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/*
Alleged RC4 (based on the Usenet posting in Spring-95)
*/
#include "includes.h"
RCSID("$Id: rc4.c,v 1.1 1999/09/26 20:53:37 deraadt Exp $");
#include "rc4.h"
void rc4_init(RC4Context *ctx, const unsigned char *key, unsigned int key_len)
{
unsigned int t, u;
unsigned int keyindex;
unsigned int stateindex;
unsigned char* state;
unsigned int counter;
assert(key_len > 0);
state = &ctx->state[0];
ctx->x = 0;
ctx->y = 0;
for (counter = 0; counter < 256; counter++)
state[counter] = counter;
keyindex = 0;
stateindex = 0;
for (counter = 0; counter < 256; counter++)
{
t = state[counter];
stateindex = (stateindex + key[keyindex] + t) & 0xff;
u = state[stateindex];
state[stateindex] = t;
state[counter] = u;
if (++keyindex >= key_len)
keyindex = 0;
}
}
inline unsigned int rc4_byte(RC4Context *ctx)
{
unsigned int x;
unsigned int y;
unsigned int sx, sy;
unsigned char *state;
state = ctx->state;
x = (ctx->x + 1) & 0xff;
sx = state[x];
y = (sx + ctx->y) & 0xff;
sy = state[y];
ctx->x = x;
ctx->y = y;
state[y] = sx;
state[x] = sy;
return state[(sx + sy) & 0xff];
}
void rc4_encrypt(RC4Context *ctx, unsigned char *dest,
const unsigned char *src, unsigned int len)
{
unsigned int i;
for (i = 0; i < len; i++)
dest[i] = src[i] ^ rc4_byte(ctx);
}
void rc4_decrypt(RC4Context *ctx, unsigned char *dest,
const unsigned char *src, unsigned int len)
{
rc4_encrypt(ctx, dest, src, len);
}
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