54 lines
900 B
C
54 lines
900 B
C
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#include <stdint.h>
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#include "tests/arc4.h"
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/* Swap bytes. */
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static inline void
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swap_byte (uint8_t *a, uint8_t *b)
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{
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uint8_t t = *a;
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*a = *b;
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*b = t;
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}
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void
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arc4_init (struct arc4 *arc4, const void *key_, size_t size)
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{
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const uint8_t *key = key_;
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size_t key_idx;
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uint8_t *s;
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int i, j;
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s = arc4->s;
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arc4->i = arc4->j = 0;
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for (i = 0; i < 256; i++)
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s[i] = i;
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for (key_idx = 0, i = j = 0; i < 256; i++)
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{
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j = (j + s[i] + key[key_idx]) & 255;
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swap_byte (s + i, s + j);
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if (++key_idx >= size)
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key_idx = 0;
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}
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}
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void
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arc4_crypt (struct arc4 *arc4, void *buf_, size_t size)
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{
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uint8_t *buf = buf_;
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uint8_t *s;
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uint8_t i, j;
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s = arc4->s;
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i = arc4->i;
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j = arc4->j;
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while (size-- > 0)
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{
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i += 1;
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j += s[i];
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swap_byte (s + i, s + j);
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*buf++ ^= s[(s[i] + s[j]) & 255];
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}
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arc4->i = i;
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arc4->j = j;
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}
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