block.go

Documentation: crypto/aes

     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  // This Go implementation is derived in part from the reference
     6  // ANSI C implementation, which carries the following notice:
     7  //
     8  //	rijndael-alg-fst.c
     9  //
    10  //	@version 3.0 (December 2000)
    11  //
    12  //	Optimised ANSI C code for the Rijndael cipher (now AES)
    13  //
    14  //	@author Vincent Rijmen <vincent.rijmen@esat.kuleuven.ac.be>
    15  //	@author Antoon Bosselaers <antoon.bosselaers@esat.kuleuven.ac.be>
    16  //	@author Paulo Barreto <paulo.barreto@terra.com.br>
    17  //
    18  //	This code is hereby placed in the public domain.
    19  //
    20  //	THIS SOFTWARE IS PROVIDED BY THE AUTHORS ''AS IS'' AND ANY EXPRESS
    21  //	OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
    22  //	WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    23  //	ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE
    24  //	LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
    25  //	CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
    26  //	SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
    27  //	BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
    28  //	WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
    29  //	OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
    30  //	EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
    31  //
    32  // See FIPS 197 for specification, and see Daemen and Rijmen's Rijndael submission
    33  // for implementation details.
    34  //	http://www.csrc.nist.gov/publications/fips/fips197/fips-197.pdf
    35  //	http://csrc.nist.gov/archive/aes/rijndael/Rijndael-ammended.pdf
    36  
    37  package aes
    38  
    39  // Encrypt one block from src into dst, using the expanded key xk.
    40  func encryptBlockGo(xk []uint32, dst, src []byte) {
    41  	var s0, s1, s2, s3, t0, t1, t2, t3 uint32
    42  
    43  	s0 = uint32(src[0])<<24 | uint32(src[1])<<16 | uint32(src[2])<<8 | uint32(src[3])
    44  	s1 = uint32(src[4])<<24 | uint32(src[5])<<16 | uint32(src[6])<<8 | uint32(src[7])
    45  	s2 = uint32(src[8])<<24 | uint32(src[9])<<16 | uint32(src[10])<<8 | uint32(src[11])
    46  	s3 = uint32(src[12])<<24 | uint32(src[13])<<16 | uint32(src[14])<<8 | uint32(src[15])
    47  
    48  	// First round just XORs input with key.
    49  	s0 ^= xk[0]
    50  	s1 ^= xk[1]
    51  	s2 ^= xk[2]
    52  	s3 ^= xk[3]
    53  
    54  	// Middle rounds shuffle using tables.
    55  	// Number of rounds is set by length of expanded key.
    56  	nr := len(xk)/4 - 2 // - 2: one above, one more below
    57  	k := 4
    58  	for r := 0; r < nr; r++ {
    59  		t0 = xk[k+0] ^ te0[uint8(s0>>24)] ^ te1[uint8(s1>>16)] ^ te2[uint8(s2>>8)] ^ te3[uint8(s3)]
    60  		t1 = xk[k+1] ^ te0[uint8(s1>>24)] ^ te1[uint8(s2>>16)] ^ te2[uint8(s3>>8)] ^ te3[uint8(s0)]
    61  		t2 = xk[k+2] ^ te0[uint8(s2>>24)] ^ te1[uint8(s3>>16)] ^ te2[uint8(s0>>8)] ^ te3[uint8(s1)]
    62  		t3 = xk[k+3] ^ te0[uint8(s3>>24)] ^ te1[uint8(s0>>16)] ^ te2[uint8(s1>>8)] ^ te3[uint8(s2)]
    63  		k += 4
    64  		s0, s1, s2, s3 = t0, t1, t2, t3
    65  	}
    66  
    67  	// Last round uses s-box directly and XORs to produce output.
    68  	s0 = uint32(sbox0[t0>>24])<<24 | uint32(sbox0[t1>>16&0xff])<<16 | uint32(sbox0[t2>>8&0xff])<<8 | uint32(sbox0[t3&0xff])
    69  	s1 = uint32(sbox0[t1>>24])<<24 | uint32(sbox0[t2>>16&0xff])<<16 | uint32(sbox0[t3>>8&0xff])<<8 | uint32(sbox0[t0&0xff])
    70  	s2 = uint32(sbox0[t2>>24])<<24 | uint32(sbox0[t3>>16&0xff])<<16 | uint32(sbox0[t0>>8&0xff])<<8 | uint32(sbox0[t1&0xff])
    71  	s3 = uint32(sbox0[t3>>24])<<24 | uint32(sbox0[t0>>16&0xff])<<16 | uint32(sbox0[t1>>8&0xff])<<8 | uint32(sbox0[t2&0xff])
    72  
    73  	s0 ^= xk[k+0]
    74  	s1 ^= xk[k+1]
    75  	s2 ^= xk[k+2]
    76  	s3 ^= xk[k+3]
    77  
    78  	dst[0], dst[1], dst[2], dst[3] = byte(s0>>24), byte(s0>>16), byte(s0>>8), byte(s0)
    79  	dst[4], dst[5], dst[6], dst[7] = byte(s1>>24), byte(s1>>16), byte(s1>>8), byte(s1)
    80  	dst[8], dst[9], dst[10], dst[11] = byte(s2>>24), byte(s2>>16), byte(s2>>8), byte(s2)
    81  	dst[12], dst[13], dst[14], dst[15] = byte(s3>>24), byte(s3>>16), byte(s3>>8), byte(s3)
    82  }
    83  
    84  // Decrypt one block from src into dst, using the expanded key xk.
    85  func decryptBlockGo(xk []uint32, dst, src []byte) {
    86  	var s0, s1, s2, s3, t0, t1, t2, t3 uint32
    87  
    88  	s0 = uint32(src[0])<<24 | uint32(src[1])<<16 | uint32(src[2])<<8 | uint32(src[3])
    89  	s1 = uint32(src[4])<<24 | uint32(src[5])<<16 | uint32(src[6])<<8 | uint32(src[7])
    90  	s2 = uint32(src[8])<<24 | uint32(src[9])<<16 | uint32(src[10])<<8 | uint32(src[11])
    91  	s3 = uint32(src[12])<<24 | uint32(src[13])<<16 | uint32(src[14])<<8 | uint32(src[15])
    92  
    93  	// First round just XORs input with key.
    94  	s0 ^= xk[0]
    95  	s1 ^= xk[1]
    96  	s2 ^= xk[2]
    97  	s3 ^= xk[3]
    98  
    99  	// Middle rounds shuffle using tables.
   100  	// Number of rounds is set by length of expanded key.
   101  	nr := len(xk)/4 - 2 // - 2: one above, one more below
   102  	k := 4
   103  	for r := 0; r < nr; r++ {
   104  		t0 = xk[k+0] ^ td0[uint8(s0>>24)] ^ td1[uint8(s3>>16)] ^ td2[uint8(s2>>8)] ^ td3[uint8(s1)]
   105  		t1 = xk[k+1] ^ td0[uint8(s1>>24)] ^ td1[uint8(s0>>16)] ^ td2[uint8(s3>>8)] ^ td3[uint8(s2)]
   106  		t2 = xk[k+2] ^ td0[uint8(s2>>24)] ^ td1[uint8(s1>>16)] ^ td2[uint8(s0>>8)] ^ td3[uint8(s3)]
   107  		t3 = xk[k+3] ^ td0[uint8(s3>>24)] ^ td1[uint8(s2>>16)] ^ td2[uint8(s1>>8)] ^ td3[uint8(s0)]
   108  		k += 4
   109  		s0, s1, s2, s3 = t0, t1, t2, t3
   110  	}
   111  
   112  	// Last round uses s-box directly and XORs to produce output.
   113  	s0 = uint32(sbox1[t0>>24])<<24 | uint32(sbox1[t3>>16&0xff])<<16 | uint32(sbox1[t2>>8&0xff])<<8 | uint32(sbox1[t1&0xff])
   114  	s1 = uint32(sbox1[t1>>24])<<24 | uint32(sbox1[t0>>16&0xff])<<16 | uint32(sbox1[t3>>8&0xff])<<8 | uint32(sbox1[t2&0xff])
   115  	s2 = uint32(sbox1[t2>>24])<<24 | uint32(sbox1[t1>>16&0xff])<<16 | uint32(sbox1[t0>>8&0xff])<<8 | uint32(sbox1[t3&0xff])
   116  	s3 = uint32(sbox1[t3>>24])<<24 | uint32(sbox1[t2>>16&0xff])<<16 | uint32(sbox1[t1>>8&0xff])<<8 | uint32(sbox1[t0&0xff])
   117  
   118  	s0 ^= xk[k+0]
   119  	s1 ^= xk[k+1]
   120  	s2 ^= xk[k+2]
   121  	s3 ^= xk[k+3]
   122  
   123  	dst[0], dst[1], dst[2], dst[3] = byte(s0>>24), byte(s0>>16), byte(s0>>8), byte(s0)
   124  	dst[4], dst[5], dst[6], dst[7] = byte(s1>>24), byte(s1>>16), byte(s1>>8), byte(s1)
   125  	dst[8], dst[9], dst[10], dst[11] = byte(s2>>24), byte(s2>>16), byte(s2>>8), byte(s2)
   126  	dst[12], dst[13], dst[14], dst[15] = byte(s3>>24), byte(s3>>16), byte(s3>>8), byte(s3)
   127  }
   128  
   129  // Apply sbox0 to each byte in w.
   130  func subw(w uint32) uint32 {
   131  	return uint32(sbox0[w>>24])<<24 |
   132  		uint32(sbox0[w>>16&0xff])<<16 |
   133  		uint32(sbox0[w>>8&0xff])<<8 |
   134  		uint32(sbox0[w&0xff])
   135  }
   136  
   137  // Rotate
   138  func rotw(w uint32) uint32 { return w<<8 | w>>24 }
   139  
   140  // Key expansion algorithm. See FIPS-197, Figure 11.
   141  // Their rcon[i] is our powx[i-1] << 24.
   142  func expandKeyGo(key []byte, enc, dec []uint32) {
   143  	// Encryption key setup.
   144  	var i int
   145  	nk := len(key) / 4
   146  	for i = 0; i < nk; i++ {
   147  		enc[i] = uint32(key[4*i])<<24 | uint32(key[4*i+1])<<16 | uint32(key[4*i+2])<<8 | uint32(key[4*i+3])
   148  	}
   149  	for ; i < len(enc); i++ {
   150  		t := enc[i-1]
   151  		if i%nk == 0 {
   152  			t = subw(rotw(t)) ^ (uint32(powx[i/nk-1]) << 24)
   153  		} else if nk > 6 && i%nk == 4 {
   154  			t = subw(t)
   155  		}
   156  		enc[i] = enc[i-nk] ^ t
   157  	}
   158  
   159  	// Derive decryption key from encryption key.
   160  	// Reverse the 4-word round key sets from enc to produce dec.
   161  	// All sets but the first and last get the MixColumn transform applied.
   162  	if dec == nil {
   163  		return
   164  	}
   165  	n := len(enc)
   166  	for i := 0; i < n; i += 4 {
   167  		ei := n - i - 4
   168  		for j := 0; j < 4; j++ {
   169  			x := enc[ei+j]
   170  			if i > 0 && i+4 < n {
   171  				x = td0[sbox0[x>>24]] ^ td1[sbox0[x>>16&0xff]] ^ td2[sbox0[x>>8&0xff]] ^ td3[sbox0[x&0xff]]
   172  			}
   173  			dec[i+j] = x
   174  		}
   175  	}
   176  }
   177
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