The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/crypto/rc4/rc4.c

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    1 
    2 /*
    3  * rc4.c
    4  *
    5  * Copyright (c) 1996-2000 Whistle Communications, Inc.
    6  * All rights reserved.
    7  * 
    8  * Subject to the following obligations and disclaimer of warranty, use and
    9  * redistribution of this software, in source or object code forms, with or
   10  * without modifications are expressly permitted by Whistle Communications;
   11  * provided, however, that:
   12  * 1. Any and all reproductions of the source or object code must include the
   13  *    copyright notice above and the following disclaimer of warranties; and
   14  * 2. No rights are granted, in any manner or form, to use Whistle
   15  *    Communications, Inc. trademarks, including the mark "WHISTLE
   16  *    COMMUNICATIONS" on advertising, endorsements, or otherwise except as
   17  *    such appears in the above copyright notice or in the software.
   18  * 
   19  * THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
   20  * TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
   21  * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
   22  * INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
   23  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
   24  * WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
   25  * REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
   26  * SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
   27  * IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
   28  * RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
   29  * WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
   30  * PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
   31  * SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY
   32  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   33  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   34  * THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
   35  * OF SUCH DAMAGE.
   36  *
   37  * $FreeBSD: releng/5.0/sys/crypto/rc4/rc4.c 63249 2000-07-16 05:53:14Z peter $
   38  */
   39 
   40 #include <sys/types.h>
   41 #include <crypto/rc4/rc4.h>
   42 
   43 static __inline void
   44 swap_bytes(u_char *a, u_char *b)
   45 {
   46         u_char temp;
   47 
   48         temp = *a;
   49         *a = *b;
   50         *b = temp;
   51 }
   52 
   53 /*
   54  * Initialize an RC4 state buffer using the supplied key,
   55  * which can have arbitrary length.
   56  */
   57 void
   58 rc4_init(struct rc4_state *const state, const u_char *key, int keylen)
   59 {
   60         u_char j;
   61         int i;
   62 
   63         /* Initialize state with identity permutation */
   64         for (i = 0; i < 256; i++)
   65                 state->perm[i] = (u_char)i; 
   66         state->index1 = 0;
   67         state->index2 = 0;
   68   
   69         /* Randomize the permutation using key data */
   70         for (j = i = 0; i < 256; i++) {
   71                 j += state->perm[i] + key[i % keylen]; 
   72                 swap_bytes(&state->perm[i], &state->perm[j]);
   73         }
   74 }
   75 
   76 /*
   77  * Encrypt some data using the supplied RC4 state buffer.
   78  * The input and output buffers may be the same buffer.
   79  * Since RC4 is a stream cypher, this function is used
   80  * for both encryption and decryption.
   81  */
   82 void
   83 rc4_crypt(struct rc4_state *const state,
   84         const u_char *inbuf, u_char *outbuf, int buflen)
   85 {
   86         int i;
   87         u_char j;
   88 
   89         for (i = 0; i < buflen; i++) {
   90 
   91                 /* Update modification indicies */
   92                 state->index1++;
   93                 state->index2 += state->perm[state->index1];
   94 
   95                 /* Modify permutation */
   96                 swap_bytes(&state->perm[state->index1],
   97                     &state->perm[state->index2]);
   98 
   99                 /* Encrypt/decrypt next byte */
  100                 j = state->perm[state->index1] + state->perm[state->index2];
  101                 outbuf[i] = inbuf[i] ^ state->perm[j];
  102         }
  103 }
  104 

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