106 lines
2.7 KiB
C
106 lines
2.7 KiB
C
/*! \file rc4.c
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\brief Source file for RC4 stream cipher routines
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\author Damien Miller <djm@mindrot.org>
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\version 0.0.0
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\date 1999
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A simple implementation of the RC4 stream cipher, based on the
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description given in _Bruce Schneier's_ "Applied Cryptography"
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2nd edition.
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Copyright 1999 Damien Miller
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Permission is hereby granted, free of charge, to any person
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obtaining a copy of this software and associated documentation
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files (the "Software"), to deal in the Software without
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restriction, including without limitation the rights to use, copy,
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modify, merge, publish, distribute, sublicense, and/or sell copies
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of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
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KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
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WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
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AND NONINFRINGEMENT. IN NO EVENT SHALL DAMIEN MILLER BE LIABLE
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FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
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CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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\warning None of these functions clears its memory after use. It
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\warning is the responsability of the calling routines to ensure
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\warning that any sensitive data (keystream, key or plaintext) is
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\warning properly erased after use.
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\warning The name "RC4" is trademarked in the United States,
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\warning you may need to use "RC4 compatible" or "ARC4"
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\warning (Alleged RC4).
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*/
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/* $Id: rc4.c,v 1.1.1.1 1999/10/26 05:48:13 damien Exp $ */
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#include "rc4.h"
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void rc4_key(rc4_t *r, unsigned char *key, int len)
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{
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int t;
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for(r->i = 0; r->i < 256; r->i++)
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r->s[r->i] = r->i;
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r->j = 0;
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for(r->i = 0; r->i < 256; r->i++)
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{
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r->j = (r->j + r->s[r->i] + key[r->i % len]) % 256;
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t = r->s[r->i];
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r->s[r->i] = r->s[r->j];
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r->s[r->j] = t;
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}
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r->i = r->j = 0;
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}
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void rc4_crypt(rc4_t *r, unsigned char *plaintext, int len)
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{
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int t;
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int c;
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c = 0;
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while(c < len)
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{
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r->i = (r->i + 1) % 256;
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r->j = (r->j + r->s[r->i]) % 256;
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t = r->s[r->i];
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r->s[r->i] = r->s[r->j];
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r->s[r->j] = t;
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t = (r->s[r->i] + r->s[r->j]) % 256;
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plaintext[c] ^= r->s[t];
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c++;
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}
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}
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void rc4_getbytes(rc4_t *r, unsigned char *buffer, int len)
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{
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int t;
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int c;
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c = 0;
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while(c < len)
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{
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r->i = (r->i + 1) % 256;
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r->j = (r->j + r->s[r->i]) % 256;
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t = r->s[r->i];
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r->s[r->i] = r->s[r->j];
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r->s[r->j] = t;
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t = (r->s[r->i] + r->s[r->j]) % 256;
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buffer[c] = r->s[t];
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c++;
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}
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}
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