44 lines
747 B
C
44 lines
747 B
C
/*
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* File: arcfour.c
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* Author: Daniel Otte
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* Date: 07.06.2006
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* License: GPL
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* Description: Implementation of the ARCFOUR (RC4 compatible) stream cipher algorithm.
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*
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*/
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#include <stdint.h>
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#include "arcfour.h"
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/*
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* length is length of key in bytes!
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*/
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void arcfour_init(arcfour_ctx_t *c, uint8_t *key, uint8_t length){
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uint8_t t;
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unsigned x,y=0;
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for(x=0; x<= 255; ++x)
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c->s[x]=x;
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for(x=0; x<= 255; ++x){
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y += c->s[x] + key[x % length];
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y &= 0xff;
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t = c->s[y];
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c->s[y] = c->s[x];
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c->s[x] = t;
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};
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c->i = c->j = 0;
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}
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uint8_t arcfour_gen(arcfour_ctx_t *c){
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uint8_t t;
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c->i++;
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c->j += c->s[c->i];
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t = c->s[c->j];
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c->s[c->j] = c->s[c->i];
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c->s[c->i] = t;
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return c->s[(c->s[c->j] + c->s[c->i]) & 0xff];
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}
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