void inv_cipher(uint8_t *in, uint8_t *out, uint8_t *w) {
uint8_t state[4*Nb];
uint8_t r, i, j;
for (i = 0; i < 4; i++) {
for (j = 0; j < Nb; j++) {
state[Nb*i+j] = in[i+4*j];
}
}
add_round_key(state, w, Nr);
for (r = Nr-1; r >= 1; r--) {
inv_shift_rows(state);
inv_sub_bytes(state);
add_round_key(state, w, r);
inv_mix_columns(state);
}
inv_shift_rows(state);
inv_sub_bytes(state);
add_round_key(state, w, 0);
for (i = 0; i < 4; i++) {
for (j = 0; j < Nb; j++) {
out[i+4*j] = state[Nb*i+j];
}
}
}
void inv_cipher(uint8_t *in, uint8_t **key_schedule, uint8_t n_k, uint8_t n_r) {
uint8_t *state;
state = malloc(BLOCK_LENGTH_IN_BYTES * sizeof(uint8_t));
if(state == NULL) {
printf("malloc returned NULL in inv_cipher");
exit(1);
}
memcpy(state, in, BLOCK_LENGTH_IN_BYTES * sizeof(uint8_t));
if (DEBUG) {
printf("\nRound 0\n");
debug_print_block(state, " Start: ");
}
add_round_key(state, key_schedule, n_r);
if (DEBUG) {
debug_print_key_schedule(key_schedule, n_r);
}
for (int rnd = 1; rnd < n_r; rnd++) {
if (DEBUG) printf("\n\nRound %2d\n", rnd);
debug_print_block(state, " Start: ");
inv_shift_rows(state);
debug_print_block(state, " Shift: ");
inv_sub_bytes(state);
debug_print_block(state, " Subst: ");
add_round_key(state, key_schedule, n_r - rnd);
inv_mix_columns(state);
debug_print_block(state, " Mxcol: ");
debug_print_key_schedule(key_schedule, rnd);
}
if (DEBUG) printf("\n\nRound 10\n");
debug_print_block(state, " Start: ");
inv_shift_rows(state);
debug_print_block(state, " Shift: ");
inv_sub_bytes(state);
debug_print_block(state, " Subst: ");
add_round_key(state, key_schedule, 0);
debug_print_key_schedule(key_schedule, 10);
debug_print_block(state, "\n\nPLAINTEXT\n");
}
void aes_decrypt(aes_ctx *ctx, const byte *in, byte *out)
{
int i;
byte state[16];
memcpy(state, in, 16);
add_round_key(state, ctx->sub_key);
for (i = 1; i < 10; i++) {
inv_shift_rows(state);
inv_sub_bytes(state);
add_round_key(state, ctx->sub_key + (i * 16));
inv_mix_columns(state);
}
inv_shift_rows(state);
inv_sub_bytes(state);
add_round_key(state, ctx->sub_key + (i * 16));
memcpy(out, state, 16);
}
void test_inv_mix_columns()
{
uint8_t state[16] = {
0x47,0x37,0x94,0xED,
0x40,0xD4,0xE4,0xA5,
0xA3,0x70,0x3A,0xA6,
0x4C,0x9F,0x42,0xBC
};
uint8_t ret_state[16] = {
0x87,0x6E,0x46,0xA6,
0xF2,0x4C,0xE7,0x8C,
0x4D,0x90,0x4A,0xD8,
0x97,0xEC,0xC3,0x95
};
inv_mix_columns(state);
int ret = memcmp(ret_state, state, sizeof(ret_state));
CU_ASSERT_EQUAL(ret, 0);
}
void aes128_ecb_decrypt(uint8_t *plaintext, const uint8_t *key, const uint8_t *ciphertext) {
int round;
memcpy(plaintext, ciphertext, 16);
key_schedule(key, round_keys);
add_round_key(plaintext, round_keys + 160);
inv_shift_rows(plaintext);
inv_sub_bytes(plaintext);
for (round = N_ROUNDS - 1; round > 0; round--) {
add_round_key(plaintext, round_keys + 16 * round);
inv_mix_columns(plaintext);
inv_shift_rows(plaintext);
inv_sub_bytes(plaintext);
}
add_round_key(plaintext, round_keys);
}
void test_mix_columns(){
unsigned char block[] = {0x87, 0x6e, 0x46, 0xa6,
0xf2, 0x4c, 0xe7, 0x8c,
0x4d, 0x90, 0x4a, 0xd8,
0x97, 0xec, 0xc3, 0x95, 0x00},
origblock[17];
unsigned char expected[] = {0x47, 0x37, 0x94, 0xed,
0x40, 0xd4, 0xe4, 0xa5,
0xa3, 0x70, 0x3a, 0xa6,
0x4c, 0x9f, 0x42, 0xbc, 0x00};
memcpy(origblock, block, 17);
mix_columns(block, 16);
print_block(block, 16);
printf("\n");
print_block(expected, 16);
printf("\n");
assert( bytencmp(block, expected, 16) == 0 );
inv_mix_columns(block, 16);
assert( bytencmp(block, origblock, 16) == 0);
print_block(block, 16);
printf("\n");
}
