1 files changed, 78 insertions, 0 deletions
diff --git a/libgo/go/crypto/cipher/cbc.go b/libgo/go/crypto/cipher/cbc.go
new file mode 100644
index 0000000000..4632f882a4
--- /dev/null
+++ b/libgo/go/crypto/cipher/cbc.go
@@ -0,0 +1,78 @@
+// 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 {
+	return (*cbcEncrypter)(newCBC(b, iv))
+}
+
+func (x *cbcEncrypter) BlockSize() int { return x.blockSize }
+
+func (x *cbcEncrypter) CryptBlocks(dst, src []byte) {
+	for len(src) > 0 {
+		for i := 0; i < x.blockSize; i++ {
+			x.iv[i] ^= src[i]
+		}
+		x.b.Encrypt(x.iv, x.iv)
+		for i := 0; i < x.blockSize; i++ {
+			dst[i] = x.iv[i]
+		}
+		src = src[x.blockSize:]
+		dst = dst[x.blockSize:]
+	}
+}
+
+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 as must match the iv used to encrypt the data.
+func NewCBCDecrypter(b Block, iv []byte) BlockMode {
+	return (*cbcDecrypter)(newCBC(b, iv))
+}
+
+func (x *cbcDecrypter) BlockSize() int { return x.blockSize }
+
+func (x *cbcDecrypter) CryptBlocks(dst, src []byte) {
+	for len(src) > 0 {
+		x.b.Decrypt(x.tmp, src[:x.blockSize])
+		for i := 0; i < x.blockSize; i++ {
+			x.tmp[i] ^= x.iv[i]
+			x.iv[i] = src[i]
+			dst[i] = x.tmp[i]
+		}
+
+		src = src[x.blockSize:]
+		dst = dst[x.blockSize:]
+	}
+}