github.com/varialus/godfly@v0.0.0-20130904042352-1934f9f095ab/src/pkg/crypto/cipher/cipher.go (about)

     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  }