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Source file src/crypto/aes/block.go

Documentation: crypto/aes

  // Copyright 2009 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  // This Go implementation is derived in part from the reference
  // ANSI C implementation, which carries the following notice:
  //
  //	rijndael-alg-fst.c
  //
  //	@version 3.0 (December 2000)
  //
  //	Optimised ANSI C code for the Rijndael cipher (now AES)
  //
  //	@author Vincent Rijmen <vincent.rijmen@esat.kuleuven.ac.be>
  //	@author Antoon Bosselaers <antoon.bosselaers@esat.kuleuven.ac.be>
  //	@author Paulo Barreto <paulo.barreto@terra.com.br>
  //
  //	This code is hereby placed in the public domain.
  //
  //	THIS SOFTWARE IS PROVIDED BY THE AUTHORS ''AS IS'' AND ANY EXPRESS
  //	OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  //	WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  //	ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE
  //	LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  //	CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  //	SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  //	BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  //	WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
  //	OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
  //	EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  //
  // See FIPS 197 for specification, and see Daemen and Rijmen's Rijndael submission
  // for implementation details.
  //	http://www.csrc.nist.gov/publications/fips/fips197/fips-197.pdf
  //	http://csrc.nist.gov/archive/aes/rijndael/Rijndael-ammended.pdf
  
  package aes
  
  // Encrypt one block from src into dst, using the expanded key xk.
  func encryptBlockGo(xk []uint32, dst, src []byte) {
  	var s0, s1, s2, s3, t0, t1, t2, t3 uint32
  
  	s0 = uint32(src[0])<<24 | uint32(src[1])<<16 | uint32(src[2])<<8 | uint32(src[3])
  	s1 = uint32(src[4])<<24 | uint32(src[5])<<16 | uint32(src[6])<<8 | uint32(src[7])
  	s2 = uint32(src[8])<<24 | uint32(src[9])<<16 | uint32(src[10])<<8 | uint32(src[11])
  	s3 = uint32(src[12])<<24 | uint32(src[13])<<16 | uint32(src[14])<<8 | uint32(src[15])
  
  	// First round just XORs input with key.
  	s0 ^= xk[0]
  	s1 ^= xk[1]
  	s2 ^= xk[2]
  	s3 ^= xk[3]
  
  	// Middle rounds shuffle using tables.
  	// Number of rounds is set by length of expanded key.
  	nr := len(xk)/4 - 2 // - 2: one above, one more below
  	k := 4
  	for r := 0; r < nr; r++ {
  		t0 = xk[k+0] ^ te0[uint8(s0>>24)] ^ te1[uint8(s1>>16)] ^ te2[uint8(s2>>8)] ^ te3[uint8(s3)]
  		t1 = xk[k+1] ^ te0[uint8(s1>>24)] ^ te1[uint8(s2>>16)] ^ te2[uint8(s3>>8)] ^ te3[uint8(s0)]
  		t2 = xk[k+2] ^ te0[uint8(s2>>24)] ^ te1[uint8(s3>>16)] ^ te2[uint8(s0>>8)] ^ te3[uint8(s1)]
  		t3 = xk[k+3] ^ te0[uint8(s3>>24)] ^ te1[uint8(s0>>16)] ^ te2[uint8(s1>>8)] ^ te3[uint8(s2)]
  		k += 4
  		s0, s1, s2, s3 = t0, t1, t2, t3
  	}
  
  	// Last round uses s-box directly and XORs to produce output.
  	s0 = uint32(sbox0[t0>>24])<<24 | uint32(sbox0[t1>>16&0xff])<<16 | uint32(sbox0[t2>>8&0xff])<<8 | uint32(sbox0[t3&0xff])
  	s1 = uint32(sbox0[t1>>24])<<24 | uint32(sbox0[t2>>16&0xff])<<16 | uint32(sbox0[t3>>8&0xff])<<8 | uint32(sbox0[t0&0xff])
  	s2 = uint32(sbox0[t2>>24])<<24 | uint32(sbox0[t3>>16&0xff])<<16 | uint32(sbox0[t0>>8&0xff])<<8 | uint32(sbox0[t1&0xff])
  	s3 = uint32(sbox0[t3>>24])<<24 | uint32(sbox0[t0>>16&0xff])<<16 | uint32(sbox0[t1>>8&0xff])<<8 | uint32(sbox0[t2&0xff])
  
  	s0 ^= xk[k+0]
  	s1 ^= xk[k+1]
  	s2 ^= xk[k+2]
  	s3 ^= xk[k+3]
  
  	dst[0], dst[1], dst[2], dst[3] = byte(s0>>24), byte(s0>>16), byte(s0>>8), byte(s0)
  	dst[4], dst[5], dst[6], dst[7] = byte(s1>>24), byte(s1>>16), byte(s1>>8), byte(s1)
  	dst[8], dst[9], dst[10], dst[11] = byte(s2>>24), byte(s2>>16), byte(s2>>8), byte(s2)
  	dst[12], dst[13], dst[14], dst[15] = byte(s3>>24), byte(s3>>16), byte(s3>>8), byte(s3)
  }
  
  // Decrypt one block from src into dst, using the expanded key xk.
  func decryptBlockGo(xk []uint32, dst, src []byte) {
  	var s0, s1, s2, s3, t0, t1, t2, t3 uint32
  
  	s0 = uint32(src[0])<<24 | uint32(src[1])<<16 | uint32(src[2])<<8 | uint32(src[3])
  	s1 = uint32(src[4])<<24 | uint32(src[5])<<16 | uint32(src[6])<<8 | uint32(src[7])
  	s2 = uint32(src[8])<<24 | uint32(src[9])<<16 | uint32(src[10])<<8 | uint32(src[11])
  	s3 = uint32(src[12])<<24 | uint32(src[13])<<16 | uint32(src[14])<<8 | uint32(src[15])
  
  	// First round just XORs input with key.
  	s0 ^= xk[0]
  	s1 ^= xk[1]
  	s2 ^= xk[2]
  	s3 ^= xk[3]
  
  	// Middle rounds shuffle using tables.
  	// Number of rounds is set by length of expanded key.
  	nr := len(xk)/4 - 2 // - 2: one above, one more below
  	k := 4
  	for r := 0; r < nr; r++ {
  		t0 = xk[k+0] ^ td0[uint8(s0>>24)] ^ td1[uint8(s3>>16)] ^ td2[uint8(s2>>8)] ^ td3[uint8(s1)]
  		t1 = xk[k+1] ^ td0[uint8(s1>>24)] ^ td1[uint8(s0>>16)] ^ td2[uint8(s3>>8)] ^ td3[uint8(s2)]
  		t2 = xk[k+2] ^ td0[uint8(s2>>24)] ^ td1[uint8(s1>>16)] ^ td2[uint8(s0>>8)] ^ td3[uint8(s3)]
  		t3 = xk[k+3] ^ td0[uint8(s3>>24)] ^ td1[uint8(s2>>16)] ^ td2[uint8(s1>>8)] ^ td3[uint8(s0)]
  		k += 4
  		s0, s1, s2, s3 = t0, t1, t2, t3
  	}
  
  	// Last round uses s-box directly and XORs to produce output.
  	s0 = uint32(sbox1[t0>>24])<<24 | uint32(sbox1[t3>>16&0xff])<<16 | uint32(sbox1[t2>>8&0xff])<<8 | uint32(sbox1[t1&0xff])
  	s1 = uint32(sbox1[t1>>24])<<24 | uint32(sbox1[t0>>16&0xff])<<16 | uint32(sbox1[t3>>8&0xff])<<8 | uint32(sbox1[t2&0xff])
  	s2 = uint32(sbox1[t2>>24])<<24 | uint32(sbox1[t1>>16&0xff])<<16 | uint32(sbox1[t0>>8&0xff])<<8 | uint32(sbox1[t3&0xff])
  	s3 = uint32(sbox1[t3>>24])<<24 | uint32(sbox1[t2>>16&0xff])<<16 | uint32(sbox1[t1>>8&0xff])<<8 | uint32(sbox1[t0&0xff])
  
  	s0 ^= xk[k+0]
  	s1 ^= xk[k+1]
  	s2 ^= xk[k+2]
  	s3 ^= xk[k+3]
  
  	dst[0], dst[1], dst[2], dst[3] = byte(s0>>24), byte(s0>>16), byte(s0>>8), byte(s0)
  	dst[4], dst[5], dst[6], dst[7] = byte(s1>>24), byte(s1>>16), byte(s1>>8), byte(s1)
  	dst[8], dst[9], dst[10], dst[11] = byte(s2>>24), byte(s2>>16), byte(s2>>8), byte(s2)
  	dst[12], dst[13], dst[14], dst[15] = byte(s3>>24), byte(s3>>16), byte(s3>>8), byte(s3)
  }
  
  // Apply sbox0 to each byte in w.
  func subw(w uint32) uint32 {
  	return uint32(sbox0[w>>24])<<24 |
  		uint32(sbox0[w>>16&0xff])<<16 |
  		uint32(sbox0[w>>8&0xff])<<8 |
  		uint32(sbox0[w&0xff])
  }
  
  // Rotate
  func rotw(w uint32) uint32 { return w<<8 | w>>24 }
  
  // Key expansion algorithm. See FIPS-197, Figure 11.
  // Their rcon[i] is our powx[i-1] << 24.
  func expandKeyGo(key []byte, enc, dec []uint32) {
  	// Encryption key setup.
  	var i int
  	nk := len(key) / 4
  	for i = 0; i < nk; i++ {
  		enc[i] = uint32(key[4*i])<<24 | uint32(key[4*i+1])<<16 | uint32(key[4*i+2])<<8 | uint32(key[4*i+3])
  	}
  	for ; i < len(enc); i++ {
  		t := enc[i-1]
  		if i%nk == 0 {
  			t = subw(rotw(t)) ^ (uint32(powx[i/nk-1]) << 24)
  		} else if nk > 6 && i%nk == 4 {
  			t = subw(t)
  		}
  		enc[i] = enc[i-nk] ^ t
  	}
  
  	// Derive decryption key from encryption key.
  	// Reverse the 4-word round key sets from enc to produce dec.
  	// All sets but the first and last get the MixColumn transform applied.
  	if dec == nil {
  		return
  	}
  	n := len(enc)
  	for i := 0; i < n; i += 4 {
  		ei := n - i - 4
  		for j := 0; j < 4; j++ {
  			x := enc[ei+j]
  			if i > 0 && i+4 < n {
  				x = td0[sbox0[x>>24]] ^ td1[sbox0[x>>16&0xff]] ^ td2[sbox0[x>>8&0xff]] ^ td3[sbox0[x&0xff]]
  			}
  			dec[i+j] = x
  		}
  	}
  }
  

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