// the same memory.
+	CryptBlocks(dst, src []byte)
+}
+
+// Utility routines
+
+func dup(p []byte) []byte {
+	q := make([]byte, len(p))
+	copy(q, p)
+	return q
+}
diff --git a/src/crypto/cipher/cipher_test.go b/src/crypto/cipher/cipher_test.go
new file mode 100644
index 000000000..8da5bce93
--- /dev/null
+++ b/src/crypto/cipher/cipher_test.go
@@ -0,0 +1,36 @@
+// Copyright 2013 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 cipher_test
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"testing"
+)
+
+func TestCryptBlocks(t *testing.T) {
+	buf := make([]byte, 16)
+	block, _ := aes.NewCipher(buf)
+
+	mode := cipher.NewCBCDecrypter(block, buf)
+	mustPanic(t, "crypto/cipher: input not full blocks", func() { mode.CryptBlocks(buf, buf[:3]) })
+	mustPanic(t, "crypto/cipher: output smaller than input", func() { mode.CryptBlocks(buf[:3], buf) })
+
+	mode = cipher.NewCBCEncrypter(block, buf)
+	mustPanic(t, "crypto/cipher: input not full blocks", func() { mode.CryptBlocks(buf, buf[:3]) })
+	mustPanic(t, "crypto/cipher: output smaller than input", func() { mode.CryptBlocks(buf[:3], buf) })
+}
+
+func mustPanic(t *testing.T, msg string, f func()) {
+	defer func() {
+		err := recover()
+		if err == nil {
+			t.Errorf("function did not panic, wanted %q", msg)
+		} else if err != msg {
+			t.Errorf("got panic %v, wanted %q", err, msg)
+		}
+	}()
+	f()
+}
diff --git a/src/crypto/cipher/common_test.go b/src/crypto/cipher/common_test.go
new file mode 100644
index 000000000..c75c919d1
--- /dev/null
+++ b/src/crypto/cipher/common_test.go
@@ -0,0 +1,28 @@
+// Copyright 2009 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 cipher_test
+
+// Common values for tests.
+
+var commonInput = []byte{
+	0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
+	0xae, 0x2d, 0x8a, 0x57, 0x1e, 0x03, 0xac, 0x9c, 0x9e, 0xb7, 0x6f, 0xac, 0x45, 0xaf, 0x8e, 0x51,
+	0x30, 0xc8, 0x1c, 0x46, 0xa3, 0x5c, 0xe4, 0x11, 0xe5, 0xfb, 0xc1, 0x19, 0x1a, 0x0a, 0x52, 0xef,
+	0xf6, 0x9f, 0x24, 0x45, 0xdf, 0x4f, 0x9b, 0x17, 0xad, 0x2b, 0x41, 0x7b, 0xe6, 0x6c, 0x37, 0x10,
+}
+
+var commonKey128 = []byte{0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c}
+
+var commonKey192 = []byte{
+	0x8e, 0x73, 0xb0, 0xf7, 0xda, 0x0e, 0x64, 0x52, 0xc8, 0x10, 0xf3, 0x2b, 0x80, 0x90, 0x79, 0xe5,
+	0x62, 0xf8, 0xea, 0xd2, 0x52, 0x2c, 0x6b, 0x7b,
+}
+
+var commonKey256 = []byte{
+	0x60, 0x3d, 0xeb, 0x10, 0x15, 0xca, 0x71, 0xbe, 0x2b, 0x73, 0xae, 0xf0, 0x85, 0x7d, 0x77, 0x81,
+	0x1f, 0x35, 0x2c, 0x07, 0x3b, 0x61, 0x08, 0xd7, 0x2d, 0x98, 0x10, 0xa3, 0x09, 0x14, 0xdf, 0xf4,
+}
+
+var commonIV = []byte{0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f}
diff --git a/src/crypto/cipher/ctr.go b/src/crypto/cipher/ctr.go
new file mode 100644
index 000000000..70ac40f6a
--- /dev/null
+++ b/src/crypto/cipher/ctr.go
@@ -0,0 +1,76 @@
+// Copyright 2009 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.
+
+// Counter (CTR) mode.
+
+// CTR converts a block cipher into a stream cipher by
+// repeatedly encrypting an incrementing counter and
+// xoring the resulting stream of data with the input.
+
+// See NIST SP 800-38A, pp 13-15
+
+package cipher
+
+type ctr struct {
+	b       Block
+	ctr     []byte
+	out     []byte
+	outUsed int
+}
+
+const streamBufferSize = 512
+
+// NewCTR returns a Stream which encrypts/decrypts using the given Block in
+// counter mode. The length of iv must be the same as the Block's block size.
+func NewCTR(block Block, iv []byte) Stream {
+	if len(iv) != block.BlockSize() {
+		panic("cipher.NewCTR: IV length must equal block size")
+	}
+	bufSize := streamBufferSize
+	if bufSize < block.BlockSize() {
+		bufSize = block.BlockSize()
+	}
+	return &ctr{
+		b:       block,
+		ctr:     dup(iv),
+		out:     make([]byte, 0, bufSize),
+		outUsed: 0,
+	}
+}
+
+func (x *ctr) refill() {
+	remain := len(x.out) - x.outUsed
+	if remain > x.outUsed {
+		return
+	}
+	copy(x.out, x.out[x.outUsed:])
+	x.out = x.out[:cap(x.out)]
+	bs := x.b.BlockSize()
+	for remain < len(x.out)-bs {
+		x.b.Encrypt(x.out[remain:], x.ctr)
+		remain += bs
+
+		// Increment counter
+		for i := len(x.ctr) - 1; i >= 0; i-- {
+			x.ctr[i]++
+			if x.ctr[i] != 0 {
+				break
+			}
+		}
+	}
+	x.out = x.out[:remain]
+	x.outUsed = 0
+}
+
+func (x *ctr) XORKeyStream(dst, src []byte) {
+	for len(src) > 0 {
+		if x.outUsed >= len(x.out)-x.b.BlockSize() {
+			x.refill()
+		}
+		n := xorBytes(dst, src, x.out[x.outUsed:])
+		dst = dst[n:]
+		src = src[n:]
+		x.outUsed += n
+	}
+}
diff --git a/src/crypto/cipher/ctr_aes_test.go b/src/crypto/cipher/ctr_aes_test.go
new file mode 100644
index 000000000..d019ae0d0
--- /dev/null
+++ b/src/crypto/cipher/ctr_aes_test.go
@@ -0,0 +1,102 @@
+// Copyright 2009 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.
+
+// CTR AES test vectors.
+
+// See U.S. National Institute of Standards and Technology (NIST)
+// Special Publication 800-38A, ``Recommendation for Block Cipher
+// Modes of Operation,'' 2001 Edition, pp. 55-58.
+
+package cipher_test
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"testing"
+)
+
+var commonCounter = []byte{0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff}
+
+var ctrAESTests = []struct {
+	name string
+	key  []byte
+	iv   []byte
+	in   []byte
+	out  []byte
+}{
+	// NIST SP 800-38A pp 55-58
+	{
+		"CTR-AES128",
+		commonKey128,
+		commonCounter,
+		commonInput,
+		[]byte{
+			0x87, 0x4d, 0x61, 0x91, 0xb6, 0x20, 0xe3, 0x26, 0x1b, 0xef, 0x68, 0x64, 0x99, 0x0d, 0xb6, 0xce,
+			0x98, 0x06, 0xf6, 0x6b, 0x79, 0x70, 0xfd, 0xff, 0x86, 0x17, 0x18, 0x7b, 0xb9, 0xff, 0xfd, 0xff,
+			0x5a, 0xe4, 0xdf, 0x3e, 0xdb, 0xd5, 0xd3, 0x5e, 0x5b, 0x4f, 0x09, 0x02, 0x0d, 0xb0, 0x3e, 0xab,
+			0x1e, 0x03, 0x1d, 0xda, 0x2f, 0xbe, 0x03, 0xd1, 0x79, 0x21, 0x70, 0xa0, 0xf3, 0x00, 0x9c, 0xee,
+		},
+	},
+	{
+		"CTR-AES192",
+		commonKey192,
+		commonCounter,
+		commonInput,
+		[]byte{
+			0x1a, 0xbc, 0x93, 0x24, 0x17, 0x52, 0x1c, 0xa2, 0x4f, 0x2b, 0x04, 0x59, 0xfe, 0x7e, 0x6e, 0x0b,
+			0x09, 0x03, 0x39, 0xec, 0x0a, 0xa6, 0xfa, 0xef, 0xd5, 0xcc, 0xc2, 0xc6, 0xf4, 0xce, 0x8e, 0x94,
+			0x1e, 0x36, 0xb2, 0x6b, 0xd1, 0xeb, 0xc6, 0x70, 0xd1, 0xbd, 0x1d, 0x66, 0x56, 0x20, 0xab, 0xf7,
+			0x4f, 0x78, 0xa7, 0xf6, 0xd2, 0x98, 0x09, 0x58, 0x5a, 0x97, 0xda, 0xec, 0x58, 0xc6, 0xb0, 0x50,
+		},
+	},
+	{
+		"CTR-AES256",
+		commonKey256,
+		commonCounter,
+		commonInput,
+		[]byte{
+			0x60, 0x1e, 0xc3, 0x13, 0x77, 0x57, 0x89, 0xa5, 0xb7, 0xa7, 0xf5, 0x04, 0xbb, 0xf3, 0xd2, 0x28,
+			0xf4, 0x43, 0xe3, 0xca, 0x4d, 0x62, 0xb5, 0x9a, 0xca, 0x84, 0xe9, 0x90, 0xca, 0xca, 0xf5, 0xc5,
+			0x2b, 0x09, 0x30, 0xda, 0xa2, 0x3d, 0xe9, 0x4c, 0xe8, 0x70, 0x17, 0xba, 0x2d, 0x84, 0x98, 0x8d,
+			0xdf, 0xc9, 0xc5, 0x8d, 0xb6, 0x7a, 0xad, 0xa6, 0x13, 0xc2, 0xdd, 0x08, 0x45, 0x79, 0x41, 0xa6,
+		},
+	},
+}
+
+func TestCTR_AES(t *testing.T) {
+	for _, tt := range ctrAESTests {
+		test := tt.name
+
+		c, err := aes.NewCipher(tt.key)
+		if err != nil {
+			t.Errorf("%s: NewCipher(%d bytes) = %s", test, len(tt.key), err)
+			continue
+		}
+
+		for j := 0; j <= 5; j += 5 {
+			in := tt.in[0 : len(tt.in)-j]
+			ctr := cipher.NewCTR(c, tt.iv)
+			encrypted := make([]byte, len(in))
+			ctr.XORKeyStream(encrypted, in)
+			if out := tt.out[0:len(in)]; !bytes.Equal(out, encrypted) {
+				t.Errorf("%s/%d: CTR\ninpt %x\nhave %x\nwant %x", test, len(in), in, encrypted, out)
+			}
+		}
+
+		for j := 0; j <= 7; j += 7 {
+			in := tt.out[0 : len(tt.out)-j]
+			ctr := cipher.NewCTR(c, tt.iv)
+			plain := make([]byte, len(in))
+			ctr.XORKeyStream(plain, in)
+			if out := tt.in[0:len(in)]; !bytes.Equal(out, plain) {
+				t.Errorf("%s/%d: CTRReader\nhave %x\nwant %x", test, len(out), plain, out)
+			}
+		}
+
+		if t.Failed() {
+			break
+		}
+	}
+}
diff --git a/src/crypto/cipher/example_test.go b/src/crypto/cipher/example_test.go
new file mode 100644
index 000000000..1cfa982df
--- /dev/null
+++ b/src/crypto/cipher/example_test.go
@@ -0,0 +1,283 @@
+// Copyright 2012 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 cipher_test
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"os"
+)
+
+func ExampleNewCBCDecrypter() {
+	key := []byte("example key 1234")
+	ciphertext, _ := hex.DecodeString("f363f3ccdcb12bb883abf484ba77d9cd7d32b5baecb3d4b1b3e0e4beffdb3ded")
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// The IV needs to be unique, but not secure. Therefore it's common to
+	// include it at the beginning of the ciphertext.
+	if len(ciphertext) < aes.BlockSize {
+		panic("ciphertext too short")
+	}
+	iv := ciphertext[:aes.BlockSize]
+	ciphertext = ciphertext[aes.BlockSize:]
+
+	// CBC mode always works in whole blocks.
+	if len(ciphertext)%aes.BlockSize != 0 {
+		panic("ciphertext is not a multiple of the block size")
+	}
+
+	mode := cipher.NewCBCDecrypter(block, iv)
+
+	// CryptBlocks can work in-place if the two arguments are the same.
+	mode.CryptBlocks(ciphertext, ciphertext)
+
+	// If the original plaintext lengths are not a multiple of the block
+	// size, padding would have to be added when encrypting, which would be
+	// removed at this point. For an example, see
+	// https://tools.ietf.org/html/rfc5246#section-6.2.3.2. However, it's
+	// critical to note that ciphertexts must be authenticated (i.e. by
+	// using crypto/hmac) before being decrypted in order to avoid creating
+	// a padding oracle.
+
+	fmt.Printf("%s\n", ciphertext)
+	// Output: exampleplaintext
+}
+
+func ExampleNewCBCEncrypter() {
+	key := []byte("example key 1234")
+	plaintext := []byte("exampleplaintext")
+
+	// CBC mode works on blocks so plaintexts may need to be padded to the
+	// next whole block. For an example of such padding, see
+	// https://tools.ietf.org/html/rfc5246#section-6.2.3.2. Here we'll
+	// assume that the plaintext is already of the correct length.
+	if len(plaintext)%aes.BlockSize != 0 {
+		panic("plaintext is not a multiple of the block size")
+	}
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// The IV needs to be unique, but not secure. Therefore it's common to
+	// include it at the beginning of the ciphertext.
+	ciphertext := make([]byte, aes.BlockSize+len(plaintext))
+	iv := ciphertext[:aes.BlockSize]
+	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
+		panic(err)
+	}
+
+	mode := cipher.NewCBCEncrypter(block, iv)
+	mode.CryptBlocks(ciphertext[aes.BlockSize:], plaintext)
+
+	// It's important to remember that ciphertexts must be authenticated
+	// (i.e. by using crypto/hmac) as well as being encrypted in order to
+	// be secure.
+
+	fmt.Printf("%x\n", ciphertext)
+}
+
+func ExampleNewCFBDecrypter() {
+	key := []byte("example key 1234")
+	ciphertext, _ := hex.DecodeString("22277966616d9bc47177bd02603d08c9a67d5380d0fe8cf3b44438dff7b9")
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// The IV needs to be unique, but not secure. Therefore it's common to
+	// include it at the beginning of the ciphertext.
+	if len(ciphertext) < aes.BlockSize {
+		panic("ciphertext too short")
+	}
+	iv := ciphertext[:aes.BlockSize]
+	ciphertext = ciphertext[aes.BlockSize:]
+
+	stream := cipher.NewCFBDecrypter(block, iv)
+
+	// XORKeyStream can work in-place if the two arguments are the same.
+	stream.XORKeyStream(ciphertext, ciphertext)
+	fmt.Printf("%s", ciphertext)
+	// Output: some plaintext
+}
+
+func ExampleNewCFBEncrypter() {
+	key := []byte("example key 1234")
+	plaintext := []byte("some plaintext")
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// The IV needs to be unique, but not secure. Therefore it's common to
+	// include it at the beginning of the ciphertext.
+	ciphertext := make([]byte, aes.BlockSize+len(plaintext))
+	iv := ciphertext[:aes.BlockSize]
+	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
+		panic(err)
+	}
+
+	stream := cipher.NewCFBEncrypter(block, iv)
+	stream.XORKeyStream(ciphertext[aes.BlockSize:], plaintext)
+
+	// It's important to remember that ciphertexts must be authenticated
+	// (i.e. by using crypto/hmac) as well as being encrypted in order to
+	// be secure.
+}
+
+func ExampleNewCTR() {
+	key := []byte("example key 1234")
+	plaintext := []byte("some plaintext")
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// The IV needs to be unique, but not secure. Therefore it's common to
+	// include it at the beginning of the ciphertext.
+	ciphertext := make([]byte, aes.BlockSize+len(plaintext))
+	iv := ciphertext[:aes.BlockSize]
+	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
+		panic(err)
+	}
+
+	stream := cipher.NewCTR(block, iv)
+	stream.XORKeyStream(ciphertext[aes.BlockSize:], plaintext)
+
+	// It's important to remember that ciphertexts must be authenticated
+	// (i.e. by using crypto/hmac) as well as being encrypted in order to
+	// be secure.
+
+	// CTR mode is the same for both encryption and decryption, so we can
+	// also decrypt that ciphertext with NewCTR.
+
+	plaintext2 := make([]byte, len(plaintext))
+	stream = cipher.NewCTR(block, iv)
+	stream.XORKeyStream(plaintext2, ciphertext[aes.BlockSize:])
+
+	fmt.Printf("%s\n", plaintext2)
+	// Output: some plaintext
+}
+
+func ExampleNewOFB() {
+	key := []byte("example key 1234")
+	plaintext := []byte("some plaintext")
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// The IV needs to be unique, but not secure. Therefore it's common to
+	// include it at the beginning of the ciphertext.
+	ciphertext := make([]byte, aes.BlockSize+len(plaintext))
+	iv := ciphertext[:aes.BlockSize]
+	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
+		panic(err)
+	}
+
+	stream := cipher.NewOFB(block, iv)
+	stream.XORKeyStream(ciphertext[aes.BlockSize:], plaintext)
+
+	// It's important to remember that ciphertexts must be authenticated
+	// (i.e. by using crypto/hmac) as well as being encrypted in order to
+	// be secure.
+
+	// OFB mode is the same for both encryption and decryption, so we can
+	// also decrypt that ciphertext with NewOFB.
+
+	plaintext2 := make([]byte, len(plaintext))
+	stream = cipher.NewOFB(block, iv)
+	stream.XORKeyStream(plaintext2, ciphertext[aes.BlockSize:])
+
+	fmt.Printf("%s\n", plaintext2)
+	// Output: some plaintext
+}
+
+func ExampleStreamReader() {
+	key := []byte("example key 1234")
+
+	inFile, err := os.Open("encrypted-file")
+	if err != nil {
+		panic(err)
+	}
+	defer inFile.Close()
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// If the key is unique for each ciphertext, then it's ok to use a zero
+	// IV.
+	var iv [aes.BlockSize]byte
+	stream := cipher.NewOFB(block, iv[:])
+
+	outFile, err := os.OpenFile("decrypted-file", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		panic(err)
+	}
+	defer outFile.Close()
+
+	reader := &cipher.StreamReader{S: stream, R: inFile}
+	// Copy the input file to the output file, decrypting as we go.
+	if _, err := io.Copy(outFile, reader); err != nil {
+		panic(err)
+	}
+
+	// Note that this example is simplistic in that it omits any
+	// authentication of the encrypted data. If you were actually to use
+	// StreamReader in this manner, an attacker could flip arbitrary bits in
+	// the output.
+}
+
+func ExampleStreamWriter() {
+	key := []byte("example key 1234")
+
+	inFile, err := os.Open("plaintext-file")
+	if err != nil {
+		panic(err)
+	}
+	defer inFile.Close()
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// If the key is unique for each ciphertext, then it's ok to use a zero
+	// IV.
+	var iv [aes.BlockSize]byte
+	stream := cipher.NewOFB(block, iv[:])
+
+	outFile, err := os.OpenFile("encrypted-file", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		panic(err)
+	}
+	defer outFile.Close()
+
+	writer := &cipher.StreamWriter{S: stream, W: outFile}
+	// Copy the input file to the output file, encrypting as we go.
+	if _, err := io.Copy(writer, inFile); err != nil {
+		panic(err)
+	}
+
+	// Note that this example is simplistic in that it omits any
+	// authentication of the encrypted data. If you were actually to use
+	// StreamReader in this manner, an attacker could flip arbitrary bits in
+	// the decrypted result.
+}
diff --git a/src/crypto/cipher/gcm.go b/src/crypto/cipher/gcm.go
new file mode 100644
index 000000000..bdafd85fc
--- /dev/null
+++ b/src/crypto/cipher/gcm.go
@@ -0,0 +1,343 @@
+// Copyright 2013 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 cipher
+
+import (
+	"crypto/subtle"
+	"errors"
+)
+
+// AEAD is a cipher mode providing authenticated encryption with associated
+// data.
+type AEAD interface {
+	// NonceSize returns the size of the nonce that must be passed to Seal
+	// and Open.
+	NonceSize() int
+
+	// Overhead returns the maximum difference between the lengths of a
+	// plaintext and ciphertext.
+	Overhead() int
+
+	// Seal encrypts and authenticates plaintext, authenticates the
+	// additional data and appends the result to dst, returning the updated
+	// slice. The nonce must be NonceSize() bytes long and unique for all
+	// time, for a given key.
+	//
+	// The plaintext and dst may alias exactly or not at all.
+	Seal(dst, nonce, plaintext, data []byte) []byte
+
+	// Open decrypts and authenticates ciphertext, authenticates the
+	// additional data and, if successful, appends the resulting plaintext
+	// to dst, returning the updated slice. The nonce must be NonceSize()
+	// bytes long and both it and the additional data must match the
+	// value passed to Seal.
+	//
+	// The ciphertext and dst may alias exactly or not at all.
+	Open(dst, nonce, ciphertext, data []byte) ([]byte, error)
+}
+
+// gcmFieldElement represents a value in GF(2¹²⁸). In order to reflect the GCM
+// standard and make getUint64 suitable for marshaling these values, the bits
+// are stored backwards. For example:
+//   the coefficient of x⁰ can be obtained by v.low >> 63.
+//   the coefficient of x⁶³ can be obtained by v.low & 1.
+//   the coefficient of x⁶⁴ can be obtained by v.high >> 63.
+//   the coefficient of x¹²⁷ can be obtained by v.high & 1.
+type gcmFieldElement struct {
+	low, high uint64
+}
+
+// gcm represents a Galois Counter Mode with a specific key. See
+// http://csrc.nist.gov/groups/ST/toolkit/BCM/documents/proposedmodes/gcm/gcm-revised-spec.pdf
+type gcm struct {
+	cipher Block
+	// productTable contains the first sixteen powers of the key, H.
+	// However, they are in bit reversed order. See NewGCM.
+	productTable [16]gcmFieldElement
+}
+
+// NewGCM returns the given 128-bit, block cipher wrapped in Galois Counter Mode.
+func NewGCM(cipher Block) (AEAD, error) {
+	if cipher.BlockSize() != gcmBlockSize {
+		return nil, errors.New("cipher: NewGCM requires 128-bit block cipher")
+	}
+
+	var key [gcmBlockSize]byte
+	cipher.Encrypt(key[:], key[:])
+
+	g := &gcm{cipher: cipher}
+
+	// We precompute 16 multiples of |key|. However, when we do lookups
+	// into this table we'll be using bits from a field element and
+	// therefore the bits will be in the reverse order. So normally one
+	// would expect, say, 4*key to be in index 4 of the table but due to
+	// this bit ordering it will actually be in index 0010 (base 2) = 2.
+	x := gcmFieldElement{
+		getUint64(key[:8]),
+		getUint64(key[8:]),
+	}
+	g.productTable[reverseBits(1)] = x
+
+	for i := 2; i < 16; i += 2 {
+		g.productTable[reverseBits(i)] = gcmDouble(&g.productTable[reverseBits(i/2)])
+		g.productTable[reverseBits(i+1)] = gcmAdd(&g.productTable[reverseBits(i)], &x)
+	}
+
+	return g, nil
+}
+
+const (
+	gcmBlockSize = 16
+	gcmTagSize   = 16
+	gcmNonceSize = 12
+)
+
+func (*gcm) NonceSize() int {
+	return gcmNonceSize
+}
+
+func (*gcm) Overhead() int {
+	return gcmTagSize
+}
+
+func (g *gcm) Seal(dst, nonce, plaintext, data []byte) []byte {
+	if len(nonce) != gcmNonceSize {
+		panic("cipher: incorrect nonce length given to GCM")
+	}
+
+	ret, out := sliceForAppend(dst, len(plaintext)+gcmTagSize)
+
+	// See GCM spec, section 7.1.
+	var counter, tagMask [gcmBlockSize]byte
+	copy(counter[:], nonce)
+	counter[gcmBlockSize-1] = 1
+
+	g.cipher.Encrypt(tagMask[:], counter[:])
+	gcmInc32(&counter)
+
+	g.counterCrypt(out, plaintext, &counter)
+	g.auth(out[len(plaintext):], out[:len(plaintext)], data, &tagMask)
+
+	return ret
+}
+
+var errOpen = errors.New("cipher: message authentication failed")
+
+func (g *gcm) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
+	if len(nonce) != gcmNonceSize {
+		panic("cipher: incorrect nonce length given to GCM")
+	}
+
+	if len(ciphertext) < gcmTagSize {
+		return nil, errOpen
+	}
+	tag := ciphertext[len(ciphertext)-gcmTagSize:]
+	ciphertext = ciphertext[:len(ciphertext)-gcmTagSize]
+
+	// See GCM spec, section 7.1.
+	var counter, tagMask [gcmBlockSize]byte
+	copy(counter[:], nonce)
+	counter[gcmBlockSize-1] = 1
+
+	g.cipher.Encrypt(tagMask[:], counter[:])
+	gcmInc32(&counter)
+
+	var expectedTag [gcmTagSize]byte
+	g.auth(expectedTag[:], ciphertext, data, &tagMask)
+
+	if subtle.ConstantTimeCompare(expectedTag[:], tag) != 1 {
+		return nil, errOpen
+	}
+
+	ret, out := sliceForAppend(dst, len(ciphertext))
+	g.counterCrypt(out, ciphertext, &counter)
+
+	return ret, nil
+}
+
+// reverseBits reverses the order of the bits of 4-bit number in i.
+func reverseBits(i int) int {
+	i = ((i << 2) & 0xc) | ((i >> 2) & 0x3)
+	i = ((i << 1) & 0xa) | ((i >> 1) & 0x5)
+	return i
+}
+
+// gcmAdd adds two elements of GF(2¹²⁸) and returns the sum.
+func gcmAdd(x, y *gcmFieldElement) gcmFieldElement {
+	// Addition in a characteristic 2 field is just XOR.
+	return gcmFieldElement{x.low ^ y.low, x.high ^ y.high}
+}
+
+// gcmDouble returns the result of doubling an element of GF(2¹²⁸).
+func gcmDouble(x *gcmFieldElement) (double gcmFieldElement) {
+	msbSet := x.high&1 == 1
+
+	// Because of the bit-ordering, doubling is actually a right shift.
+	double.high = x.high >> 1
+	double.high |= x.low << 63
+	double.low = x.low >> 1
+
+	// If the most-significant bit was set before shifting then it,
+	// conceptually, becomes a term of x^128. This is greater than the
+	// irreducible polynomial so the result has to be reduced. The
+	// irreducible polynomial is 1+x+x^2+x^7+x^128. We can subtract that to
+	// eliminate the term at x^128 which also means subtracting the other
+	// four terms. In characteristic 2 fields, subtraction == addition ==
+	// XOR.
+	if msbSet {
+		double.low ^= 0xe100000000000000
+	}
+
+	return
+}
+
+var gcmReductionTable = []uint16{
+	0x0000, 0x1c20, 0x3840, 0x2460, 0x7080, 0x6ca0, 0x48c0, 0x54e0,
+	0xe100, 0xfd20, 0xd940, 0xc560, 0x9180, 0x8da0, 0xa9c0, 0xb5e0,
+}
+
+// mul sets y to y*H, where H is the GCM key, fixed during NewGCM.
+func (g *gcm) mul(y *gcmFieldElement) {
+	var z gcmFieldElement
+
+	for i := 0; i < 2; i++ {
+		word := y.high
+		if i == 1 {
+			word = y.low
+		}
+
+		// Multiplication works by multiplying z by 16 and adding in
+		// one of the precomputed multiples of H.
+		for j := 0; j < 64; j += 4 {
+			msw := z.high & 0xf
+			z.high >>= 4
+			z.high |= z.low << 60
+			z.low >>= 4
+			z.low ^= uint64(gcmReductionTable[msw]) << 48
+
+			// the values in |table| are ordered for
+			// little-endian bit positions. See the comment
+			// in NewGCM.
+			t := &g.productTable[word&0xf]
+
+			z.low ^= t.low
+			z.high ^= t.high
+			word >>= 4
+		}
+	}
+
+	*y = z
+}
+
+// updateBlocks extends y with more polynomial terms from blocks, based on
+// Horner's rule. There must be a multiple of gcmBlockSize bytes in blocks.
+func (g *gcm) updateBlocks(y *gcmFieldElement, blocks []byte) {
+	for len(blocks) > 0 {
+		y.low ^= getUint64(blocks)
+		y.high ^= getUint64(blocks[8:])
+		g.mul(y)
+		blocks = blocks[gcmBlockSize:]
+	}
+}
+
+// update extends y with more polynomial terms from data. If data is not a
+// multiple of gcmBlockSize bytes long then the remainder is zero padded.
+func (g *gcm) update(y *gcmFieldElement, data []byte) {
+	fullBlocks := (len(data) >> 4) << 4
+	g.updateBlocks(y, data[:fullBlocks])
+
+	if len(data) != fullBlocks {
+		var partialBlock [gcmBlockSize]byte
+		copy(partialBlock[:], data[fullBlocks:])
+		g.updateBlocks(y, partialBlock[:])
+	}
+}
+
+// gcmInc32 treats the final four bytes of counterBlock as a big-endian value
+// and increments it.
+func gcmInc32(counterBlock *[16]byte) {
+	for i := gcmBlockSize - 1; i >= gcmBlockSize-4; i-- {
+		counterBlock[i]++
+		if counterBlock[i] != 0 {
+			break
+		}
+	}
+}
+
+// sliceForAppend takes a slice and a requested number of bytes. It returns a
+// slice with the contents of the given slice followed by that many bytes and a
+// second slice that aliases into it and contains only the extra bytes. If the
+// original slice has sufficient capacity then no allocation is performed.
+func sliceForAppend(in []byte, n int) (head, tail []byte) {
+	if total := len(in) + n; cap(in) >= total {
+		head = in[:total]
+	} else {
+		head = make([]byte, total)
+		copy(head, in)
+	}
+	tail = head[len(in):]
+	return
+}
+
+// counterCrypt crypts in to out using g.cipher in counter mode.
+func (g *gcm) counterCrypt(out, in []byte, counter *[gcmBlockSize]byte) {
+	var mask [gcmBlockSize]byte
+
+	for len(in) >= gcmBlockSize {
+		g.cipher.Encrypt(mask[:], counter[:])
+		gcmInc32(counter)
+
+		xorWords(out, in, mask[:])
+		out = out[gcmBlockSize:]
+		in = in[gcmBlockSize:]
+	}
+
+	if len(in) > 0 {
+		g.cipher.Encrypt(mask[:], counter[:])
+		gcmInc32(counter)
+		xorBytes(out, in, mask[:])
+	}
+}
+
+// auth calculates GHASH(ciphertext, additionalData), masks the result with
+// tagMask and writes the result to out.
+func (g *gcm) auth(out, ciphertext, additionalData []byte, tagMask *[gcmTagSize]byte) {
+	var y gcmFieldElement
+	g.update(&y, additionalData)
+	g.update(&y, ciphertext)
+
+	y.low ^= uint64(len(additionalData)) * 8
+	y.high ^= uint64(len(ciphertext)) * 8
+
+	g.mul(&y)
+
+	putUint64(out, y.low)
+	putUint64(out[8:], y.high)
+
+	xorWords(out, out, tagMask[:])
+}
+
+func getUint64(data []byte) uint64 {
+	r := uint64(data[0])<<56 |
+		uint64(data[1])<<48 |
+		uint64(data[2])<<40 |
+		uint64(data[3])<<32 |
+		uint64(data[4])<<24 |
+		uint64(data[5])<<16 |
+		uint64(data[6])<<8 |
+		uint64(data[7])
+	return r
+}
+
+func putUint64(out []byte, v uint64) {
+	out[0] = byte(v >> 56)
+	out[1] = byte(v >> 48)
+	out[2] = byte(v >> 40)
+	out[3] = byte(v >> 32)
+	out[4] = byte(v >> 24)
+	out[5] = byte(v >> 16)
+	out[6] = byte(v >> 8)
+	out[7] = byte(v)
+}
diff --git a/src/crypto/cipher/gcm_test.go b/src/crypto/cipher/gcm_test.go
new file mode 100644
index 000000000..0c502ce40
--- /dev/null
+++ b/src/crypto/cipher/gcm_test.go
@@ -0,0 +1,159 @@
+// Copyright 2013 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 cipher_test
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"encoding/hex"
+	"testing"
+)
+
+// AES-GCM test vectors taken from gcmEncryptExtIV128.rsp from
+// http://csrc.nist.gov/groups/STM/cavp/index.html.
+var aesGCMTests = []struct {
+	key, nonce, plaintext, ad, result string
+}{
+	{
+		"11754cd72aec309bf52f7687212e8957",
+		"3c819d9a9bed087615030b65",
+		"",
+		"",
+		"250327c674aaf477aef2675748cf6971",
+	},
+	{
+		"ca47248ac0b6f8372a97ac43508308ed",
+		"ffd2b598feabc9019262d2be",
+		"",
+		"",
+		"60d20404af527d248d893ae495707d1a",
+	},
+	{
+		"77be63708971c4e240d1cb79e8d77feb",
+		"e0e00f19fed7ba0136a797f3",
+		"",
+		"7a43ec1d9c0a5a78a0b16533a6213cab",
+		"209fcc8d3675ed938e9c7166709dd946",
+	},
+	{
+		"7680c5d3ca6154758e510f4d25b98820",
+		"f8f105f9c3df4965780321f8",
+		"",
+		"c94c410194c765e3dcc7964379758ed3",
+		"94dca8edfcf90bb74b153c8d48a17930",
+	},
+	{
+		"7fddb57453c241d03efbed3ac44e371c",
+		"ee283a3fc75575e33efd4887",
+		"d5de42b461646c255c87bd2962d3b9a2",
+		"",
+		"2ccda4a5415cb91e135c2a0f78c9b2fdb36d1df9b9d5e596f83e8b7f52971cb3",
+	},
+	{
+		"ab72c77b97cb5fe9a382d9fe81ffdbed",
+		"54cc7dc2c37ec006bcc6d1da",
+		"007c5e5b3e59df24a7c355584fc1518d",
+		"",
+		"0e1bde206a07a9c2c1b65300f8c649972b4401346697138c7a4891ee59867d0c",
+	},
+	{
+		"fe47fcce5fc32665d2ae399e4eec72ba",
+		"5adb9609dbaeb58cbd6e7275",
+		"7c0e88c88899a779228465074797cd4c2e1498d259b54390b85e3eef1c02df60e743f1b840382c4bccaf3bafb4ca8429bea063",
+		"88319d6e1d3ffa5f987199166c8a9b56c2aeba5a",
+		"98f4826f05a265e6dd2be82db241c0fbbbf9ffb1c173aa83964b7cf5393043736365253ddbc5db8778371495da76d269e5db3e291ef1982e4defedaa2249f898556b47",
+	},
+	{
+		"ec0c2ba17aa95cd6afffe949da9cc3a8",
+		"296bce5b50b7d66096d627ef",
+		"b85b3753535b825cbe5f632c0b843c741351f18aa484281aebec2f45bb9eea2d79d987b764b9611f6c0f8641843d5d58f3a242",
+		"f8d00f05d22bf68599bcdeb131292ad6e2df5d14",
+		"a7443d31c26bdf2a1c945e29ee4bd344a99cfaf3aa71f8b3f191f83c2adfc7a07162995506fde6309ffc19e716eddf1a828c5a890147971946b627c40016da1ecf3e77",
+	},
+	{
+		"2c1f21cf0f6fb3661943155c3e3d8492",
+		"23cb5ff362e22426984d1907",
+		"42f758836986954db44bf37c6ef5e4ac0adaf38f27252a1b82d02ea949c8a1a2dbc0d68b5615ba7c1220ff6510e259f06655d8",
+		"5d3624879d35e46849953e45a32a624d6a6c536ed9857c613b572b0333e701557a713e3f010ecdf9a6bd6c9e3e44b065208645aff4aabee611b391528514170084ccf587177f4488f33cfb5e979e42b6e1cfc0a60238982a7aec",
+		"81824f0e0d523db30d3da369fdc0d60894c7a0a20646dd015073ad2732bd989b14a222b6ad57af43e1895df9dca2a5344a62cc57a3ee28136e94c74838997ae9823f3a",
+	},
+	{
+		"d9f7d2411091f947b4d6f1e2d1f0fb2e",
+		"e1934f5db57cc983e6b180e7",
+		"73ed042327f70fe9c572a61545eda8b2a0c6e1d6c291ef19248e973aee6c312012f490c2c6f6166f4a59431e182663fcaea05a",
+		"0a8a18a7150e940c3d87b38e73baee9a5c049ee21795663e264b694a949822b639092d0e67015e86363583fcf0ca645af9f43375f05fdb4ce84f411dcbca73c2220dea03a20115d2e51398344b16bee1ed7c499b353d6c597af8",
+		"aaadbd5c92e9151ce3db7210b8714126b73e43436d242677afa50384f2149b831f1d573c7891c2a91fbc48db29967ec9542b2321b51ca862cb637cdd03b99a0f93b134",
+	},
+	{
+		"fe9bb47deb3a61e423c2231841cfd1fb",
+		"4d328eb776f500a2f7fb47aa",
+		"f1cc3818e421876bb6b8bbd6c9",
+		"",
+		"b88c5c1977b35b517b0aeae96743fd4727fe5cdb4b5b42818dea7ef8c9",
+	},
+	{
+		"6703df3701a7f54911ca72e24dca046a",
+		"12823ab601c350ea4bc2488c",
+		"793cd125b0b84a043e3ac67717",
+		"",
+		"b2051c80014f42f08735a7b0cd38e6bcd29962e5f2c13626b85a877101",
+	},
+}
+
+func TestAESGCM(t *testing.T) {
+	for i, test := range aesGCMTests {
+		key, _ := hex.DecodeString(test.key)
+		aes, err := aes.NewCipher(key)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		nonce, _ := hex.DecodeString(test.nonce)
+		plaintext, _ := hex.DecodeString(test.plaintext)
+		ad, _ := hex.DecodeString(test.ad)
+		aesgcm, err := cipher.NewGCM(aes)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		ct := aesgcm.Seal(nil, nonce, plaintext, ad)
+		if ctHex := hex.EncodeToString(ct); ctHex != test.result {
+			t.Errorf("#%d: got %s, want %s", i, ctHex, test.result)
+			continue
+		}
+
+		plaintext2, err := aesgcm.Open(nil, nonce, ct, ad)
+		if err != nil {
+			t.Errorf("#%d: Open failed", i)
+			continue
+		}
+
+		if !bytes.Equal(plaintext, plaintext2) {
+			t.Errorf("#%d: plaintext's don't match: got %x vs %x", i, plaintext2, plaintext)
+			continue
+		}
+
+		if len(ad) > 0 {
+			ad[0] ^= 0x80
+			if _, err := aesgcm.Open(nil, nonce, ct, ad); err == nil {
+				t.Errorf("#%d: Open was successful after altering additional data", i)
+			}
+			ad[0] ^= 0x80
+		}
+
+		nonce[0] ^= 0x80
+		if _, err := aesgcm.Open(nil, nonce, ct, ad); err == nil {
+			t.Errorf("#%d: Open was successful after altering nonce", i)
+		}
+		nonce[0] ^= 0x80
+
+		ct[0] ^= 0x80
+		if _, err := aesgcm.Open(nil, nonce, ct, ad); err == nil {
+			t.Errorf("#%d: Open was successful after altering ciphertext", i)
+		}
+		ct[0] ^= 0x80
+	}
+}
diff --git a/src/crypto/cipher/io.go b/src/crypto/cipher/io.go
new file mode 100644
index 000000000..3938c0a4c
--- /dev/null
+++ b/src/crypto/cipher/io.go
@@ -0,0 +1,55 @@
+// Copyright 2010 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 cipher
+
+import "io"
+
+// The Stream* objects are so simple that all their members are public. Users
+// can create them themselves.
+
+// StreamReader wraps a Stream into an io.Reader. It calls XORKeyStream
+// to process each slice of data which passes through.
+type StreamReader struct {
+	S Stream
+	R io.Reader
+}
+
+func (r StreamReader) Read(dst []byte) (n int, err error) {
+	n, err = r.R.Read(dst)
+	r.S.XORKeyStream(dst[:n], dst[:n])
+	return
+}
+
+// StreamWriter wraps a Stream into an io.Writer. It calls XORKeyStream
+// to process each slice of data which passes through. If any Write call
+// returns short then the StreamWriter is out of sync and must be discarded.
+// A StreamWriter has no internal buffering; Close does not need
+// to be called to flush write data.
+type StreamWriter struct {
+	S   Stream
+	W   io.Writer
+	Err error // unused
+}
+
+func (w StreamWriter) Write(src []byte) (n int, err error) {
+	c := make([]byte, len(src))
+	w.S.XORKeyStream(c, src)
+	n, err = w.W.Write(c)
+	if n != len(src) {
+		if err == nil { // should never happen
+			err = io.ErrShortWrite
+		}
+	}
+	return
+}
+
+// Close closes the underlying Writer and returns its Close return value, if the Writer
+// is also an io.Closer. Otherwise it returns nil.
+func (w StreamWriter) Close() error {
+	if c, ok := w.W.(io.Closer); ok {
+		return c.Close()
+	}
+	return nil
+}
diff --git a/src/crypto/cipher/ofb.go b/src/crypto/cipher/ofb.go
new file mode 100644
index 000000000..e86ebcb23
--- /dev/null
+++ b/src/crypto/cipher/ofb.go
@@ -0,0 +1,66 @@
+// 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.
+
+// OFB (Output Feedback) Mode.
+
+package cipher
+
+type ofb struct {
+	b       Block
+	cipher  []byte
+	out     []byte
+	outUsed int
+}
+
+// NewOFB returns a Stream that encrypts or decrypts using the block cipher b
+// in output feedback mode. The initialization vector iv's length must be equal
+// to b's block size.
+func NewOFB(b Block, iv []byte) Stream {
+	blockSize := b.BlockSize()
+	if len(iv) != blockSize {
+		return nil
+	}
+	bufSize := streamBufferSize
+	if bufSize < blockSize {
+		bufSize = blockSize
+	}
+	x := &ofb{
+		b:       b,
+		cipher:  make([]byte, blockSize),
+		out:     make([]byte, 0, bufSize),
+		outUsed: 0,
+	}
+
+	copy(x.cipher, iv)
+	return x
+}
+
+func (x *ofb) refill() {
+	bs := x.b.BlockSize()
+	remain := len(x.out) - x.outUsed
+	if remain > x.outUsed {
+		return
+	}
+	copy(x.out, x.out[x.outUsed:])
+	x.out = x.out[:cap(x.out)]
+	for remain < len(x.out)-bs {
+		x.b.Encrypt(x.cipher, x.cipher)
+		copy(x.out[remain:], x.cipher)
+		remain += bs
+	}
+	x.out = x.out[:remain]
+	x.outUsed = 0
+}
+
+func (x *ofb) XORKeyStream(dst, src []byte) {
+	for len(src) > 0 {
+		if x.outUsed >= len(x.out)-x.b.BlockSize() {
+			x.refill()
+		}
+		n := xorBytes(dst, src, x.out[x.outUsed:])
+		dst = dst[n:]
+		src = src[n:]
+		x.outUsed += n
+	}
+}
diff --git a/src/crypto/cipher/ofb_test.go b/src/crypto/cipher/ofb_test.go
new file mode 100644
index 000000000..8d3c5d3a3
--- /dev/null
+++ b/src/crypto/cipher/ofb_test.go
@@ -0,0 +1,102 @@
+// Copyright 2009 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.
+
+// OFB AES test vectors.
+
+// See U.S. National Institute of Standards and Technology (NIST)
+// Special Publication 800-38A, ``Recommendation for Block Cipher
+// Modes of Operation,'' 2001 Edition, pp. 52-55.
+
+package cipher_test
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"testing"
+)
+
+type ofbTest struct {
+	name string
+	key  []byte
+	iv   []byte
+	in   []byte
+	out  []byte
+}
+
+var ofbTests = []ofbTest{
+	// NIST SP 800-38A pp 52-55
+	{
+		"OFB-AES128",
+		commonKey128,
+		commonIV,
+		commonInput,
+		[]byte{
+			0x3b, 0x3f, 0xd9, 0x2e, 0xb7, 0x2d, 0xad, 0x20, 0x33, 0x34, 0x49, 0xf8, 0xe8, 0x3c, 0xfb, 0x4a,
+			0x77, 0x89, 0x50, 0x8d, 0x16, 0x91, 0x8f, 0x03, 0xf5, 0x3c, 0x52, 0xda, 0xc5, 0x4e, 0xd8, 0x25,
+			0x97, 0x40, 0x05, 0x1e, 0x9c, 0x5f, 0xec, 0xf6, 0x43, 0x44, 0xf7, 0xa8, 0x22, 0x60, 0xed, 0xcc,
+			0x30, 0x4c, 0x65, 0x28, 0xf6, 0x59, 0xc7, 0x78, 0x66, 0xa5, 0x10, 0xd9, 0xc1, 0xd6, 0xae, 0x5e,
+		},
+	},
+	{
+		"OFB-AES192",
+		commonKey192,
+		commonIV,
+		commonInput,
+		[]byte{
+			0xcd, 0xc8, 0x0d, 0x6f, 0xdd, 0xf1, 0x8c, 0xab, 0x34, 0xc2, 0x59, 0x09, 0xc9, 0x9a, 0x41, 0x74,
+			0xfc, 0xc2, 0x8b, 0x8d, 0x4c, 0x63, 0x83, 0x7c, 0x09, 0xe8, 0x17, 0x00, 0xc1, 0x10, 0x04, 0x01,
+			0x8d, 0x9a, 0x9a, 0xea, 0xc0, 0xf6, 0x59, 0x6f, 0x55, 0x9c, 0x6d, 0x4d, 0xaf, 0x59, 0xa5, 0xf2,
+			0x6d, 0x9f, 0x20, 0x08, 0x57, 0xca, 0x6c, 0x3e, 0x9c, 0xac, 0x52, 0x4b, 0xd9, 0xac, 0xc9, 0x2a,
+		},
+	},
+	{
+		"OFB-AES256",
+		commonKey256,
+		commonIV,
+		commonInput,
+		[]byte{
+			0xdc, 0x7e, 0x84, 0xbf, 0xda, 0x79, 0x16, 0x4b, 0x7e, 0xcd, 0x84, 0x86, 0x98, 0x5d, 0x38, 0x60,
+			0x4f, 0xeb, 0xdc, 0x67, 0x40, 0xd2, 0x0b, 0x3a, 0xc8, 0x8f, 0x6a, 0xd8, 0x2a, 0x4f, 0xb0, 0x8d,
+			0x71, 0xab, 0x47, 0xa0, 0x86, 0xe8, 0x6e, 0xed, 0xf3, 0x9d, 0x1c, 0x5b, 0xba, 0x97, 0xc4, 0x08,
+			0x01, 0x26, 0x14, 0x1d, 0x67, 0xf3, 0x7b, 0xe8, 0x53, 0x8f, 0x5a, 0x8b, 0xe7, 0x40, 0xe4, 0x84,
+		},
+	},
+}
+
+func TestOFB(t *testing.T) {
+	for _, tt := range ofbTests {
+		test := tt.name
+
+		c, err := aes.NewCipher(tt.key)
+		if err != nil {
+			t.Errorf("%s: NewCipher(%d bytes) = %s", test, len(tt.key), err)
+			continue
+		}
+
+		for j := 0; j <= 5; j += 5 {
+			plaintext := tt.in[0 : len(tt.in)-j]
+			ofb := cipher.NewOFB(c, tt.iv)
+			ciphertext := make([]byte, len(plaintext))
+			ofb.XORKeyStream(ciphertext, plaintext)
+			if !bytes.Equal(ciphertext, tt.out[:len(plaintext)]) {
+				t.Errorf("%s/%d: encrypting\ninput % x\nhave % x\nwant % x", test, len(plaintext), plaintext, ciphertext, tt.out)
+			}
+		}
+
+		for j := 0; j <= 5; j += 5 {
+			ciphertext := tt.out[0 : len(tt.in)-j]
+			ofb := cipher.NewOFB(c, tt.iv)
+			plaintext := make([]byte, len(ciphertext))
+			ofb.XORKeyStream(plaintext, ciphertext)
+			if !bytes.Equal(plaintext, tt.in[:len(ciphertext)]) {
+				t.Errorf("%s/%d: decrypting\nhave % x\nwant % x", test, len(ciphertext), plaintext, tt.in)
+			}
+		}
+
+		if t.Failed() {
+			break
+		}
+	}
+}
diff --git a/src/crypto/cipher/xor.go b/src/crypto/cipher/xor.go
new file mode 100644
index 000000000..f88dc8914
--- /dev/null
+++ b/src/crypto/cipher/xor.go
@@ -0,0 +1,84 @@
+// Copyright 2013 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 cipher
+
+import (
+	"runtime"
+	"unsafe"
+)
+
+const wordSize = int(unsafe.Sizeof(uintptr(0)))
+const supportsUnaligned = runtime.GOARCH == "386" || runtime.GOARCH == "amd64"
+
+// fastXORBytes xors in bulk. It only works on architectures that
+// support unaligned read/writes.
+func fastXORBytes(dst, a, b []byte) int {
+	n := len(a)
+	if len(b) < n {
+		n = len(b)
+	}
+
+	w := n / wordSize
+	if w > 0 {
+		dw := *(*[]uintptr)(unsafe.Pointer(&dst))
+		aw := *(*[]uintptr)(unsafe.Pointer(&a))
+		bw := *(*[]uintptr)(unsafe.Pointer(&b))
+		for i := 0; i < w; i++ {
+			dw[i] = aw[i] ^ bw[i]
+		}
+	}
+
+	for i := (n - n%wordSize); i < n; i++ {
+		dst[i] = a[i] ^ b[i]
+	}
+
+	return n
+}
+
+func safeXORBytes(dst, a, b []byte) int {
+	n := len(a)
+	if len(b) < n {
+		n = len(b)
+	}
+	for i := 0; i < n; i++ {
+		dst[i] = a[i] ^ b[i]
+	}
+	return n
+}
+
+// xorBytes xors the bytes in a and b. The destination is assumed to have enough
+// space. Returns the number of bytes xor'd.
+func xorBytes(dst, a, b []byte) int {
+	if supportsUnaligned {
+		return fastXORBytes(dst, a, b)
+	} else {
+		// TODO(hanwen): if (dst, a, b) have common alignment
+		// we could still try fastXORBytes. It is not clear
+		// how often this happens, and it's only worth it if
+		// the block encryption itself is hardware
+		// accelerated.
+		return safeXORBytes(dst, a, b)
+	}
+}
+
+// fastXORWords XORs multiples of 4 or 8 bytes (depending on architecture.)
+// The arguments are assumed to be of equal length.
+func fastXORWords(dst, a, b []byte) {
+	dw := *(*[]uintptr)(unsafe.Pointer(&dst))
+	aw := *(*[]uintptr)(unsafe.Pointer(&a))
+	bw := *(*[]uintptr)(unsafe.Pointer(&b))
+	n := len(b) / wordSize
+	for i := 0; i < n; i++ {
+		dw[i] = aw[i] ^ bw[i]
+	}
+}
+
+func xorWords(dst, a, b []byte) {
+	if supportsUnaligned {
+		fastXORWords(dst, a, b)
+	} else {
+		safeXORBytes(dst, a, b)
+	}
+}
diff --git a/src/crypto/cipher/xor_test.go b/src/crypto/cipher/xor_test.go
new file mode 100644
index 000000000..cc1c9d72d
--- /dev/null
+++ b/src/crypto/cipher/xor_test.go
@@ -0,0 +1,28 @@
+// Copyright 2013 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 cipher
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestXOR(t *testing.T) {
+	for alignP := 0; alignP < 2; alignP++ {
+		for alignQ := 0; alignQ < 2; alignQ++ {
+			for alignD := 0; alignD < 2; alignD++ {
+				p := make([]byte, 1024)[alignP:]
+				q := make([]byte, 1024)[alignQ:]
+				d1 := make([]byte, 1024+alignD)[alignD:]
+				d2 := make([]byte, 1024+alignD)[alignD:]
+				xorBytes(d1, p, q)
+				safeXORBytes(d2, p, q)
+				if bytes.Compare(d1, d2) != 0 {
+					t.Error("not equal")
+				}
+			}
+		}
+	}
+}