X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/ba6e6b64033b1f9de49feccb5c9cd438354481f7..0f00dc4c8eb47e67bc0f148c2dd109f73a451e0a:/symm/ofb.h?ds=sidebyside

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+/* -*-c-*-
+ *
+ * Output feedback for block ciphers
+ *
+ * (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.
+ */
+
+#ifndef CATACOMB_OFB_H
+#define CATACOMB_OFB_H
+
+#ifdef __cplusplus
+  extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <stddef.h>
+
+#include <mLib/bits.h>
+
+#ifndef CATACOMB_GCIPHER_H
+#  include "gcipher.h"
+#endif
+
+#ifndef CATACOMB_GRAND_H
+#  include "grand.h"
+#endif
+
+/*----- Macros ------------------------------------------------------------*/
+
+/* --- @OFB_DECL@ --- *
+ *
+ * Arguments:	@PRE@, @pre@ = prefixes for block cipher definitions
+ *
+ * Use:		Makes declarations for output feedback mode.
+ */
+
+#define OFB_DECL(PRE, pre)						\
+									\
+/* --- Output feedback context --- */					\
+									\
+typedef struct pre##_ofbctx {						\
+  pre##_ctx ctx;			/* Underlying cipher context */	\
+  unsigned off;				/* Current offset in buffer */	\
+  octet iv[PRE##_BLKSZ];		/* Output buffer and IV */	\
+} pre##_ofbctx;								\
+									\
+/* --- @pre_ofbgetiv@ --- *						\
+ *									\
+ * Arguments:	@const pre_ofbctx *ctx@ = pointer to OFB context block	\
+ *		@void *iv@ = pointer to output data block		\
+ *									\
+ * Returns:	---							\
+ *									\
+ * Use:		Reads the currently set IV.  Reading and setting an IV	\
+ *		is not transparent to the cipher.  It will add a `step'	\
+ *		which must be matched by a similar operation during	\
+ *		decryption.						\
+ */									\
+									\
+extern void pre##_ofbgetiv(const pre##_ofbctx */*ctx*/,			\
+			   void */*iv*/);				\
+									\
+/* --- @pre_ofbsetiv@ --- *						\
+ *									\
+ * Arguments:	@pre_ofbctx *ctx@ = pointer to OFB context block	\
+ *		@cnost void *iv@ = pointer to IV to set			\
+ *									\
+ * Returns:	---							\
+ *									\
+ * Use:		Sets the IV to use for subsequent encryption.		\
+ */									\
+									\
+extern void pre##_ofbsetiv(pre##_ofbctx */*ctx*/,			\
+			   const void */*iv*/);				\
+									\
+/* --- @pre_ofbbdry@ --- *						\
+ *									\
+ * Arguments:	@pre_ofbctx *ctx@ = pointer to OFB context block	\
+ *									\
+ * Returns:	---							\
+ *									\
+ * Use:		Inserts a boundary during encryption.  Successful	\
+ *		decryption must place a similar boundary.		\
+ */									\
+									\
+extern void pre##_ofbbdry(pre##_ofbctx */*ctx*/);			\
+									\
+/* --- @pre_ofbsetkey@ --- *						\
+ *									\
+ * Arguments:	@pre_ofbctx *ctx@ = pointer to OFB context block	\
+ *		@const pre_ctx *k@ = pointer to cipher context		\
+ *									\
+ * Returns:	---							\
+ *									\
+ * Use:		Sets the OFB context to use a different cipher key.	\
+ */									\
+									\
+extern void pre##_ofbsetkey(pre##_ofbctx */*ctx*/,			\
+			    const pre##_ctx */*k*/);			\
+									\
+/* --- @pre_ofbinit@ --- *						\
+ *									\
+ * Arguments:	@pre_ofbctx *ctx@ = pointer to cipher context		\
+ *		@const void *key@ = pointer to the key buffer		\
+ *		@size_t sz@ = size of the key				\
+ *		@const void *iv@ = pointer to initialization vector	\
+ *									\
+ * Returns:	---							\
+ *									\
+ * Use:		Initializes a OFB context ready for use.  You should	\
+ *		ensure that the IV chosen is unique: reusing an IV will	\
+ *		compromise the security of the entire plaintext.  This	\
+ *		is equivalent to calls to @pre_init@, @pre_ofbsetkey@	\
+ *		and @pre_ofbsetiv@.					\
+ */									\
+									\
+extern void pre##_ofbinit(pre##_ofbctx */*ctx*/,			\
+			  const void */*key*/, size_t /*sz*/,		\
+			  const void */*iv*/);				\
+									\
+/* --- @pre_ofbencrypt@ --- *						\
+ *									\
+ * Arguments:	@pre_ofbctx *ctx@ = pointer to OFB context block	\
+ *		@const void *src@ = pointer to source data		\
+ *		@void *dest@ = pointer to destination data		\
+ *		@size_t sz@ = size of block to be encrypted		\
+ *									\
+ * Returns:	---							\
+ *									\
+ * Use:		Encrypts or decrypts a block with a block cipher in OFB	\
+ *		mode: encryption and decryption are the same in OFB.	\
+ *		The destination may be null to just churn the feedback	\
+ *		round for a bit.  The source may be null to use the	\
+ *		cipher as a random data generator.			\
+ */									\
+									\
+extern void pre##_ofbencrypt(pre##_ofbctx */*ctx*/,			\
+			     const void */*src*/, void */*dest*/,	\
+			     size_t /*sz*/);				\
+									\
+/* --- @pre_ofbrand@ --- *						\
+ *									\
+ * 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 *pre##_ofbrand(const void */*k*/, size_t /*sz*/);		\
+									\
+/* --- Generic cipher interface --- */					\
+									\
+extern const gccipher pre##_ofb;
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+  }
+#endif
+
+#endif