71 lines
1.9 KiB
C
71 lines
1.9 KiB
C
#include "aes_core.h"
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#include <assert.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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static void rk_init_ctr(struct ctr_state *state, const unsigned char *iv) {
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state->num = 0;
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memset(state->ecount, 0, 16);
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memcpy(state->ivec, iv, 16);
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}
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/* increment counter (128-bit int) by 1 */
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static void rk_ctr128_inc(unsigned char *counter) {
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unsigned int n = 16;
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unsigned char c;
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do {
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--n;
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c = counter[n];
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++c;
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counter[n] = c;
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if (c)
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return;
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} while (n);
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}
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static void rk_crypto_ctr128_encrypt(const unsigned char *in,
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unsigned char *out, int len,
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const void *key, unsigned char *ivec,
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unsigned char *ecount_buf,
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unsigned int *num) {
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int n, l = 0;
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n = *num;
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while (l < len) {
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if (n == 0) {
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rk_aes_encrypt(ivec, ecount_buf, key);
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rk_ctr128_inc(ivec);
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}
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out[l] = in[l] ^ ecount_buf[n];
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++l;
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n = (n + 1) % 16;
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}
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*num = n;
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}
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/* XTS makes use of two different keys, usually generated by splitting
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* the supplied block cipher's key in half.
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* Because of the splitting, users wanting AES 256 and AES 128 encryption
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* will need to choose key sizes of 512 bits and 256 bits respectively.
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*/
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int rk_aes_ctr_encrypt(const unsigned char *in, unsigned char *out,
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unsigned long length, const unsigned char *key,
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const int key_len, const unsigned char *ivec,
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const int enc) {
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RK_AES_KEY ks;
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struct ctr_state state;
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if (key_len != 16 && key_len != 24 && key_len != 32)
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return -1;
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rk_init_ctr(&state, ivec);
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rk_aes_set_encrypt_key(key, key_len * 8, &ks);
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rk_crypto_ctr128_encrypt(in, out, length, &ks, state.ivec, state.ecount,
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&state.num);
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return 0;
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}
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