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/* aes_decrypt.c - TinyCrypt implementation of AES decryption procedure */
/*
* Copyright (C) 2015 by Intel Corporation, All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Intel Corporation nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* aes_decrypt.c -- An implementation of AES decryption procedure.
*
* See the corresponding header file for more information.
*
*/
#include "aes.h"
#include "utils.h"
static const uint8_t inv_sbox[256] = {
0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e,
0x81, 0xf3, 0xd7, 0xfb, 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87,
0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb, 0x54, 0x7b, 0x94, 0x32,
0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49,
0x6d, 0x8b, 0xd1, 0x25, 0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16,
0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92, 0x6c, 0x70, 0x48, 0x50,
0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05,
0xb8, 0xb3, 0x45, 0x06, 0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02,
0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, 0x3a, 0x91, 0x11, 0x41,
0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8,
0x1c, 0x75, 0xdf, 0x6e, 0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89,
0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, 0xfc, 0x56, 0x3e, 0x4b,
0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59,
0x27, 0x80, 0xec, 0x5f, 0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d,
0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, 0xa0, 0xe0, 0x3b, 0x4d,
0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63,
0x55, 0x21, 0x0c, 0x7d
};
int32_t aes128_set_decrypt_key (
AesKeySched_t s, const uint8_t *k) {
return aes128_set_encrypt_key (s, k);
}
#define mult8(a) (double_byte (double_byte (double_byte (a))))
#define mult9(a) (mult8(a)^(a))
#define multb(a) (mult8(a)^double_byte(a)^(a))
#define multd(a) (mult8(a)^double_byte(double_byte(a))^(a))
#define multe(a) (mult8(a)^double_byte(double_byte(a))^double_byte(a))
static inline void mult_row_column (
uint8_t *out, const uint8_t *in) {
out[0] = multe (in[0]) ^ multb (in[1]) ^ multd (in[2]) ^ mult9 (in[3]);
out[1] = mult9 (in[0]) ^ multe (in[1]) ^ multb (in[2]) ^ multd (in[3]);
out[2] = multd (in[0]) ^ mult9 (in[1]) ^ multe (in[2]) ^ multb (in[3]);
out[3] = multb (in[0]) ^ multd (in[1]) ^ mult9 (in[2]) ^ multe (in[3]);
}
static inline void inv_mix_columns (uint8_t *s) {
uint8_t t[Nb*Nk];
mult_row_column (t, s);
mult_row_column (&t[Nb], s+Nb);
mult_row_column (&t[2*Nb], s+(2*Nb));
mult_row_column (&t[3*Nb], s+(3*Nb));
(void) copy (s, sizeof (t), t, sizeof (t));
}
static inline void add_round_key (uint8_t *s, const uint32_t *k) {
s[ 0] ^= (uint8_t)(k[0]>>24); s[ 1] ^= (uint8_t)(k[0]>>16);
s[ 2] ^= (uint8_t)(k[0]>> 8); s[ 3] ^= (uint8_t)(k[0]);
s[ 4] ^= (uint8_t)(k[1]>>24); s[ 5] ^= (uint8_t)(k[1]>>16);
s[ 6] ^= (uint8_t)(k[1]>> 8); s[ 7] ^= (uint8_t)(k[1]);
s[ 8] ^= (uint8_t)(k[2]>>24); s[ 9] ^= (uint8_t)(k[2]>>16);
s[10] ^= (uint8_t)(k[2]>> 8); s[11] ^= (uint8_t)(k[2]);
s[12] ^= (uint8_t)(k[3]>>24); s[13] ^= (uint8_t)(k[3]>>16);
s[14] ^= (uint8_t)(k[3]>> 8); s[15] ^= (uint8_t)(k[3]);
}
static inline void inv_sub_bytes (uint8_t *s) {
uint32_t i;
for (i = 0; i < (Nb*Nk); ++i) {
s[i] = inv_sbox[s[i]];
}
}
/*
* This inv_shift_rows also implements the matrix flip required for
* inv_mix_columns, but performs it here to reduce the number of memory
* operations.
*/
static inline void inv_shift_rows (uint8_t *s) {
uint8_t t[Nb*Nk];
t[0] = s[ 0]; t[ 1] = s[13]; t[ 2] = s[10]; t[ 3] = s[ 7];
t[4] = s[ 4]; t[ 5] = s[ 1]; t[ 6] = s[14]; t[ 7] = s[11];
t[8] = s[ 8]; t[ 9] = s[ 5]; t[10] = s[ 2]; t[11] = s[15];
t[12] = s[12]; t[13] = s[ 9]; t[14] = s[ 6]; t[15] = s[ 3];
(void) copy (s, sizeof (t), t, sizeof (t));
}
int32_t aes_decrypt (
uint8_t *out, const uint8_t *in, const AesKeySched_t s) {
uint8_t state[Nk*Nb];
uint32_t i;
if (out == (uint8_t *) 0) {
return 0;
} else if (in == (const uint8_t *) 0) {
return 0;
} else if (s == (AesKeySched_t) 0) {
return 0;
}
(void) copy (state, sizeof (state), in, sizeof (state));
add_round_key (state, s->words + Nb*Nr);
for (i = Nr-1; i > 0; --i) {
inv_shift_rows (state);
inv_sub_bytes (state);
add_round_key (state, s->words + Nb*i);
inv_mix_columns (state);
}
inv_shift_rows (state);
inv_sub_bytes (state);
add_round_key (state, s->words);
(void) copy (out, sizeof (state), state, sizeof (state));
set (state, 0x00, sizeof (state));
return 1;
}
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