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   1 /* -*-c-*-
   2  *
   3  * $Id: dsa.h,v 1.2 1999/11/20 22:23:48 mdw Exp $
   4  *
   5  * Digital Signature Algorithm
   6  *
   7  * (c) 1999 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: dsa.h,v $
  33  * Revision 1.2  1999/11/20 22:23:48  mdw
  34  * Allow event handler to abort the search process.
  35  *
  36  * Revision 1.1  1999/11/19 19:28:00  mdw
  37  * Implementation of the Digital Signature Algorithm.
  38  *
  39  */
  40
  41 #ifndef DSA_H
  42 #define DSA_H
  43
  44 #ifdef __cplusplus
  45   extern "C" {
  46 #endif
  47
  48 /*----- Notes on the Digital Signature Algorithm --------------------------*
  49  *
  50  * The Digital Signature Algorithm was designed by the NSA for US Government
  51  * use.  It's defined in FIPS 186-1.  Whether it's covered by patents is
  52  * under dispute, although it looks relatively clear.  It produces compact
  53  * signatures, and is relatively easy to compute.  It seems strong, if
  54  * appropriate parameters are chosen.
  55  */
  56
  57 /*----- Header files ------------------------------------------------------*/
  58
  59 #ifndef MP_H
  60 #  include "mp.h"
  61 #endif
  62
  63 /*----- Event codes -------------------------------------------------------*/
  64
  65 enum {
  66   DSAEV_OK,                             /* Everything is fine */
  67
  68   DSAEV_FAILQ,                          /* @q@ failed primality test */
  69   DSAEV_PASSQ,                          /* @q@ passeed one iteration */
  70   DSAEV_GOODQ,                          /* Found good prime @q@ */
  71
  72   DSAEV_TRYP,                           /* Try prospective @p@ */
  73   DSAEV_FAILP,                          /* @p@ failed primality test */
  74   DSAEV_PASSP,                          /* @p@ passed one iteration */
  75   DSAEV_GOODP,                          /* @p@ accepted as being prime */
  76
  77   DSAEV_TRYH,                           /* Try prospective @h@ */
  78   DSAEV_FAILH,                          /* @h@ failed */
  79   DSAEV_GOODG                           /* @g@ accepted as a generator */
  80 };
  81
  82 /*----- Data structures ---------------------------------------------------*/
  83
  84 /* --- DSA parameter structure --- *
  85  *
  86  * These parameters can, and probably should, be shared among a group of
  87  * users.
  88  */
  89
  90 typedef struct dsa_param {
  91   mp *p, *q;                            /* Prime numbers %$p$% and %$q$% */
  92   mp *g;                                /* Generates order-%$q$% subgroup */
  93 } dsa_param;
  94
  95 /* --- DSA signature structure --- *
  96  *
  97  * This is the recommended structure for a DSA signature.  The actual signing
  98  * function can cope with arbitrary-sized objects given appropriate
  99  * parameters, however.
 100  */
 101
 102 #define DSA_SIGLEN 20
 103
 104 typedef struct dsa_sig {
 105   octet r[DSA_SIGLEN];                  /* 160-bit @r@ value */
 106   octet s[DSA_SIGLEN];                  /* 160-bit @s@ value */
 107 } dsa_sig;
 108
 109 /*----- Functions provided ------------------------------------------------*/
 110
 111 /* --- @dsa_seed@ --- *
 112  *
 113  * Arguments:   @dsa_param *dp@ = where to store parameters
 114  *              @unsigned l@ = bitlength of @p@ in bits
 115  *              @const void *k@ = pointer to key material
 116  *              @int (*proc)(int ev, mp *m, void *p)@ = event procedure
 117  *              @size_t sz@ = size of key material
 118  *
 119  * Returns:     Zero if all went well, nonzero if key material was
 120  *              unsuitable (one of the @DSAEV@ codes).
 121  *
 122  * Use:         Generates the DSA shared parameters from a given seed value.
 123  *              This can take quite a long time.  The size of @p@ in bits is
 124  *              %$l = 512 + 64l'$%.  The DSA standard, FIPS 186, only allows
 125  *              %$0 \le l' \le 8$%.  This implementation has no such limit,
 126  *              although @l@ must be a multiple of 8.
 127  *
 128  *              The event procedure is informed of various happenings during
 129  *              generation.  It is passed an event code describing what
 130  *              happened, and a multiprecision number which pertains to the
 131  *              event code.  It may abort the search at any time by returning
 132  *              a nonzero value, which is returned as the result of the
 133  *              function.
 134  */
 135
 136 extern int dsa_seed(dsa_param */*dp*/, unsigned /*l*/,
 137                     const void */*k*/, size_t /*sz*/,
 138                     int (*proc)(int /*ev*/, mp */*m*/, void */*p*/),
 139                     void */*p*/);
 140
 141 /* --- @dsa_mksig@ --- *
 142  *
 143  * Arguments:   @const dsa_param *dp@ = pointer to DSA parameters
 144  *              @const mp *a@ = secret signing key
 145  *              @const mp *m@ = message to be signed
 146  *              @const mp *k@ = random data
 147  *              @mp **rr, **ss@ = where to put output parameters
 148  *
 149  * Returns:     ---
 150  *
 151  * Use:         Computes a DSA signature of a message.
 152  */
 153
 154 extern void dsa_mksig(const dsa_param */*dp*/, const mp */*a*/,
 155                       const mp */*m*/, const mp */*k*/,
 156                       mp **/*rr*/, mp **/*ss*/);
 157
 158 /* --- @dsa_sign@ --- *
 159  *
 160  * Arguments:   @dsa_param *dp@ = pointer to DSA parameters
 161  *              @mp *a@ = pointer to secret signing key
 162  *              @const void *m@ = pointer to message
 163  *              @size_t msz@ = size of the message
 164  *              @const void *k@ = secret random data for securing signature
 165  *              @size_t ksz@ = size of secret data
 166  *              @void *r@ = pointer to output space for @r@
 167  *              @size_t rsz@ = size of output space for @r@
 168  *              @void *s@ = pointer to output space for @s@
 169  *              @size_t ssz@ = size of output space for @s@
 170  *
 171  * Returns:     ---
 172  *
 173  * Use:         Signs a message, storing the results in a big-endian binary
 174  *              form.
 175  */
 176
 177 extern void dsa_sign(dsa_param */*dp*/, mp */*a*/,
 178                      const void */*m*/, size_t /*msz*/,
 179                      const void */*k*/, size_t /*ksz*/,
 180                      void */*r*/, size_t /*rsz*/,
 181                      void */*s*/, size_t /*ssz*/);
 182
 183 /* --- @dsa_vrfy@ --- *
 184  *
 185  * Arguments:   @const dsa_param *dp@ = pointer to DSA parameters
 186  *              @const mp *y@ = public verification key
 187  *              @const mp *m@ = message which was signed
 188  *              @const mp *r, *s@ = the signature
 189  *
 190  * Returns:     Zero if the signature is a forgery, nonzero if it's valid.
 191  *
 192  * Use:         Verifies a DSA digital signature.
 193  */
 194
 195 extern int dsa_vrfy(const dsa_param */*dp*/, const mp */*y*/,
 196                     const mp */*m*/, const mp */*r*/, const mp */*s*/);
 197
 198 /* --- @dsa_verify@ --- *
 199  *
 200  * Arguments:   @const dsa_param *dp@ = pointer to DSA parameters
 201  *              @const mp *y@ = public verification key
 202  *              @const void *m@ = pointer to message block
 203  *              @size_t msz@ = size of message block
 204  *              @const void *r@ = pointer to @r@ signature half
 205  *              @size_t rsz@ = size of @r@
 206  *              @const void *s@ = pointer to @s@ signature half
 207  *              @size_t ssz@ = size of @s@
 208  *
 209  * Returns:     Zero if the signature is a forgery, nonzero if it's valid.
 210  *
 211  * Use:         Verifies a DSA digital signature.
 212  */
 213
 214 extern int dsa_verify(const dsa_param */*dp*/, const mp */*y*/,
 215                const void */*m*/, size_t /*msz*/,
 216                const void */*r*/, size_t /*rsz*/,
 217                const void */*s*/, size_t /*ssz*/);
 218
 219 /*----- That's all, folks -------------------------------------------------*/
 220
 221 #ifdef __cplusplus
 222   }
 223 #endif
 224
 225 #endif