mirror of
https://github.com/autc04/Retro68.git
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111 lines
2.7 KiB
Go
111 lines
2.7 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Cipher block chaining (CBC) mode.
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// CBC provides confidentiality by xoring (chaining) each plaintext block
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// with the previous ciphertext block before applying the block cipher.
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// See NIST SP 800-38A, pp 10-11
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package cipher
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type cbc struct {
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b Block
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blockSize int
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iv []byte
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tmp []byte
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}
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func newCBC(b Block, iv []byte) *cbc {
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return &cbc{
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b: b,
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blockSize: b.BlockSize(),
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iv: dup(iv),
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tmp: make([]byte, b.BlockSize()),
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}
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}
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type cbcEncrypter cbc
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// NewCBCEncrypter returns a BlockMode which encrypts in cipher block chaining
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// mode, using the given Block. The length of iv must be the same as the
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// Block's block size.
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func NewCBCEncrypter(b Block, iv []byte) BlockMode {
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if len(iv) != b.BlockSize() {
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panic("cipher.NewCBCEncrypter: IV length must equal block size")
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}
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return (*cbcEncrypter)(newCBC(b, iv))
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}
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func (x *cbcEncrypter) BlockSize() int { return x.blockSize }
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func (x *cbcEncrypter) CryptBlocks(dst, src []byte) {
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if len(src)%x.blockSize != 0 {
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panic("crypto/cipher: input not full blocks")
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}
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if len(dst) < len(src) {
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panic("crypto/cipher: output smaller than input")
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}
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for len(src) > 0 {
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for i := 0; i < x.blockSize; i++ {
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x.iv[i] ^= src[i]
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}
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x.b.Encrypt(x.iv, x.iv)
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for i := 0; i < x.blockSize; i++ {
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dst[i] = x.iv[i]
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}
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src = src[x.blockSize:]
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dst = dst[x.blockSize:]
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}
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}
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func (x *cbcEncrypter) SetIV(iv []byte) {
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if len(iv) != len(x.iv) {
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panic("cipher: incorrect length IV")
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}
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copy(x.iv, iv)
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}
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type cbcDecrypter cbc
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// NewCBCDecrypter returns a BlockMode which decrypts in cipher block chaining
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// mode, using the given Block. The length of iv must be the same as the
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// Block's block size and must match the iv used to encrypt the data.
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func NewCBCDecrypter(b Block, iv []byte) BlockMode {
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if len(iv) != b.BlockSize() {
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panic("cipher.NewCBCDecrypter: IV length must equal block size")
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}
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return (*cbcDecrypter)(newCBC(b, iv))
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}
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func (x *cbcDecrypter) BlockSize() int { return x.blockSize }
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func (x *cbcDecrypter) CryptBlocks(dst, src []byte) {
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if len(src)%x.blockSize != 0 {
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panic("crypto/cipher: input not full blocks")
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}
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if len(dst) < len(src) {
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panic("crypto/cipher: output smaller than input")
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}
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for len(src) > 0 {
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x.b.Decrypt(x.tmp, src[:x.blockSize])
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for i := 0; i < x.blockSize; i++ {
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x.tmp[i] ^= x.iv[i]
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x.iv[i] = src[i]
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dst[i] = x.tmp[i]
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}
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src = src[x.blockSize:]
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dst = dst[x.blockSize:]
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}
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}
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func (x *cbcDecrypter) SetIV(iv []byte) {
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if len(iv) != len(x.iv) {
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panic("cipher: incorrect length IV")
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}
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copy(x.iv, iv)
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}
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