Source file src/pkg/crypto/cipher/cipher.go
1 // Copyright 2010 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // Package cipher implements standard block cipher modes that can be wrapped 6 // around low-level block cipher implementations. 7 // See http://csrc.nist.gov/groups/ST/toolkit/BCM/current_modes.html 8 // and NIST Special Publication 800-38A. 9 package cipher 10 11 // A Block represents an implementation of block cipher 12 // using a given key. It provides the capability to encrypt 13 // or decrypt individual blocks. The mode implementations 14 // extend that capability to streams of blocks. 15 type Block interface { 16 // BlockSize returns the cipher's block size. 17 BlockSize() int 18 19 // Encrypt encrypts the first block in src into dst. 20 // Dst and src may point at the same memory. 21 Encrypt(dst, src []byte) 22 23 // Decrypt decrypts the first block in src into dst. 24 // Dst and src may point at the same memory. 25 Decrypt(dst, src []byte) 26 } 27 28 // A Stream represents a stream cipher. 29 type Stream interface { 30 // XORKeyStream XORs each byte in the given slice with a byte from the 31 // cipher's key stream. Dst and src may point to the same memory. 32 XORKeyStream(dst, src []byte) 33 } 34 35 // A BlockMode represents a block cipher running in a block-based mode (CBC, 36 // ECB etc). 37 type BlockMode interface { 38 // BlockSize returns the mode's block size. 39 BlockSize() int 40 41 // CryptBlocks encrypts or decrypts a number of blocks. The length of 42 // src must be a multiple of the block size. Dst and src may point to 43 // the same memory. 44 CryptBlocks(dst, src []byte) 45 } 46 47 // Utility routines 48 49 func shift1(dst, src []byte) byte { 50 var b byte 51 for i := len(src) - 1; i >= 0; i-- { 52 bb := src[i] >> 7 53 dst[i] = src[i]<<1 | b 54 b = bb 55 } 56 return b 57 } 58 59 func dup(p []byte) []byte { 60 q := make([]byte, len(p)) 61 copy(q, p) 62 return q 63 }