201 lines
6.8 KiB
V
201 lines
6.8 KiB
V
// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
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// that can be found in the LICENSE file.
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// This implementation is derived from the golang implementation
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// which itself is derived in part from the reference
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// ANSI C implementation, which carries the following notice:
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//
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// rijndael-alg-fst.c
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//
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// @version 3.0 (December 2000)
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//
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// Optimised ANSI C code for the Rijndael cipher (now AES)
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//
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// @author Vincent Rijmen <vincent.rijmen@esat.kuleuven.ac.be>
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// @author Antoon Bosselaers <antoon.bosselaers@esat.kuleuven.ac.be>
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// @author Paulo Barreto <paulo.barreto@Terra.com.br>
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//
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// This code is hereby placed in the public domain.
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//
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// THIS SOFTWARE IS PROVIDED BY THE AUTHORS ''AS IS'' AND ANY EXPRESS
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// OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
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// OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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// EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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//
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// See FIPS 197 for specification, and see Daemen and Rijmen's Rijndael submission
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// for implementation details.
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// https://csrc.nist.gov/csrc/media/publications/fips/197/final/documents/fips-197.pdf
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// https://csrc.nist.gov/archive/aes/rijndael/Rijndael-ammended.pdf
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module aes
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import (
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encoding.binary
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)
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// Encrypt one block from src into dst, using the expanded key xk.
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fn encrypt_block_generic(xk []u32, dst, src []byte) {
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_ = src[15] // early bounds check
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mut s0 := binary.big_endian_u32(src[..4])
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mut s1 := binary.big_endian_u32(src.slice(4, 8))
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mut s2 := binary.big_endian_u32(src.slice(8, 12))
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mut s3 := binary.big_endian_u32(src.slice(12, 16))
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// First round just XORs input with key.
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s0 ^= xk[0]
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s1 ^= xk[1]
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s2 ^= xk[2]
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s3 ^= xk[3]
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// Middle rounds shuffle using tables.
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// Number of rounds is set by length of expanded key.
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nr := xk.len/4 - 2 // - 2: one above, one more below
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mut k := 4
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mut t0 := u32(0)
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mut t1 := u32(0)
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mut t2 := u32(0)
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mut t3 := u32(0)
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for r in 0..nr {
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t0 = xk[k+0] ^ te0[byte(s0>>24)] ^ te1[byte(s1>>16)] ^ te2[byte(s2>>8)] ^ u32(te3[byte(s3)])
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t1 = xk[k+1] ^ te0[byte(s1>>24)] ^ te1[byte(s2>>16)] ^ te2[byte(s3>>8)] ^ u32(te3[byte(s0)])
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t2 = xk[k+2] ^ te0[byte(s2>>24)] ^ te1[byte(s3>>16)] ^ te2[byte(s0>>8)] ^ u32(te3[byte(s1)])
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t3 = xk[k+3] ^ te0[byte(s3>>24)] ^ te1[byte(s0>>16)] ^ te2[byte(s1>>8)] ^ u32(te3[byte(s2)])
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k += 4
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s0 = t0
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s1 = t1
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s2 = t2
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s3 = t3
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}
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// Last round uses s-box directly and XORs to produce output.
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s0 = s_box0[t0>>24]<<24 | s_box0[t1>>16&0xff]<<16 | u32(s_box0[t2>>8&0xff]<<8) | s_box0[t3&u32(0xff)]
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s1 = s_box0[t1>>24]<<24 | s_box0[t2>>16&0xff]<<16 | u32(s_box0[t3>>8&0xff]<<8) | s_box0[t0&u32(0xff)]
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s2 = s_box0[t2>>24]<<24 | s_box0[t3>>16&0xff]<<16 | u32(s_box0[t0>>8&0xff]<<8) | s_box0[t1&u32(0xff)]
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s3 = s_box0[t3>>24]<<24 | s_box0[t0>>16&0xff]<<16 | u32(s_box0[t1>>8&0xff]<<8) | s_box0[t2&u32(0xff)]
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s0 ^= xk[k+0]
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s1 ^= xk[k+1]
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s2 ^= xk[k+2]
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s3 ^= xk[k+3]
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_ = dst[15] // early bounds check
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binary.big_endian_put_u32(mut dst[..4], s0)
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binary.big_endian_put_u32(mut dst.slice(4, 8), s1)
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binary.big_endian_put_u32(mut dst.slice(8, 12), s2)
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binary.big_endian_put_u32(mut dst.slice(12, 16), s3)
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}
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// Decrypt one block from src into dst, using the expanded key xk.
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fn decrypt_block_generic(xk []u32, dst, src []byte) {
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_ = src[15] // early bounds check
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mut s0 := binary.big_endian_u32(src[..4])
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mut s1 := binary.big_endian_u32(src.slice(4, 8))
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mut s2 := binary.big_endian_u32(src.slice(8, 12))
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mut s3 := binary.big_endian_u32(src.slice(12, 16))
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// First round just XORs input with key.
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s0 ^= xk[0]
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s1 ^= xk[1]
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s2 ^= xk[2]
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s3 ^= xk[3]
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// Middle rounds shuffle using tables.
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// Number of rounds is set by length of expanded key.
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nr := xk.len/4 - 2 // - 2: one above, one more below
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mut k := 4
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mut t0 := u32(0)
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mut t1 := u32(0)
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mut t2 := u32(0)
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mut t3 := u32(0)
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for r in 0..nr {
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t0 = xk[k+0] ^ td0[byte(s0>>24)] ^ td1[byte(s3>>16)] ^ td2[byte(s2>>8)] ^ u32(td3[byte(s1)])
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t1 = xk[k+1] ^ td0[byte(s1>>24)] ^ td1[byte(s0>>16)] ^ td2[byte(s3>>8)] ^ u32(td3[byte(s2)])
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t2 = xk[k+2] ^ td0[byte(s2>>24)] ^ td1[byte(s1>>16)] ^ td2[byte(s0>>8)] ^ u32(td3[byte(s3)])
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t3 = xk[k+3] ^ td0[byte(s3>>24)] ^ td1[byte(s2>>16)] ^ td2[byte(s1>>8)] ^ u32(td3[byte(s0)])
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k += 4
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s0 = t0
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s1 = t1
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s2 = t2
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s3 = t3
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}
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// Last round uses s-box directly and XORs to produce output.
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s0 = u32(s_box1[t0>>24])<<24 | u32(s_box1[t3>>16&0xff])<<16 | u32(s_box1[t2>>8&0xff]<<8) | u32(s_box1[t1&u32(0xff)])
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s1 = u32(s_box1[t1>>24])<<24 | u32(s_box1[t0>>16&0xff])<<16 | u32(s_box1[t3>>8&0xff]<<8) | u32(s_box1[t2&u32(0xff)])
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s2 = u32(s_box1[t2>>24])<<24 | u32(s_box1[t1>>16&0xff])<<16 | u32(s_box1[t0>>8&0xff]<<8) | u32(s_box1[t3&u32(0xff)])
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s3 = u32(s_box1[t3>>24])<<24 | u32(s_box1[t2>>16&0xff])<<16 | u32(s_box1[t1>>8&0xff]<<8) | u32(s_box1[t0&u32(0xff)])
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s0 ^= xk[k+0]
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s1 ^= xk[k+1]
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s2 ^= xk[k+2]
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s3 ^= xk[k+3]
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_ = dst[15] // early bounds check
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binary.big_endian_put_u32(mut dst[..4], s0)
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binary.big_endian_put_u32(mut dst.slice(4, 8), s1)
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binary.big_endian_put_u32(mut dst.slice(8, 12), s2)
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binary.big_endian_put_u32(mut dst.slice(12, 16), s3)
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}
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// Apply s_box0 to each byte in w.
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fn subw(w u32) u32 {
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return u32(s_box0[w>>24])<<24 |
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u32(s_box0[w>>16&0xff]<<16) |
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u32(s_box0[w>>8&0xff]<<8) |
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u32(s_box0[w&u32(0xff)])
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}
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// Rotate
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fn rotw(w u32) u32 { return (w<<8) | (w>>24) }
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// Key expansion algorithm. See FIPS-197, Figure 11.
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// Their rcon[i] is our powx[i-1] << 24.
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fn expand_key_generic(key []byte, enc mut []u32, dec mut []u32) {
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// Encryption key setup.
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mut i := 0
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nk := key.len / 4
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for i = 0; i < nk; i++ {
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if 4*i >= key.len {
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break
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}
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enc[i] = binary.big_endian_u32(key[4*i..])
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}
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for i < enc.len {
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mut t := enc[i-1]
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if i%nk == 0 {
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t = subw(rotw(t)) ^ u32(pow_x[i/nk-1]) << 24
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} else if nk > 6 && i%nk == 4 {
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t = subw(t)
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}
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enc[i] = enc[i-nk] ^ t
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i++
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}
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// Derive decryption key from encryption key.
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// Reverse the 4-word round key sets from enc to produce dec.
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// All sets but the first and last get the MixColumn transform applied.
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if dec.len == 0 {
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return
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}
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n := enc.len
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for i = 0; i < n; i += 4 {
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ei := n - i - 4
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for j in 0..4 {
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mut x := enc[ei+j]
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if i > 0 && i+4 < n {
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x = td0[s_box0[x>>24]] ^ td1[s_box0[x>>16&0xff]] ^ td2[s_box0[x>>8&0xff]] ^ td3[s_box0[x&u32(0xff)]]
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}
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dec[i+j] = x
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}
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}
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}
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