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+/*! \file rc4.h
+    \brief Header 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.h,v 1.1.1.1 1999/10/26 05:48:13 damien Exp $ */
+
+#ifndef _RC4_H
+#define _RC4_H
+
+/*! \struct rc4_t
+    \brief RC4 stream cipher state object
+         \var s State array
+         \var i Monotonic index
+         \var j Randomised index
+         
+         \warning This structure should not be accessed directly. To
+         \warning initialise a rc4_t object, you should use the rc4_key()
+         \warning function
+         
+         This structure holds the current state of the RC4 algorithm.
+*/
+typedef struct
+{
+        unsigned int s[256];
+        int i;
+        int j;
+} rc4_t;
+
+/*! \fn void rc4_key(rc4_t *r, unsigned char *key, int len);
+    \brief Set up key structure of RC4 stream cipher
+         \param r pointer to RC4 structure to be seeded
+         \param key pointer to buffer containing raw key
+         \param len length of key
+         
+         This function set the internal state of the RC4 data structure
+         pointed to by \a r using the specified \a key of length \a len.
+         
+         This function can use up to 256 bytes of key, any more are ignored.
+         
+         \warning Stream ciphers (such as RC4) can be insecure if the same
+         \warning key is used repeatedly. Ensure that any key specified has
+         \warning an reasonably sized Initialisation Vector component.
+*/
+void rc4_key(rc4_t *r, unsigned char *key, int len);
+
+/*! \fn rc4_crypt(rc4_t *r, unsigned char *plaintext, int len);
+    \brief Crypt bytes using RC4 algorithm
+         \param r pointer to RC4 structure to be used
+         \param plaintext Pointer to bytes to encrypt
+         \param len number of bytes to crypt
+
+         This function encrypts one or more bytes (pointed to by \a plaintext)
+         using the RC4 algorithm. \a r is a state structure that must be 
+         initialiased using the rc4_key() function prior to use.
+         
+         Since RC4 XORs each byte of plaintext with a byte of keystream,
+         this function can be used for both encryption and decryption.
+*/
+void rc4_crypt(rc4_t *r, unsigned char *plaintext, int len);
+
+/*! \fn rc4_getbytes(rc4_t *r, unsigned char *buffer, int len);
+    \brief Generate key stream using the RC4 stream cipher
+         \param r pointer to RC4 structure to be used
+         \param buffer pointer to buffer in which to deposit keystream
+         \param len number of bytes to deposit
+
+         This function gives access to the raw RC4 key stream. In this 
+         consiguration RC4 can be used as a fast, strong pseudo-random 
+         number generator with a very long period.
+*/
+void rc4_getbytes(rc4_t *r, unsigned char *buffer, int len);
+
+#endif /* _RC4_H */