Source file src/pkg/crypto/aes/cipher.go

     1	// Copyright 2009 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 aes
     6	
     7	import (
     8		"crypto/cipher"
     9		"crypto/internal/subtle"
    10		"strconv"
    11	)
    12	
    13	// The AES block size in bytes.
    14	const BlockSize = 16
    15	
    16	// A cipher is an instance of AES encryption using a particular key.
    17	type aesCipher struct {
    18		enc []uint32
    19		dec []uint32
    20	}
    21	
    22	type KeySizeError int
    23	
    24	func (k KeySizeError) Error() string {
    25		return "crypto/aes: invalid key size " + strconv.Itoa(int(k))
    26	}
    27	
    28	// NewCipher creates and returns a new cipher.Block.
    29	// The key argument should be the AES key,
    30	// either 16, 24, or 32 bytes to select
    31	// AES-128, AES-192, or AES-256.
    32	func NewCipher(key []byte) (cipher.Block, error) {
    33		k := len(key)
    34		switch k {
    35		default:
    36			return nil, KeySizeError(k)
    37		case 16, 24, 32:
    38			break
    39		}
    40		return newCipher(key)
    41	}
    42	
    43	// newCipherGeneric creates and returns a new cipher.Block
    44	// implemented in pure Go.
    45	func newCipherGeneric(key []byte) (cipher.Block, error) {
    46		n := len(key) + 28
    47		c := aesCipher{make([]uint32, n), make([]uint32, n)}
    48		expandKeyGo(key, c.enc, c.dec)
    49		return &c, nil
    50	}
    51	
    52	func (c *aesCipher) BlockSize() int { return BlockSize }
    53	
    54	func (c *aesCipher) Encrypt(dst, src []byte) {
    55		if len(src) < BlockSize {
    56			panic("crypto/aes: input not full block")
    57		}
    58		if len(dst) < BlockSize {
    59			panic("crypto/aes: output not full block")
    60		}
    61		if subtle.InexactOverlap(dst[:BlockSize], src[:BlockSize]) {
    62			panic("crypto/aes: invalid buffer overlap")
    63		}
    64		encryptBlockGo(c.enc, dst, src)
    65	}
    66	
    67	func (c *aesCipher) Decrypt(dst, src []byte) {
    68		if len(src) < BlockSize {
    69			panic("crypto/aes: input not full block")
    70		}
    71		if len(dst) < BlockSize {
    72			panic("crypto/aes: output not full block")
    73		}
    74		if subtle.InexactOverlap(dst[:BlockSize], src[:BlockSize]) {
    75			panic("crypto/aes: invalid buffer overlap")
    76		}
    77		decryptBlockGo(c.dec, dst, src)
    78	}
    79	

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