--- /dev/null
+/* -*-c-*-
+ *
+ * The alleged RC4 stream cipher
+ *
+ * (c) 1999 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------*
+ *
+ * This file is part of Catacomb.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * Catacomb is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with Catacomb; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Notes on RC4 ------------------------------------------------------*
+ *
+ * RC4 is a stream cipher desgigned by Ron Rivest. For a while RC4 was a
+ * trade secret of RSA Data Security, Inc., but somehow source code for a
+ * cipher which interworks with RC4 was posted to the Cypherpunks mailing
+ * list.
+ */
+
+#ifndef CATACOMB_RC4_H
+#define CATACOMB_RC4_H
+
+#ifdef __cplusplus
+ extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <assert.h>
+
+#include <mLib/bits.h>
+
+#ifndef CATACOMB_GCIPHER_H
+# include "gcipher.h"
+#endif
+
+#ifndef CATACOMB_GRAND_H
+# include "grand.h"
+#endif
+
+/*----- Data structures ---------------------------------------------------*/
+
+typedef struct rc4_ctx {
+ unsigned i, j; /* Indices into the @S@ table */
+ unsigned f; /* Flags word */
+ octet s[256]; /* The ever-changing @S@ table */
+} rc4_ctx;
+
+#define RC4F_OPEN 1u
+
+/*----- Macros ------------------------------------------------------------*/
+
+/* --- @RC4_OPEN@ --- *
+ *
+ * Arguments: @ctx@ = pointer to an RC4 context
+ * @guts@ = code to perform within the RC4 context
+ *
+ * Use: Performs some code within an RC4 context. Some of the
+ * parameters are extracted from the context and held in local
+ * variables for speed. Multiple calls to @RC4_BYTE@ may be
+ * made within the open context. A context must only be
+ * opened once at a time.
+ */
+
+#define RC4_OPEN(ctx, guts) do { \
+ unsigned _rc4_i = (ctx)->i; \
+ unsigned _rc4_j = (ctx)->j; \
+ octet *_rc4_s = (ctx)->s; \
+ \
+ assert(((void)"RC4 context may only be opened once at a time", \
+ ((ctx)->f & RC4F_OPEN) == 0)); \
+ (ctx)->f |= RC4F_OPEN; \
+ \
+ guts \
+ \
+ (ctx)->f &= ~RC4F_OPEN; \
+ (ctx)->i = _rc4_i; \
+ (ctx)->j = _rc4_j; \
+} while (0)
+
+/* --- @RC4_BYTE@ --- *
+ *
+ * Arguments: @x@ = output variable to set
+ *
+ * Use: Extracts an octet from the lexically innermost open RC4
+ * context and places it in the variable @x@.
+ */
+
+#define RC4_BYTE(x) do { \
+ unsigned _si, _sj; \
+ _rc4_i = (_rc4_i + 1) & 0xff; \
+ _si = _rc4_s[_rc4_i]; \
+ _rc4_j = (_rc4_j + _si) & 0xff; \
+ _sj = _rc4_s[_rc4_j]; \
+ _rc4_s[_rc4_i] = _sj; \
+ _rc4_s[_rc4_j] = _si; \
+ (x) = _rc4_s[(_si + _sj) & 0xff]; \
+} while (0)
+
+/*----- Functions provided ------------------------------------------------*/
+
+/* --- @rc4_addkey@ --- *
+ *
+ * Arguments: @rc4_ctx *ctx@ = pointer to context to key
+ * @const void *k@ = pointer to key data to use
+ * @size_t sz@ = size of the key data
+ *
+ * Returns: ---
+ *
+ * Use: Mixes key data with an RC4 context. The RC4 context is not
+ * reset before mixing. This may be used to mix new key
+ * material with an existing RC4 context.
+ */
+
+extern void rc4_addkey(rc4_ctx */*ctx*/, const void */*k*/, size_t /*sz*/);
+
+/* --- @rc4_init@ --- *
+ *
+ * Arguments: @rc4_ctx *ctx@ = pointer to context to initialize
+ * @const void *k@ = pointer to key data to use
+ * @size_t sz@ = size of the key data
+ *
+ * Returns: ---
+ *
+ * Use: Initializes an RC4 context ready for use.
+ */
+
+extern void rc4_init(rc4_ctx */*ctx*/, const void */*k*/, size_t /*sz*/);
+
+/* --- @rc4_encrypt@ --- *
+ *
+ * Arguments: @rc4_ctx *ctx@ = pointer to context to use
+ * @const void *src@ = pointer to the source block
+ * @void *dest@ = pointer to the destination block
+ * @size_t sz@ = size of the block
+ *
+ * Returns: ---
+ *
+ * Use: Encrypts or decrypts a block of data. The destination may
+ * be null to just grind the generator around for a while. It's
+ * recommended that you say `@rc4_encrypt(&ctx, 0, 0, 1024)@'
+ * after initializing a new context, to prevent keystream
+ * guessing attacks. The source may be null to just extract a
+ * big lump of data from the generator.
+ */
+
+extern void rc4_encrypt(rc4_ctx */*ctx*/,
+ const void */*src*/, void */*dest*/,
+ size_t /*sz*/);
+
+/*----- Generic cipher interface ------------------------------------------*/
+
+#define RC4_KEYSZ 16
+extern const octet rc4_keysz[];
+
+extern const gccipher rc4;
+
+/*----- Generic random number generator interface -------------------------*/
+
+/* --- @rc4_rand@ --- *
+ *
+ * Arguments: @const void *k@ = pointer to key material
+ * @size_t sz@ = size of key material
+ *
+ * Returns: Pointer to generic random number generator interface.
+ *
+ * Use: Creates a random number interface wrapper around an
+ * OFB-mode block cipher.
+ */
+
+extern grand *rc4_rand(const void */*k*/, size_t /*sz*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+ }
+#endif
+
+#endif
projects / u / mdw / catacomb / blobdiff