X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/ba6e6b64033b1f9de49feccb5c9cd438354481f7..0f00dc4c8eb47e67bc0f148c2dd109f73a451e0a:/rand/dsarand.h

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+/* -*-c-*-
+ *
+ * Random number generator for DSA
+ *
+ * (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_DSARAND_H
+#define CATACOMB_DSARAND_H
+
+#ifdef __cplusplus
+  extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <mLib/bits.h>
+
+#ifndef CATACOMB_GRAND_H
+#  include "grand.h"
+#endif
+
+#ifndef CATACOMB_SHA_H
+#  include "sha.h"
+#endif
+
+/*----- Data structures ---------------------------------------------------*/
+
+typedef struct dsarand {
+  octet *p;				/* Pointer to seed (modified) */
+  size_t sz;				/* Size of the seed buffer */
+  unsigned passes;			/* Number of passes to make */
+} dsarand;
+
+/*----- Functions provided ------------------------------------------------*/
+
+/* --- @dsarand_init@ --- *
+ *
+ * Arguments:	@dsarand *d@ = pointer to context
+ *		@const void *p@ = pointer to seed buffer
+ *		@size_t sz@ = size of the buffer
+ *
+ * Returns:	---
+ *
+ * Use:		Initializes a DSA random number generator.
+ */
+
+extern void dsarand_init(dsarand */*d*/, const void */*p*/, size_t /*sz*/);
+
+/* --- @dsarand_reseed@ --- *
+ *
+ * Arguments:	@dsarand *d@ = pointer to context
+ *		@const void *p@ = pointer to seed buffer
+ *		@size_t sz@ = size of the buffer
+ *
+ * Returns:	---
+ *
+ * Use:		Initializes a DSA random number generator.
+ */
+
+extern void dsarand_reseed(dsarand */*d*/, const void */*p*/, size_t /*sz*/);
+
+/* --- @dsarand_destroy@ --- *
+ *
+ * Arguments:	@dsarand *d@ = pointer to context
+ *
+ * Returns:	---
+ *
+ * Use:		Disposes of a DSA random number generation context.
+ */
+
+extern void dsarand_destroy(dsarand */*d*/);
+
+/* --- @dsarand_fill@ --- *
+ *
+ * Arguments:	@dsarand *d@ = pointer to context
+ *		@void *p@ = pointer to output buffer
+ *		@size_t sz@ = size of output buffer
+ *
+ * Returns:	---
+ *
+ * Use:		Fills an output buffer with pseudorandom data.
+ *
+ *		Let %$p$% be the numerical value of the input buffer, and let
+ *		%$b$% be the number of bytes required.  Let
+ *		%$z = \lceil b / 20 \rceil$% be the number of SHA outputs
+ *		required.  Then the output of pass %$n$% is
+ *
+ *		  %$P_n = \sum_{0 \le i < z} 2^{160i} SHA(p + nz + i)$%
+ *							%${} \bmod 2^{8b}$%
+ *
+ *		and the actual result in the output buffer is the XOR of all
+ *		of the output passes.
+ *
+ *		The DSA procedure for choosing @q@ involves two passes with
+ *		%$z = 1$%; the procedure for choosing @p@ involves one pass
+ *		with larger %$z$%.  This generalization of the DSA generation
+ *		procedure is my own invention but it seems relatively sound.
+ */
+
+extern void dsarand_fill(dsarand */*d*/, void */*p*/, size_t /*sz*/);
+
+/*----- Generic pseudorandom-number generator interface -------------------*/
+
+/* --- Miscellaneous operations --- */
+
+enum {
+  DSARAND_PASSES = GRAND_SPECIFIC('D'),	/* @unsigned n@ */
+  DSARAND_SEEDSZ,			/* No args */
+  DSARAND_GETSEED			/* @void *buf@ */
+};
+
+/* --- @dsarand_create@ --- *
+ *
+ * Arguments:	@const void *p@ = pointer to seed buffer
+ *		@size_t sz@ = size of seed buffer
+ *
+ * Returns:	Pointer to a generic generator.
+ *
+ * Use:		Constructs a generic generator interface to a DSA generator.
+ */
+
+extern grand *dsarand_create(const void */*p*/, size_t /*sz*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+  }
+#endif
+
+#endif