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block.go
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block.go
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// 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.
// https://csrc.nist.gov/csrc/media/publications/fips/197/final/documents/fips-197.pdf
// https://csrc.nist.gov/archive/aes/rijndael/Rijndael-ammended.pdf
package aes
import "internal/byteorder"
// Encrypt one block from src into dst, using the expanded key xk.
func encryptBlockGo(xk []uint32, dst, src []byte) {
_ = src[15] // early bounds check
s0 := byteorder.BeUint32(src[0:4])
s1 := byteorder.BeUint32(src[4:8])
s2 := byteorder.BeUint32(src[8:12])
s3 := byteorder.BeUint32(src[12:16])
// 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
var t0, t1, t2, t3 uint32
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[15] // early bounds check
byteorder.BePutUint32(dst[0:4], s0)
byteorder.BePutUint32(dst[4:8], s1)
byteorder.BePutUint32(dst[8:12], s2)
byteorder.BePutUint32(dst[12:16], s3)
}
// Decrypt one block from src into dst, using the expanded key xk.
func decryptBlockGo(xk []uint32, dst, src []byte) {
_ = src[15] // early bounds check
s0 := byteorder.BeUint32(src[0:4])
s1 := byteorder.BeUint32(src[4:8])
s2 := byteorder.BeUint32(src[8:12])
s3 := byteorder.BeUint32(src[12:16])
// 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
var t0, t1, t2, t3 uint32
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[15] // early bounds check
byteorder.BePutUint32(dst[0:4], s0)
byteorder.BePutUint32(dst[4:8], s1)
byteorder.BePutUint32(dst[8:12], s2)
byteorder.BePutUint32(dst[12:16], 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] = byteorder.BeUint32(key[4*i:])
}
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
}
}
}