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 // If len(dst) < len(src), XORKeyStream should panic. It is acceptable 33 // to pass a dst bigger than src, and in that case, XORKeyStream will 34 // only update dst[:len(src)] and will not touch the rest of dst. 35 XORKeyStream(dst, src []byte) 36 } 37 38 // A BlockMode represents a block cipher running in a block-based mode (CBC, 39 // ECB etc). 40 type BlockMode interface { 41 // BlockSize returns the mode's block size. 42 BlockSize() int 43 44 // CryptBlocks encrypts or decrypts a number of blocks. The length of 45 // src must be a multiple of the block size. Dst and src may point to 46 // the same memory. 47 CryptBlocks(dst, src []byte) 48 } 49 50 // Utility routines 51 52 func dup(p []byte) []byte { 53 q := make([]byte, len(p)) 54 copy(q, p) 55 return q 56 } 57
