git.distorted.org.uk Git - u/mdw/catacomb/blob - dsa.h

   1 /* -*-c-*-
   2  *
   3  * $Id: dsa.h,v 1.4 1999/12/22 15:52:44 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 1.4  1999/12/22 15:52:44  mdw
  34  * Reworking for new prime-search system.
  35  *
  36  * Revision 1.3  1999/12/10 23:29:48  mdw
  37  * Change header file guard names.
  38  *
  39  * Revision 1.2  1999/11/20 22:23:48  mdw
  40  * Allow event handler to abort the search process.
  41  *
  42  * Revision 1.1  1999/11/19 19:28:00  mdw
  43  * Implementation of the Digital Signature Algorithm.
  44  *
  45  */
  46
  47 #ifndef CATACOMB_DSA_H
  48 #define CATACOMB_DSA_H
  49
  50 #ifdef __cplusplus
  51   extern "C" {
  52 #endif
  53
  54 /*----- Notes on the Digital Signature Algorithm --------------------------*
  55  *
  56  * The Digital Signature Algorithm was designed by the NSA for US Government
  57  * use.  It's defined in FIPS 186-1.  Whether it's covered by patents is
  58  * under dispute, although it looks relatively clear.  It produces compact
  59  * signatures, and is relatively easy to compute.  It seems strong, if
  60  * appropriate parameters are chosen.
  61  */
  62
  63 /*----- Header files ------------------------------------------------------*/
  64
  65 #ifndef CATACOMB_MP_H
  66 #  include "mp.h"
  67 #endif
  68
  69 #ifndef CATACOMB_PGEN_H
  70 #  include "pgen.h"
  71 #endif
  72
  73 /*----- Data structures ---------------------------------------------------*/
  74
  75 /* --- DSA parameter structure --- *
  76  *
  77  * These parameters can, and probably should, be shared among a group of
  78  * users.
  79  */
  80
  81 typedef struct dsa_param {
  82   mp *p, *q;                            /* Prime numbers %$p$% and %$q$% */
  83   mp *g;                                /* Generates order-%$q$% subgroup */
  84 } dsa_param;
  85
  86 /* --- DSA signature structure --- *
  87  *
  88  * This is the recommended structure for a DSA signature.  The actual signing
  89  * function can cope with arbitrary-sized objects given appropriate
  90  * parameters, however.
  91  */
  92
  93 #define DSA_SIGLEN 20
  94
  95 typedef struct dsa_sig {
  96   octet r[DSA_SIGLEN];                  /* 160-bit @r@ value */
  97   octet s[DSA_SIGLEN];                  /* 160-bit @s@ value */
  98 } dsa_sig;
  99
 100 /*----- DSA stepper -------------------------------------------------------*/
 101
 102 typedef struct dsa_stepctx {
 103
 104   /* --- To be initialized by the client --- */
 105
 106   grand *r;                             /* Random number generator */
 107   mp *q;                                /* Force @p@ to be a multiple */
 108   size_t bits;                          /* Number of bits in the result */
 109   unsigned or;                          /* OR mask for low order bits */
 110 } dsa_stepctx;
 111
 112 /* --- @dsa_step@ --- *
 113  *
 114  * The stepper chooses random integers, ensures that they are a multiple of
 115  * @q@ (if specified), sets the low-order bits, and then tests for
 116  * divisibility by small primes.
 117  */
 118
 119 extern int dsa_step(int /*rq*/, pgen_event */*ev*/, void */*p*/);
 120
 121 /*----- Functions provided ------------------------------------------------*/
 122
 123 /* --- @dsa_seed@ --- *
 124  *
 125  * Arguments:   @dsa_param *dp@ = where to store parameters
 126  *              @unsigned ql@ = length of @q@ in bits
 127  *              @unsigned pl@ = length of @p@ in bits
 128  *              @unsigned steps@ = number of steps to find @q@
 129  *              @const void *k@ = pointer to key material
 130  *              @size_t sz@ = size of key material
 131  *              @pgen_proc *event@ = event handler function
 132  *              @void *ectx@ = argument for event handler
 133  *
 134  * Returns:     @PGEN_DONE@ if everything worked ok; @PGEN_ABORT@ otherwise.
 135  *
 136  * Use:         Generates the DSA shared parameters from a given seed value.
 137  *              This can take quite a long time.
 138  *
 139  *              The algorithm used is a compatible extension of the method
 140  *              described in the DSA standard, FIPS 186.  The standard
 141  *              requires that %$q$% be 160 bits in size (i.e., @ql == 160@)
 142  *              and that the length of %$p$% be %$L = 512 + 64l$% for some
 143  *              %$l$%.  Neither limitation applies to this implementation.
 144  */
 145
 146 extern int dsa_seed(dsa_param */*dp*/, unsigned /*ql*/, unsigned /*pl*/,
 147                     unsigned /*steps*/, const void */*k*/, size_t /*sz*/,
 148                     pgen_proc */*event*/, void */*ectx*/);
 149
 150 /* --- @dsa_mksig@ --- *
 151  *
 152  * Arguments:   @const dsa_param *dp@ = pointer to DSA parameters
 153  *              @mp *a@ = secret signing key
 154  *              @mp *m@ = message to be signed
 155  *              @mp *k@ = random data
 156  *              @mp **rr, **ss@ = where to put output parameters
 157  *
 158  * Returns:     ---
 159  *
 160  * Use:         Computes a DSA signature of a message.
 161  */
 162
 163 extern void dsa_mksig(const dsa_param */*dp*/, mp */*a*/,
 164                       mp */*m*/, mp */*k*/,
 165                       mp **/*rr*/, mp **/*ss*/);
 166
 167 /* --- @dsa_sign@ --- *
 168  *
 169  * Arguments:   @dsa_param *dp@ = pointer to DSA parameters
 170  *              @mp *a@ = pointer to secret signing key
 171  *              @const void *m@ = pointer to message
 172  *              @size_t msz@ = size of the message
 173  *              @const void *k@ = secret random data for securing signature
 174  *              @size_t ksz@ = size of secret data
 175  *              @void *r@ = pointer to output space for @r@
 176  *              @size_t rsz@ = size of output space for @r@
 177  *              @void *s@ = pointer to output space for @s@
 178  *              @size_t ssz@ = size of output space for @s@
 179  *
 180  * Returns:     ---
 181  *
 182  * Use:         Signs a message, storing the results in a big-endian binary
 183  *              form.
 184  */
 185
 186 extern void dsa_sign(dsa_param */*dp*/, mp */*a*/,
 187                      const void */*m*/, size_t /*msz*/,
 188                      const void */*k*/, size_t /*ksz*/,
 189                      void */*r*/, size_t /*rsz*/,
 190                      void */*s*/, size_t /*ssz*/);
 191
 192 /* --- @dsa_vrfy@ --- *
 193  *
 194  * Arguments:   @const dsa_param *dp@ = pointer to DSA parameters
 195  *              @mp *y@ = public verification key
 196  *              @mp *m@ = message which was signed
 197  *              @mp *r, *s@ = the signature
 198  *
 199  * Returns:     Zero if the signature is a forgery, nonzero if it's valid.
 200  *
 201  * Use:         Verifies a DSA digital signature.
 202  */
 203
 204 extern int dsa_vrfy(const dsa_param */*dp*/, mp */*y*/,
 205                     mp */*m*/, mp */*r*/, mp */*s*/);
 206
 207 /* --- @dsa_verify@ --- *
 208  *
 209  * Arguments:   @const dsa_param *dp@ = pointer to DSA parameters
 210  *              @mp *y@ = public verification key
 211  *              @const void *m@ = pointer to message block
 212  *              @size_t msz@ = size of message block
 213  *              @const void *r@ = pointer to @r@ signature half
 214  *              @size_t rsz@ = size of @r@
 215  *              @const void *s@ = pointer to @s@ signature half
 216  *              @size_t ssz@ = size of @s@
 217  *
 218  * Returns:     Zero if the signature is a forgery, nonzero if it's valid.
 219  *
 220  * Use:         Verifies a DSA digital signature.
 221  */
 222
 223 extern int dsa_verify(const dsa_param */*dp*/, mp */*y*/,
 224                const void */*m*/, size_t /*msz*/,
 225                const void */*r*/, size_t /*rsz*/,
 226                const void */*s*/, size_t /*ssz*/);
 227
 228 /*----- That's all, folks -------------------------------------------------*/
 229
 230 #ifdef __cplusplus
 231   }
 232 #endif
 233
 234 #endif