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authorOndřej Surý <ondrej@sury.org>2011-09-13 13:13:40 +0200
committerOndřej Surý <ondrej@sury.org>2011-09-13 13:13:40 +0200
commit5ff4c17907d5b19510a62e08fd8d3b11e62b431d (patch)
treec0650497e988f47be9c6f2324fa692a52dea82e1 /src/pkg/crypto/cipher/cfb.go
parent80f18fc933cf3f3e829c5455a1023d69f7b86e52 (diff)
downloadgolang-upstream/60.tar.gz
Imported Upstream version 60upstream/60
Diffstat (limited to 'src/pkg/crypto/cipher/cfb.go')
-rw-r--r--src/pkg/crypto/cipher/cfb.go64
1 files changed, 64 insertions, 0 deletions
diff --git a/src/pkg/crypto/cipher/cfb.go b/src/pkg/crypto/cipher/cfb.go
new file mode 100644
index 000000000..d14165a86
--- /dev/null
+++ b/src/pkg/crypto/cipher/cfb.go
@@ -0,0 +1,64 @@
+// 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
+ out []byte
+ outUsed int
+ decrypt bool
+}
+
+// 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 {
+ return nil
+ }
+
+ x := &cfb{
+ b: block,
+ out: make([]byte, blockSize),
+ outUsed: 0,
+ decrypt: decrypt,
+ }
+ block.Encrypt(x.out, iv)
+
+ return x
+}
+
+func (x *cfb) XORKeyStream(dst, src []byte) {
+ for i := 0; i < len(src); i++ {
+ if x.outUsed == len(x.out) {
+ x.b.Encrypt(x.out, x.out)
+ x.outUsed = 0
+ }
+
+ if x.decrypt {
+ t := src[i]
+ dst[i] = src[i] ^ x.out[x.outUsed]
+ x.out[x.outUsed] = t
+ } else {
+ x.out[x.outUsed] ^= src[i]
+ dst[i] = x.out[x.outUsed]
+ }
+ x.outUsed++
+ }
+}