// Copyright 2010 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package cipher implements standard block cipher modes that can be wrapped
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// around low-level block cipher implementations.
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// See https://csrc.nist.gov/groups/ST/toolkit/BCM/current_modes.html
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// and NIST Special Publication 800-38A.
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package cipher
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// A Block represents an implementation of block cipher
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// using a given key. It provides the capability to encrypt
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// or decrypt individual blocks. The mode implementations
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// extend that capability to streams of blocks.
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type Block interface {
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// BlockSize returns the cipher's block size.
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BlockSize() int
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// Encrypt encrypts the first block in src into dst.
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// Dst and src must overlap entirely or not at all.
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Encrypt(dst, src []byte)
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// Decrypt decrypts the first block in src into dst.
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// Dst and src must overlap entirely or not at all.
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Decrypt(dst, src []byte)
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}
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// A Stream represents a stream cipher.
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type Stream interface {
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// XORKeyStream XORs each byte in the given slice with a byte from the
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// cipher's key stream. Dst and src must overlap entirely or not at all.
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//
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// If len(dst) < len(src), XORKeyStream should panic. It is acceptable
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// to pass a dst bigger than src, and in that case, XORKeyStream will
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// only update dst[:len(src)] and will not touch the rest of dst.
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//
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// Multiple calls to XORKeyStream behave as if the concatenation of
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// the src buffers was passed in a single run. That is, Stream
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// maintains state and does not reset at each XORKeyStream call.
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XORKeyStream(dst, src []byte)
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}
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// A BlockMode represents a block cipher running in a block-based mode (CBC,
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// ECB etc).
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type BlockMode interface {
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// BlockSize returns the mode's block size.
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BlockSize() int
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// CryptBlocks encrypts or decrypts a number of blocks. The length of
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// src must be a multiple of the block size. Dst and src must overlap
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// entirely or not at all.
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//
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// If len(dst) < len(src), CryptBlocks should panic. It is acceptable
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// to pass a dst bigger than src, and in that case, CryptBlocks will
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// only update dst[:len(src)] and will not touch the rest of dst.
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//
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// Multiple calls to CryptBlocks behave as if the concatenation of
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// the src buffers was passed in a single run. That is, BlockMode
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// maintains state and does not reset at each CryptBlocks call.
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CryptBlocks(dst, src []byte)
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}
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// Utility routines
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func dup(p []byte) []byte {
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q := make([]byte, len(p))
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copy(q, p)
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return q
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}
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