mirror of https://github.com/kokke/tiny-AES-c
adding CTR-mode
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41
aes.c
41
aes.c
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@ -1,6 +1,6 @@
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/*
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This is an implementation of the AES algorithm, specifically ECB and CBC mode.
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This is an implementation of the AES algorithm, specifically ECB, CTR and CBC mode.
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Block size can be chosen in aes.h - available choices are AES128, AES192, AES256.
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The implementation is verified against the test vectors in:
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@ -595,3 +595,42 @@ void AES_CBC_decrypt_buffer(uint8_t* output, uint8_t* input, uint32_t length, co
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}
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#endif // #if defined(CBC) && (CBC == 1)
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#if defined(CTR) && (CTR == 1)
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void AES_CTR_xcrypt_buffer(uint8_t* output, uint8_t* input, uint32_t length, const uint8_t* key, const uint8_t* iv)
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{
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uint8_t buffer[BLOCKLEN], counter[BLOCKLEN];
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memcpy(counter, iv, BLOCKLEN);
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Key = key;
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KeyExpansion();
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int i, j;
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for (i = 0; i < length; ++i)
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{
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if ((i & 0x0F) == 0)
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{
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memcpy(buffer, counter, BLOCKLEN);
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state = (state_t *) buffer;
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Cipher();
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for (j = (BLOCKLEN - 1); j >= 0; --j)
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{
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counter[j] += 1;
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if (counter[j] != 0)
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{
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break;
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}
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}
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}
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output[i] = (input[i]) ^ (buffer[i & 0x0F]);
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}
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}
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#endif // #if defined(CTR) && (CTR == 1)
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