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Diffstat (limited to 'rc4.c')
| -rw-r--r-- | rc4.c | 105 |
1 files changed, 105 insertions, 0 deletions
@@ -0,0 +1,105 @@ +/*! \file rc4.c + \brief Source file for RC4 stream cipher routines + \author Damien Miller <djm@mindrot.org> + \version 0.0.0 + \date 1999 + + A simple implementation of the RC4 stream cipher, based on the + description given in _Bruce Schneier's_ "Applied Cryptography" + 2nd edition. + + Copyright 1999 Damien Miller + + Permission is hereby granted, free of charge, to any person + obtaining a copy of this software and associated documentation + files (the "Software"), to deal in the Software without + restriction, including without limitation the rights to use, copy, + modify, merge, publish, distribute, sublicense, and/or sell copies + of the Software, and to permit persons to whom the Software is + furnished to do so, subject to the following conditions: + + The above copyright notice and this permission notice shall be + included in all copies or substantial portions of the Software. + + THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY + KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE + WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE + AND NONINFRINGEMENT. IN NO EVENT SHALL DAMIEN MILLER BE LIABLE + FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF + CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION + WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. + + \warning None of these functions clears its memory after use. It + \warning is the responsability of the calling routines to ensure + \warning that any sensitive data (keystream, key or plaintext) is + \warning properly erased after use. + + \warning The name "RC4" is trademarked in the United States, + \warning you may need to use "RC4 compatible" or "ARC4" + \warning (Alleged RC4). +*/ + +/* $Id: rc4.c,v 1.1.1.1 1999/10/26 05:48:13 damien Exp $ */ + +#include "rc4.h" + + +void rc4_key(rc4_t *r, unsigned char *key, int len) +{ + int t; + + for(r->i = 0; r->i < 256; r->i++) + r->s[r->i] = r->i; + + r->j = 0; + for(r->i = 0; r->i < 256; r->i++) + { + r->j = (r->j + r->s[r->i] + key[r->i % len]) % 256; + t = r->s[r->i]; + r->s[r->i] = r->s[r->j]; + r->s[r->j] = t; + } + r->i = r->j = 0; +} + +void rc4_crypt(rc4_t *r, unsigned char *plaintext, int len) +{ + int t; + int c; + + c = 0; + while(c < len) + { + r->i = (r->i + 1) % 256; + r->j = (r->j + r->s[r->i]) % 256; + t = r->s[r->i]; + r->s[r->i] = r->s[r->j]; + r->s[r->j] = t; + + t = (r->s[r->i] + r->s[r->j]) % 256; + + plaintext[c] ^= r->s[t]; + c++; + } +} + +void rc4_getbytes(rc4_t *r, unsigned char *buffer, int len) +{ + int t; + int c; + + c = 0; + while(c < len) + { + r->i = (r->i + 1) % 256; + r->j = (r->j + r->s[r->i]) % 256; + t = r->s[r->i]; + r->s[r->i] = r->s[r->j]; + r->s[r->j] = t; + + t = (r->s[r->i] + r->s[r->j]) % 256; + + buffer[c] = r->s[t]; + c++; + } +} |