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[u/mdw/catacomb] / pub / gdsa.h

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+/* -*-c-*-
+ *
+ * Generalized version of DSA
+ *
+ * (c) 2004 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_GDSA_H
+#define CATACOMB_GDSA_H
+
+#ifdef __cplusplus
+  extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#ifndef CATACOMB_GHASH_H
+#  include "ghash.h"
+#endif
+
+#ifndef CATACOMB_GROUP_H
+#  include "group.h"
+#endif
+
+/*----- Data structures ---------------------------------------------------*/
+
+/* --- GDSA context --- *
+ *
+ * You don't need to fill in all of this stuff.  See the description of the
+ * function you want to use to find out what members are needed.
+ */
+
+typedef struct gdsa {
+  group *g;                            /* The group we work in */
+  mp *u;                               /* Private key, for signing */
+  ge *p;                               /* Public key, for verifying */
+  grand *r;                            /* Random number source */
+  const gchash *h;                     /* Hash function */
+} gdsa;
+
+/* --- GDSA signatures --- */
+
+typedef struct gdsa_sig { mp *r, *s; } gdsa_sig;
+#define GDSA_SIG_INIT { MP_NEW, MP_NEW }
+
+/*----- Functions provided ------------------------------------------------*/
+
+/* --- @gdsa_beginhash@ --- *
+ *
+ * Arguments:  @const gdsa *c@ = pointer to the context structure
+ *
+ * Returns:    A hashing context for you to hash the message.
+ *
+ * Use:                Initializes a hash function correctly for you to hash a
+ *             message.  Requires @h@.
+ */
+
+extern ghash *gdsa_beginhash(const gdsa */*c*/);
+
+/* --- @gdsa_endhash@ --- *
+ *
+ * Arguments:  @const gdsa *c@ = pointer to the context structure
+ *             @ghash *h@ = the hashing context
+ *
+ * Returns:    ---
+ *
+ * Use:                Does any final thing that DSA wants to do when hashing a
+ *             message.  (Actually, there's nothing.)  The hashing context
+ *             isn't finalized.
+ */
+
+extern void gdsa_endhash(const gdsa */*c*/, ghash */*h*/);
+
+/* --- @gdsa_sign@ --- *
+ *
+ * Arguments:  @const gdsa *c@ = my context structure
+ *             @gdsa_sig *s@ = where to put the signature (initialized)
+ *             @const void *m@ = pointer to message hash
+ *             @mp *k@ = random exponent for this message or null
+ *
+ * Returns:    ---
+ *
+ * Use:                Signs a message.  Requires @g@, @u@, @h@, and @r@ if @k@ is
+ *             null.  This is a better idea than inventing @k@ yourself.
+ */
+
+extern void gdsa_sign(const gdsa */*c*/, gdsa_sig */*s*/,
+                     const void */*m*/, mp */*k*/);
+
+/* --- @gdsa_verify@ --- *
+ *
+ * Arguments:  @const gdsa *c@ = my context structure
+ *             @const gdsa_sig *s@ = the signature to verify
+ *             @const void *m@ = pointer to message hash
+ *
+ * Returns:    Zero if OK, negative on failure.
+ *
+ * Use:                Checks a signature on a message,  Requires @g@, @p@, @h@.
+ */
+
+extern int gdsa_verify(const gdsa */*c*/, const gdsa_sig */*s*/,
+                      const void */*m*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+  }
+#endif
+
+#endif