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+/* -*-c-*-
+ *
+ * The SEAL pseudo-random function family
+ *
+ * (c) 2000 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 the SEAL pseudo-random function family -------------------*
+ *
+ * SEAL is a slightly odd cryptographic primitive.  It was designed by Phil
+ * Rogaway and Don Coppersmith at IBM, basically as an exercise in producing
+ * a really fast symmetric cipher of some kind.  They succeeded: SEAL is
+ * faster than the much simpler RC4.
+ *
+ * For each key, it gives you %$2^{32}$% different output streams.  This
+ * implementation imposes no length limits on the size of output streams and
+ * performs careful buffer handling to allow arbitrary amounts of data to be
+ * extracted.  In practice, extracting more than about 64K is possibly dodgy
+ * from a security point of view.
+ *
+ * SEAL is patented.
+ */
+
+#ifndef CATACOMB_SEAL_H
+#define CATACOMB_SEAL_H
+
+#ifdef __cplusplus
+  extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#ifndef CATACOMB_GCIPHER_H
+#  include "gcipher.h"
+#endif
+
+#ifndef CATACOMB_GRAND_H
+#  include "grand.h"
+#endif
+
+/*----- Data structures ---------------------------------------------------*/
+
+#define SEAL_R 256
+
+typedef struct seal_key {
+  octet k[20];				/* Copy of the 160-bit key */
+  uint32 t[512];			/* Substitution table */
+  uint32 s[256];			/* Magic for each iteration */
+  uint32 r[SEAL_R];			/* Magic for the first 64K */
+} seal_key;
+
+typedef struct seal_ctx {
+  seal_key *k;				/* Pointer to the key block */
+  uint32 *r, ri;			/* Pointer to current magic */
+  uint32 n, l;				/* Various indices into things */
+  uint32 a, b, c, d;			/* Current chaining variables */
+  uint32 n1, n2, n3, n4;		/* Increments for the variables */
+  unsigned i;				/* Index into current iteration */
+  octet q[16];				/* Output buffer */
+  unsigned qsz;				/* Number of bytes in the buffer */
+  uint32 rbuf[SEAL_R];			/* Buffer for later magic */
+} seal_ctx;
+
+/*----- Functions provided ------------------------------------------------*/
+
+/* --- @seal_initkey@ --- *
+ *
+ * Arguments:	@seal_key *k@ = pointer to key block
+ *		@const void *buf@ = pointer to key material
+ *		@size_t sz@ = size of the key material
+ *
+ * Returns:	---
+ *
+ * Use:		Initializes a SEAL key block.  The key material may be any
+ *		size, but if it's not 20 bytes long it's passed to SHA for
+ *		hashing first.
+ */
+
+extern void seal_initkey(seal_key */*k*/,
+			 const void */*buf*/, size_t /*sz*/);
+
+/* --- @seal_initctx@ --- *
+ *
+ * Arguments:	@seal_ctx *c@ = pointer to a SEAL context
+ *		@seal_key *k@ = pointer to a SEAL key
+ *		@uint32 n@ = integer sequence number
+ *
+ * Returns:	---
+ *
+ * Use:		Initializes a SEAL context which can be used for random
+ *		number generation or whatever.
+ */
+
+extern void seal_initctx(seal_ctx */*c*/, seal_key */*k*/, uint32 /*n*/);
+
+/* --- @seal_encrypt@ --- *
+ *
+ * Arguments:	@seal_ctx *c@ = pointer to a SEAL context
+ *		@const void *src@ = pointer to source data
+ *		@void *dest@ = pointer to destination data
+ *		@size_t sz@ = size of the data
+ *
+ * Returns:	---
+ *
+ * Use:		Encrypts a block of data using SEAL.  If @src@ is zero,
+ *		@dest@ is filled with SEAL output.  If @dest@ is zero, the
+ *		SEAL generator is just spun around for a bit.  This shouldn't
+ *		be necessary, because SEAL isn't RC4.
+ */
+
+extern void seal_encrypt(seal_ctx */*c*/, const void */*src*/,
+			 void */*dest*/, size_t /*sz*/);
+
+/*----- Generic cipher interface ------------------------------------------*/
+
+#define SEAL_KEYSZ 20
+extern const octet seal_keysz[];
+
+extern const gccipher seal;
+
+/*----- Generic random number generator interface -------------------------*/
+
+/* --- @seal_rand@ --- *
+ *
+ * Arguments:	@const void *k@ = pointer to key material
+ *		@size_t sz@ = size of key material
+ *		@uint32 n@ = sequence number
+ *
+ * Returns:	Pointer to generic random number generator interface.
+ *
+ * Use:		Creates a random number interface wrapper around a SEAL
+ *		pseudorandom function.
+ */
+
+extern grand *seal_rand(const void */*k*/, size_t /*sz*/, uint32 /*n*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+  }
+#endif
+
+#endif