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
6 * "Software"), to deal in the Software without restriction, including
7 * without limitation the rights to use, copy, modify, merge, publish,
8 * distribute, sublicense, and/or sell copies of the Software, and to
9 * permit persons to whom the Software is furnished to do so, subject to
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,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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
);