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Source file src/crypto/cipher/cipher.go

Documentation: crypto/cipher

     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 https://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  

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