diff options
Diffstat (limited to 'third_party/bearssl/src/aes_ct_dec.c')
| -rw-r--r-- | third_party/bearssl/src/aes_ct_dec.c | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/third_party/bearssl/src/aes_ct_dec.c b/third_party/bearssl/src/aes_ct_dec.c new file mode 100644 index 0000000..7f32d2b --- /dev/null +++ b/third_party/bearssl/src/aes_ct_dec.c @@ -0,0 +1,170 @@ +/* + * Copyright (c) 2016 Thomas Pornin <[email protected]> + * + * Permission is hereby granted, free of charge, to any person obtaining + * a copy of this software and associated documentation files (the + * "Software"), to deal in the Software without restriction, including + * without limitation the rights to use, copy, modify, merge, publish, + * distribute, sublicense, and/or sell copies of the Software, and to + * permit persons to whom the Software is furnished to do so, subject to + * the following conditions: + * + * The above copyright notice and this permission notice shall be + * included in all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, + * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF + * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND + * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS + * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN + * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN + * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE + * SOFTWARE. + */ + +#include "inner.h" + +/* see inner.h */ +void +br_aes_ct_bitslice_invSbox(uint32_t *q) +{ + /* + * AES S-box is: + * S(x) = A(I(x)) ^ 0x63 + * where I() is inversion in GF(256), and A() is a linear + * transform (0 is formally defined to be its own inverse). + * Since inversion is an involution, the inverse S-box can be + * computed from the S-box as: + * iS(x) = B(S(B(x ^ 0x63)) ^ 0x63) + * where B() is the inverse of A(). Indeed, for any y in GF(256): + * iS(S(y)) = B(A(I(B(A(I(y)) ^ 0x63 ^ 0x63))) ^ 0x63 ^ 0x63) = y + * + * Note: we reuse the implementation of the forward S-box, + * instead of duplicating it here, so that total code size is + * lower. By merging the B() transforms into the S-box circuit + * we could make faster CBC decryption, but CBC decryption is + * already quite faster than CBC encryption because we can + * process two blocks in parallel. + */ + uint32_t q0, q1, q2, q3, q4, q5, q6, q7; + + q0 = ~q[0]; + q1 = ~q[1]; + q2 = q[2]; + q3 = q[3]; + q4 = q[4]; + q5 = ~q[5]; + q6 = ~q[6]; + q7 = q[7]; + q[7] = q1 ^ q4 ^ q6; + q[6] = q0 ^ q3 ^ q5; + q[5] = q7 ^ q2 ^ q4; + q[4] = q6 ^ q1 ^ q3; + q[3] = q5 ^ q0 ^ q2; + q[2] = q4 ^ q7 ^ q1; + q[1] = q3 ^ q6 ^ q0; + q[0] = q2 ^ q5 ^ q7; + + br_aes_ct_bitslice_Sbox(q); + + q0 = ~q[0]; + q1 = ~q[1]; + q2 = q[2]; + q3 = q[3]; + q4 = q[4]; + q5 = ~q[5]; + q6 = ~q[6]; + q7 = q[7]; + q[7] = q1 ^ q4 ^ q6; + q[6] = q0 ^ q3 ^ q5; + q[5] = q7 ^ q2 ^ q4; + q[4] = q6 ^ q1 ^ q3; + q[3] = q5 ^ q0 ^ q2; + q[2] = q4 ^ q7 ^ q1; + q[1] = q3 ^ q6 ^ q0; + q[0] = q2 ^ q5 ^ q7; +} + +static void +add_round_key(uint32_t *q, const uint32_t *sk) +{ + int i; + + for (i = 0; i < 8; i ++) { + q[i] ^= sk[i]; + } +} + +static void +inv_shift_rows(uint32_t *q) +{ + int i; + + for (i = 0; i < 8; i ++) { + uint32_t x; + + x = q[i]; + q[i] = (x & 0x000000FF) + | ((x & 0x00003F00) << 2) | ((x & 0x0000C000) >> 6) + | ((x & 0x000F0000) << 4) | ((x & 0x00F00000) >> 4) + | ((x & 0x03000000) << 6) | ((x & 0xFC000000) >> 2); + } +} + +static inline uint32_t +rotr16(uint32_t x) +{ + return (x << 16) | (x >> 16); +} + +static void +inv_mix_columns(uint32_t *q) +{ + uint32_t q0, q1, q2, q3, q4, q5, q6, q7; + uint32_t r0, r1, r2, r3, r4, r5, r6, r7; + + q0 = q[0]; + q1 = q[1]; + q2 = q[2]; + q3 = q[3]; + q4 = q[4]; + q5 = q[5]; + q6 = q[6]; + q7 = q[7]; + r0 = (q0 >> 8) | (q0 << 24); + r1 = (q1 >> 8) | (q1 << 24); + r2 = (q2 >> 8) | (q2 << 24); + r3 = (q3 >> 8) | (q3 << 24); + r4 = (q4 >> 8) | (q4 << 24); + r5 = (q5 >> 8) | (q5 << 24); + r6 = (q6 >> 8) | (q6 << 24); + r7 = (q7 >> 8) | (q7 << 24); + + q[0] = q5 ^ q6 ^ q7 ^ r0 ^ r5 ^ r7 ^ rotr16(q0 ^ q5 ^ q6 ^ r0 ^ r5); + q[1] = q0 ^ q5 ^ r0 ^ r1 ^ r5 ^ r6 ^ r7 ^ rotr16(q1 ^ q5 ^ q7 ^ r1 ^ r5 ^ r6); + q[2] = q0 ^ q1 ^ q6 ^ r1 ^ r2 ^ r6 ^ r7 ^ rotr16(q0 ^ q2 ^ q6 ^ r2 ^ r6 ^ r7); + q[3] = q0 ^ q1 ^ q2 ^ q5 ^ q6 ^ r0 ^ r2 ^ r3 ^ r5 ^ rotr16(q0 ^ q1 ^ q3 ^ q5 ^ q6 ^ q7 ^ r0 ^ r3 ^ r5 ^ r7); + q[4] = q1 ^ q2 ^ q3 ^ q5 ^ r1 ^ r3 ^ r4 ^ r5 ^ r6 ^ r7 ^ rotr16(q1 ^ q2 ^ q4 ^ q5 ^ q7 ^ r1 ^ r4 ^ r5 ^ r6); + q[5] = q2 ^ q3 ^ q4 ^ q6 ^ r2 ^ r4 ^ r5 ^ r6 ^ r7 ^ rotr16(q2 ^ q3 ^ q5 ^ q6 ^ r2 ^ r5 ^ r6 ^ r7); + q[6] = q3 ^ q4 ^ q5 ^ q7 ^ r3 ^ r5 ^ r6 ^ r7 ^ rotr16(q3 ^ q4 ^ q6 ^ q7 ^ r3 ^ r6 ^ r7); + q[7] = q4 ^ q5 ^ q6 ^ r4 ^ r6 ^ r7 ^ rotr16(q4 ^ q5 ^ q7 ^ r4 ^ r7); +} + +/* see inner.h */ +void +br_aes_ct_bitslice_decrypt(unsigned num_rounds, + const uint32_t *skey, uint32_t *q) +{ + unsigned u; + + add_round_key(q, skey + (num_rounds << 3)); + for (u = num_rounds - 1; u > 0; u --) { + inv_shift_rows(q); + br_aes_ct_bitslice_invSbox(q); + add_round_key(q, skey + (u << 3)); + inv_mix_columns(q); + } + inv_shift_rows(q); + br_aes_ct_bitslice_invSbox(q); + add_round_key(q, skey); +} |