2 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files (the
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10 * the following conditions:
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
29 br_aes_ct_bitslice_invSbox(uint32_t *q)
33 * S(x) = A(I(x)) ^ 0x63
34 * where I() is inversion in GF(256), and A() is a linear
35 * transform (0 is formally defined to be its own inverse).
36 * Since inversion is an involution, the inverse S-box can be
37 * computed from the S-box as:
38 * iS(x) = B(S(B(x ^ 0x63)) ^ 0x63)
39 * where B() is the inverse of A(). Indeed, for any y in GF(256):
40 * iS(S(y)) = B(A(I(B(A(I(y)) ^ 0x63 ^ 0x63))) ^ 0x63 ^ 0x63) = y
42 * Note: we reuse the implementation of the forward S-box,
43 * instead of duplicating it here, so that total code size is
44 * lower. By merging the B() transforms into the S-box circuit
45 * we could make faster CBC decryption, but CBC decryption is
46 * already quite faster than CBC encryption because we can
47 * process two blocks in parallel.
49 uint32_t q0, q1, q2, q3, q4, q5, q6, q7;
68 br_aes_ct_bitslice_Sbox(q);
89 add_round_key(uint32_t *q, const uint32_t *sk)
93 for (i = 0; i < 8; i ++) {
99 inv_shift_rows(uint32_t *q)
103 for (i = 0; i < 8; i ++) {
107 q[i] = (x & 0x000000FF)
108 | ((x & 0x00003F00) << 2) | ((x & 0x0000C000) >> 6)
109 | ((x & 0x000F0000) << 4) | ((x & 0x00F00000) >> 4)
110 | ((x & 0x03000000) << 6) | ((x & 0xFC000000) >> 2);
114 static inline uint32_t
117 return (x << 16) | (x >> 16);
121 inv_mix_columns(uint32_t *q)
123 uint32_t q0, q1, q2, q3, q4, q5, q6, q7;
124 uint32_t r0, r1, r2, r3, r4, r5, r6, r7;
134 r0 = (q0 >> 8) | (q0 << 24);
135 r1 = (q1 >> 8) | (q1 << 24);
136 r2 = (q2 >> 8) | (q2 << 24);
137 r3 = (q3 >> 8) | (q3 << 24);
138 r4 = (q4 >> 8) | (q4 << 24);
139 r5 = (q5 >> 8) | (q5 << 24);
140 r6 = (q6 >> 8) | (q6 << 24);
141 r7 = (q7 >> 8) | (q7 << 24);
143 q[0] = q5 ^ q6 ^ q7 ^ r0 ^ r5 ^ r7 ^ rotr16(q0 ^ q5 ^ q6 ^ r0 ^ r5);
144 q[1] = q0 ^ q5 ^ r0 ^ r1 ^ r5 ^ r6 ^ r7 ^ rotr16(q1 ^ q5 ^ q7 ^ r1 ^ r5 ^ r6);
145 q[2] = q0 ^ q1 ^ q6 ^ r1 ^ r2 ^ r6 ^ r7 ^ rotr16(q0 ^ q2 ^ q6 ^ r2 ^ r6 ^ r7);
146 q[3] = q0 ^ q1 ^ q2 ^ q5 ^ q6 ^ r0 ^ r2 ^ r3 ^ r5 ^ rotr16(q0 ^ q1 ^ q3 ^ q5 ^ q6 ^ q7 ^ r0 ^ r3 ^ r5 ^ r7);
147 q[4] = q1 ^ q2 ^ q3 ^ q5 ^ r1 ^ r3 ^ r4 ^ r5 ^ r6 ^ r7 ^ rotr16(q1 ^ q2 ^ q4 ^ q5 ^ q7 ^ r1 ^ r4 ^ r5 ^ r6);
148 q[5] = q2 ^ q3 ^ q4 ^ q6 ^ r2 ^ r4 ^ r5 ^ r6 ^ r7 ^ rotr16(q2 ^ q3 ^ q5 ^ q6 ^ r2 ^ r5 ^ r6 ^ r7);
149 q[6] = q3 ^ q4 ^ q5 ^ q7 ^ r3 ^ r5 ^ r6 ^ r7 ^ rotr16(q3 ^ q4 ^ q6 ^ q7 ^ r3 ^ r6 ^ r7);
150 q[7] = q4 ^ q5 ^ q6 ^ r4 ^ r6 ^ r7 ^ rotr16(q4 ^ q5 ^ q7 ^ r4 ^ r7);
155 br_aes_ct_bitslice_decrypt(unsigned num_rounds,
156 const uint32_t *skey, uint32_t *q)
160 add_round_key(q, skey + (num_rounds << 3));
161 for (u = num_rounds - 1; u > 0; u --) {
163 br_aes_ct_bitslice_invSbox(q);
164 add_round_key(q, skey + (u << 3));
168 br_aes_ct_bitslice_invSbox(q);
169 add_round_key(q, skey);