68 lines
1.8 KiB
Go
68 lines
1.8 KiB
Go
// Copyright 2009 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 aes
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import "strconv"
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// The AES block size in bytes.
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const BlockSize = 16
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// A Cipher is an instance of AES encryption using a particular key.
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type Cipher struct {
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enc []uint32
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dec []uint32
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}
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type KeySizeError int
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func (k KeySizeError) Error() string {
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return "crypto/aes: invalid key size " + strconv.Itoa(int(k))
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}
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// NewCipher creates and returns a new Cipher.
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// The key argument should be the AES key,
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// either 16, 24, or 32 bytes to select
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// AES-128, AES-192, or AES-256.
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func NewCipher(key []byte) (*Cipher, error) {
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k := len(key)
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switch k {
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default:
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return nil, KeySizeError(k)
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case 16, 24, 32:
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break
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}
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n := k + 28
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c := &Cipher{make([]uint32, n), make([]uint32, n)}
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expandKey(key, c.enc, c.dec)
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return c, nil
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}
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// BlockSize returns the AES block size, 16 bytes.
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// It is necessary to satisfy the Cipher interface in the
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// package "crypto/cipher".
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func (c *Cipher) BlockSize() int { return BlockSize }
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// Encrypt encrypts the 16-byte buffer src using the key k
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// and stores the result in dst.
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// Note that for amounts of data larger than a block,
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// it is not safe to just call Encrypt on successive blocks;
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// instead, use an encryption mode like CBC (see crypto/cipher/cbc.go).
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func (c *Cipher) Encrypt(dst, src []byte) { encryptBlock(c.enc, dst, src) }
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// Decrypt decrypts the 16-byte buffer src using the key k
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// and stores the result in dst.
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func (c *Cipher) Decrypt(dst, src []byte) { decryptBlock(c.dec, dst, src) }
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// Reset zeros the key data, so that it will no longer
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// appear in the process's memory.
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func (c *Cipher) Reset() {
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for i := 0; i < len(c.enc); i++ {
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c.enc[i] = 0
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}
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for i := 0; i < len(c.dec); i++ {
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c.dec[i] = 0
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}
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}
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