mirror of https://github.com/dirtbags/moth.git
54 lines
1.0 KiB
C
54 lines
1.0 KiB
C
#include <stdint.h>
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#include <stdlib.h>
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#include "arc4.h"
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#define swap(a, b) do {int _swap=a; a=b, b=_swap;} while (0)
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void
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arc4_init(struct arc4_ctx *ctx, uint8_t const *key, size_t keylen)
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{
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int i;
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int j = 0;
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for (i = 0; i < 256; i += 1) {
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ctx->S[i] = i;
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}
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for (i = 0; i < 256; i += 1) {
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j = (j + ctx->S[i] + key[i % keylen]) % 256;
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swap(ctx->S[i], ctx->S[j]);
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}
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ctx->i = 0;
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ctx->j = 0;
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}
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uint8_t
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arc4_pad(struct arc4_ctx *ctx)
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{
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ctx->i = (ctx->i + 1) % 256;
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ctx->j = (ctx->j + ctx->S[ctx->i]) % 256;
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swap(ctx->S[ctx->i], ctx->S[ctx->j]);
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return ctx->S[(ctx->S[ctx->i] + ctx->S[ctx->j]) % 256];
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}
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void
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arc4_crypt(struct arc4_ctx *ctx,
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uint8_t *obuf, uint8_t const *ibuf, size_t buflen)
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{
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size_t k;
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for (k = 0; k < buflen; k += 1) {
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obuf[k] = ibuf[k] ^ arc4_pad(ctx);
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}
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}
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void
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arc4_crypt_buffer(uint8_t const *key, size_t keylen,
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uint8_t *buf, size_t buflen)
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{
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struct arc4_ctx ctx;
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arc4_init(&ctx, key, keylen);
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arc4_crypt(&ctx, buf, buf, buflen);
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}
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