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 must overlap entirely or not at all. 21 Encrypt(dst, src []byte) 22 23 // Decrypt decrypts the first block in src into dst. 24 // Dst and src must overlap entirely or not at all. 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 must overlap entirely or not at all. 32 // 33 // If len(dst) < len(src), XORKeyStream should panic. It is acceptable 34 // to pass a dst bigger than src, and in that case, XORKeyStream will 35 // only update dst[:len(src)] and will not touch the rest of dst. 36 // 37 // Multiple calls to XORKeyStream behave as if the concatenation of 38 // the src buffers was passed in a single run. That is, Stream 39 // maintains state and does not reset at each XORKeyStream call. 40 XORKeyStream(dst, src []byte) 41 } 42 43 // A BlockMode represents a block cipher running in a block-based mode (CBC, 44 // ECB etc). 45 type BlockMode interface { 46 // BlockSize returns the mode's block size. 47 BlockSize() int 48 49 // CryptBlocks encrypts or decrypts a number of blocks. The length of 50 // src must be a multiple of the block size. Dst and src must overlap 51 // entirely or not at all. 52 // 53 // If len(dst) < len(src), CryptBlocks should panic. It is acceptable 54 // to pass a dst bigger than src, and in that case, CryptBlocks will 55 // only update dst[:len(src)] and will not touch the rest of dst. 56 // 57 // Multiple calls to CryptBlocks behave as if the concatenation of 58 // the src buffers was passed in a single run. That is, BlockMode 59 // maintains state and does not reset at each CryptBlocks call. 60 CryptBlocks(dst, src []byte) 61 } 62 63 // Utility routines 64 65 func dup(p []byte) []byte { 66 q := make([]byte, len(p)) 67 copy(q, p) 68 return q 69 } 70
