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37 lines
751 B
C
37 lines
751 B
C
#include "aes-ctr.h"
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#include <string.h>
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#define AES_BLOCKLEN 16
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void aes_ctr_xcrypt_buffer(aes_context *ctx, const uint8_t *iv, uint8_t *buf, size_t length)
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{
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uint8_t bi, buffer[AES_BLOCKLEN], ivc[AES_BLOCKLEN];
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size_t i;
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memcpy(ivc,iv,AES_BLOCKLEN);
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for (i = 0, bi = AES_BLOCKLEN; i < length; ++i, ++bi)
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{
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if (bi == AES_BLOCKLEN) /* we need to regen xor compliment in buffer */
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{
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memcpy(buffer, ivc, AES_BLOCKLEN);
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aes_cipher(ctx, buffer, buffer);
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/* Increment ivc and handle overflow */
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for (bi = (AES_BLOCKLEN - 1); bi >= 0; --bi)
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{
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/* inc will owerflow */
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if (ivc[bi] == 255)
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{
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ivc[bi] = 0;
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continue;
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}
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ivc[bi] += 1;
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break;
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}
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bi = 0;
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}
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buf[i] = (buf[i] ^ buffer[bi]);
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}
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}
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