37 lines
887 B
C
37 lines
887 B
C
#include <string.h>
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#include "aes.h"
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#include "block.h"
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static uint8_t g_counter[16];
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void aes128_ctr_init(uint8_t *key, uint8_t *counter) {
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if (counter != NULL) {
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memcpy(g_counter, counter, 16);
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}
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if (key != NULL) {
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aes128_init(key);
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}
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}
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void aes128_ctr_evolve_counter(void) {
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block_incr(g_counter);
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return;
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}
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void aes128_ctr(uint8_t *dest, uint8_t *msg, uint32_t msg_len) {
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uint8_t buffer[16];
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uint32_t num_blocks = msg_len / 16;
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for (uint32_t i = 0; i < num_blocks; i++) {
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aes128_ecb(buffer, g_counter);
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aes128_ctr_evolve_counter();
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block_xor(dest + (i * 16), msg + (i * 16), buffer);
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}
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if (msg_len % 16) {
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aes128_ecb(buffer, g_counter);
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for (uint8_t i = 0; i < msg_len % 16; i++) {
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dest[num_blocks * 16 + i] = msg[num_blocks * 16 + i] ^ buffer[i];
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}
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}
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}
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