arcfour.c

[Valdas Andrulis]

On Tue, 10 Feb 1998, Yaroslav L. Halchinsky wrote:

> Dear All!
> Can anyone help me finding file `arcfour.c`?
> Thank you!
> 
> Yaroslav Halchinsky
> 


<<<<
<<<<<<arcfour.h>>>>>>
<<<<


/*

ARCFOUR cipher (based on a cipher posted on the Usenet in Spring-95).
This cipher is widely believed and has been tested to be equivalent
with the RC4 cipher from RSA Data Security, Inc.  (RC4 is a trademark
of RSA Data Security)

*/

/*
 * $Id: arcfour.h,v 1.1.1.1 1996/02/18 21:38:11 ylo Exp $
 * $Log: arcfour.h,v $
 * Revision 1.1.1.1  1996/02/18 21:38:11  ylo
 * 	Imported ssh-1.2.13.
 *
 * Revision 1.2  1995/07/13  01:30:25  ylo
 * 	Added cvs log.
 *
 * $Endlog$
 */

#ifndef ARCFOUR_H
#define ARCFOUR_H

typedef struct
{
   unsigned int x;
   unsigned int y;
   unsigned char state[256];
} ArcfourContext;

/* Initializes the context and sets the key. */
void arcfour_init(ArcfourContext *ctx, const unsigned char *key, 
		  unsigned int keylen);

/* Returns the next pseudo-random byte from the arcfour (pseudo-random 
   generator) stream. */
unsigned int arcfour_byte(ArcfourContext *ctx);

/* Encrypts data. */
void arcfour_encrypt(ArcfourContext *ctx, unsigned char *dest, 
		     const unsigned char *src, unsigned int len);

/* Decrypts data. */
void arcfour_decrypt(ArcfourContext *ctx, unsigned char *dest, 
		     const unsigned char *src, unsigned int len);

#endif /* ARCFOUR_H */

<<<<
<<<<<<arcfour.c>>>>>>
<<<<


/*

ARCFOUR cipher (based on a cipher posted on the Usenet in Spring-95).
This cipher is widely believed and has been tested to be equivalent
with the RC4 cipher from RSA Data Security, Inc.  (RC4 is a trademark
of RSA Data Security)

*/

/*
 * $Id: arcfour.c,v 1.1.1.1 1996/02/18 21:38:11 ylo Exp $
 * $Log: arcfour.c,v $
 * Revision 1.1.1.1  1996/02/18 21:38:11  ylo
 * 	Imported ssh-1.2.13.
 *
 * Revision 1.2  1995/07/13  01:29:59  ylo
 * 	Added cvs log.
 *
 * $Endlog$
 */

#include "assert.h"
#include "arcfour.h"

/* arcfour added for SAMBA-NTDOMAIN */

void arcfour(unsigned char data[16], unsigned char data_out[16], unsigned char data_in[16])
{
    ArcfourContext ctx1;
    
    arcfour_init(&ctx1, data, 16);
    arcfour_encrypt(&ctx1, data_out, data_in, 16);
}

void arcfour_init(ArcfourContext *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 arcfour_byte(ArcfourContext *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 arcfour_encrypt(ArcfourContext *ctx, unsigned char *dest, 
		     const unsigned char *src, unsigned int len)
{
  unsigned int i;
  for (i = 0; i < len; i++)
    dest[i] = src[i] ^ arcfour_byte(ctx);
}

void arcfour_decrypt(ArcfourContext *ctx, unsigned char *dest, 
		 const unsigned char *src, unsigned int len)
{
  arcfour_encrypt(ctx, dest, src, len);
}




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