171 lines
4.6 KiB
C
171 lines
4.6 KiB
C
/*
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* Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#include "inner.h"
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/* see inner.h */
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void
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br_aes_ct_bitslice_invSbox(uint32_t *q)
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{
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/*
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* AES S-box is:
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* S(x) = A(I(x)) ^ 0x63
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* where I() is inversion in GF(256), and A() is a linear
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* transform (0 is formally defined to be its own inverse).
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* Since inversion is an involution, the inverse S-box can be
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* computed from the S-box as:
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* iS(x) = B(S(B(x ^ 0x63)) ^ 0x63)
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* where B() is the inverse of A(). Indeed, for any y in GF(256):
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* iS(S(y)) = B(A(I(B(A(I(y)) ^ 0x63 ^ 0x63))) ^ 0x63 ^ 0x63) = y
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*
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* Note: we reuse the implementation of the forward S-box,
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* instead of duplicating it here, so that total code size is
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* lower. By merging the B() transforms into the S-box circuit
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* we could make faster CBC decryption, but CBC decryption is
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* already quite faster than CBC encryption because we can
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* process two blocks in parallel.
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*/
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uint32_t q0, q1, q2, q3, q4, q5, q6, q7;
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q0 = ~q[0];
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q1 = ~q[1];
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q2 = q[2];
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q3 = q[3];
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q4 = q[4];
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q5 = ~q[5];
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q6 = ~q[6];
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q7 = q[7];
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q[7] = q1 ^ q4 ^ q6;
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q[6] = q0 ^ q3 ^ q5;
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q[5] = q7 ^ q2 ^ q4;
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q[4] = q6 ^ q1 ^ q3;
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q[3] = q5 ^ q0 ^ q2;
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q[2] = q4 ^ q7 ^ q1;
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q[1] = q3 ^ q6 ^ q0;
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q[0] = q2 ^ q5 ^ q7;
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br_aes_ct_bitslice_Sbox(q);
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q0 = ~q[0];
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q1 = ~q[1];
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q2 = q[2];
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q3 = q[3];
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q4 = q[4];
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q5 = ~q[5];
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q6 = ~q[6];
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q7 = q[7];
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q[7] = q1 ^ q4 ^ q6;
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q[6] = q0 ^ q3 ^ q5;
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q[5] = q7 ^ q2 ^ q4;
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q[4] = q6 ^ q1 ^ q3;
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q[3] = q5 ^ q0 ^ q2;
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q[2] = q4 ^ q7 ^ q1;
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q[1] = q3 ^ q6 ^ q0;
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q[0] = q2 ^ q5 ^ q7;
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}
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static void
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add_round_key(uint32_t *q, const uint32_t *sk)
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{
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int i;
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for (i = 0; i < 8; i ++) {
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q[i] ^= sk[i];
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}
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}
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static void
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inv_shift_rows(uint32_t *q)
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{
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int i;
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for (i = 0; i < 8; i ++) {
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uint32_t x;
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x = q[i];
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q[i] = (x & 0x000000FF)
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| ((x & 0x00003F00) << 2) | ((x & 0x0000C000) >> 6)
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| ((x & 0x000F0000) << 4) | ((x & 0x00F00000) >> 4)
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| ((x & 0x03000000) << 6) | ((x & 0xFC000000) >> 2);
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}
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}
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static inline uint32_t
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rotr16(uint32_t x)
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{
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return (x << 16) | (x >> 16);
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}
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static void
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inv_mix_columns(uint32_t *q)
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{
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uint32_t q0, q1, q2, q3, q4, q5, q6, q7;
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uint32_t r0, r1, r2, r3, r4, r5, r6, r7;
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q0 = q[0];
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q1 = q[1];
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q2 = q[2];
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q3 = q[3];
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q4 = q[4];
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q5 = q[5];
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q6 = q[6];
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q7 = q[7];
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r0 = (q0 >> 8) | (q0 << 24);
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r1 = (q1 >> 8) | (q1 << 24);
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r2 = (q2 >> 8) | (q2 << 24);
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r3 = (q3 >> 8) | (q3 << 24);
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r4 = (q4 >> 8) | (q4 << 24);
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r5 = (q5 >> 8) | (q5 << 24);
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r6 = (q6 >> 8) | (q6 << 24);
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r7 = (q7 >> 8) | (q7 << 24);
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q[0] = q5 ^ q6 ^ q7 ^ r0 ^ r5 ^ r7 ^ rotr16(q0 ^ q5 ^ q6 ^ r0 ^ r5);
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q[1] = q0 ^ q5 ^ r0 ^ r1 ^ r5 ^ r6 ^ r7 ^ rotr16(q1 ^ q5 ^ q7 ^ r1 ^ r5 ^ r6);
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q[2] = q0 ^ q1 ^ q6 ^ r1 ^ r2 ^ r6 ^ r7 ^ rotr16(q0 ^ q2 ^ q6 ^ r2 ^ r6 ^ r7);
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q[3] = q0 ^ q1 ^ q2 ^ q5 ^ q6 ^ r0 ^ r2 ^ r3 ^ r5 ^ rotr16(q0 ^ q1 ^ q3 ^ q5 ^ q6 ^ q7 ^ r0 ^ r3 ^ r5 ^ r7);
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q[4] = q1 ^ q2 ^ q3 ^ q5 ^ r1 ^ r3 ^ r4 ^ r5 ^ r6 ^ r7 ^ rotr16(q1 ^ q2 ^ q4 ^ q5 ^ q7 ^ r1 ^ r4 ^ r5 ^ r6);
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q[5] = q2 ^ q3 ^ q4 ^ q6 ^ r2 ^ r4 ^ r5 ^ r6 ^ r7 ^ rotr16(q2 ^ q3 ^ q5 ^ q6 ^ r2 ^ r5 ^ r6 ^ r7);
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q[6] = q3 ^ q4 ^ q5 ^ q7 ^ r3 ^ r5 ^ r6 ^ r7 ^ rotr16(q3 ^ q4 ^ q6 ^ q7 ^ r3 ^ r6 ^ r7);
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q[7] = q4 ^ q5 ^ q6 ^ r4 ^ r6 ^ r7 ^ rotr16(q4 ^ q5 ^ q7 ^ r4 ^ r7);
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}
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/* see inner.h */
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void
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br_aes_ct_bitslice_decrypt(unsigned num_rounds,
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const uint32_t *skey, uint32_t *q)
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{
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unsigned u;
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add_round_key(q, skey + (num_rounds << 3));
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for (u = num_rounds - 1; u > 0; u --) {
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inv_shift_rows(q);
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br_aes_ct_bitslice_invSbox(q);
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add_round_key(q, skey + (u << 3));
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inv_mix_columns(q);
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}
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inv_shift_rows(q);
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br_aes_ct_bitslice_invSbox(q);
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add_round_key(q, skey);
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}
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