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

   1 /* -*-c-*-
   2  *
   3  * Digital Signature Algorithm
   4  *
   5  * (c) 1999 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of Catacomb.
  11  *
  12  * Catacomb is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * Catacomb is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with Catacomb; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 #ifndef CATACOMB_DSA_H
  29 #define CATACOMB_DSA_H
  30
  31 #ifdef __cplusplus
  32   extern "C" {
  33 #endif
  34
  35 /*----- Notes on the Digital Signature Algorithm --------------------------*
  36  *
  37  * The Digital Signature Algorithm was designed by the NSA for US Government
  38  * use.  It's defined in FIPS 186-1.  Whether it's covered by patents is
  39  * under dispute, although it looks relatively clear.  It produces compact
  40  * signatures, and is relatively easy to compute.  It seems strong, if
  41  * appropriate parameters are chosen.
  42  */
  43
  44 /*----- Header files ------------------------------------------------------*/
  45
  46 #ifndef CATACOMB_DH_H
  47 #  include "dh.h"
  48 #endif
  49
  50 #ifndef CATACOMB_KEY_H
  51 #  include "key.h"
  52 #endif
  53
  54 #ifndef CATACOMB_KEYCHECK_H
  55 #  include "keycheck.h"
  56 #endif
  57
  58 #ifndef CATACOMB_MP_H
  59 #  include "mp.h"
  60 #endif
  61
  62 #ifndef CATACOMB_PGEN_H
  63 #  include "pgen.h"
  64 #endif
  65
  66 /*----- Data structures ---------------------------------------------------*/
  67
  68 /* --- The parameters and keys are the same as for Diffie-Hellman --- */
  69
  70 typedef dh_param dsa_param;
  71 typedef dh_pub dsa_pub;
  72 typedef dh_priv dsa_priv;
  73
  74 /* --- DSA key seed structure --- */
  75
  76 typedef struct dsa_seed {
  77   void *p;                              /* Pointer to seed material */
  78   size_t sz;                            /* Size of seed material */
  79   unsigned count;                       /* Iterations to find @p@ */
  80 } dsa_seed;
  81
  82 /* --- DSA signature structure --- *
  83  *
  84  * This is the recommended structure for a DSA signature.  The actual signing
  85  * function can cope with arbitrary-sized objects given appropriate
  86  * parameters, however.
  87  */
  88
  89 #define DSA_SIGLEN 20
  90
  91 typedef struct dsa_sig {
  92   octet r[DSA_SIGLEN];                  /* 160-bit @r@ value */
  93   octet s[DSA_SIGLEN];                  /* 160-bit @s@ value */
  94 } dsa_sig;
  95
  96 /*----- Key fetching ------------------------------------------------------*/
  97
  98 #define dsa_paramfetch dh_paramfetch
  99 #define dsa_pubfetch dh_pubfetch
 100 #define dsa_privfetch dh_privfetch
 101
 102 #define DSA_PARAMFETCHSZ DH_PARAMFETCHSZ
 103 #define DSA_PUBFETCHSZ DH_PUBFETCHSZ
 104 #define DSA_PRIVFETCHSZ DH_PRIVFETCHSZ
 105
 106 #define dsa_paramfree dh_paramfree
 107 #define dsa_pubfree dh_pubfree
 108 #define dsa_privfree dh_privfree
 109
 110 /*----- DSA stepper -------------------------------------------------------*/
 111
 112 typedef struct dsa_stepctx {
 113
 114   /* --- To be initialized by the client --- */
 115
 116   grand *r;                             /* Random number generator */
 117   mp *q;                                /* Force @p@ to be a multiple */
 118   size_t bits;                          /* Number of bits in the result */
 119   unsigned or;                          /* OR mask for low order bits */
 120   unsigned count;                       /* Counts the number of steps made */
 121   void *seedbuf;                        /* Pointer to seed buffer */
 122 } dsa_stepctx;
 123
 124 /* --- @dsa_step@ --- *
 125  *
 126  * The stepper chooses random integers, ensures that they are a multiple of
 127  * @q@ (if specified), sets the low-order bits, and then tests for
 128  * divisibility by small primes.
 129  */
 130
 131 extern pgen_proc dsa_step;
 132
 133 /*----- Functions provided ------------------------------------------------*/
 134
 135 /* --- @dsa_gen@ --- *
 136  *
 137  * Arguments:   @dsa_param *dp@ = where to store parameters
 138  *              @unsigned ql@ = length of @q@ in bits
 139  *              @unsigned pl@ = length of @p@ in bits
 140  *              @unsigned steps@ = number of steps to find @q@
 141  *              @const void *k@ = pointer to key material
 142  *              @size_t sz@ = size of key material
 143  *              @dsa_seed *sd@ = optional pointer for output seed information
 144  *              @pgen_proc *event@ = event handler function
 145  *              @void *ectx@ = argument for event handler
 146  *
 147  * Returns:     @PGEN_DONE@ if everything worked ok; @PGEN_ABORT@ otherwise.
 148  *
 149  * Use:         Generates the DSA shared parameters from a given seed value.
 150  *              This can take quite a long time.
 151  *
 152  *              The algorithm used is a compatible extension of the method
 153  *              described in the DSA standard, FIPS 186.  The standard
 154  *              requires that %$q$% be 160 bits in size (i.e., @ql == 160@)
 155  *              and that the length of %$p$% be %$L = 512 + 64l$% for some
 156  *              %$l$%.  Neither limitation applies to this implementation.
 157  */
 158
 159 extern int dsa_gen(dsa_param */*dp*/, unsigned /*ql*/, unsigned /*pl*/,
 160                    unsigned /*steps*/, const void */*k*/, size_t /*sz*/,
 161                    dsa_seed */*sd*/, pgen_proc */*event*/, void */*ectx*/);
 162
 163 /* --- @dsa_checkparam@ --- *
 164  *
 165  * Arguments:   @keycheck *kc@ = keycheck state
 166  *              @const dsa_param *dp@ = pointer to the parameter set
 167  *              @const dsa_seed *ds@ = pointer to seed information
 168  *
 169  * Returns:     Zero if all OK, or return status from function.
 170  *
 171  * Use:         Checks a set of DSA parameters for consistency and security.
 172  */
 173
 174 extern int dsa_checkparam(keycheck */*kc*/, const dsa_param */*dp*/,
 175                           const dsa_seed */*ds*/);
 176
 177 /* --- @dsa_h2n@ --- *
 178  *
 179  * Arguments:   @mp *d@ = destination integer
 180  *              @mp *r@ = order of the DSA group
 181  *              @const void *h@ = pointer to message hash
 182  *              @size_t hsz@ = size (in bytes) of the hash output
 183  *
 184  * Returns:     Resulting integer.
 185  *
 186  * Use:         Converts a hash to an integer in the demented way necessary
 187  *              for DSA/ECDSA.  This is, of course, completely insane, but
 188  *              there you go.
 189  */
 190
 191 extern mp *dsa_h2n(mp */*d*/, mp */*r*/, const void */*h*/, size_t /*hsz*/);
 192
 193 /* --- @dsa_nonce@ --- *
 194  *
 195  * Arguments:   @mp *d@ = destination integer
 196  *              @mp *q@ = order of the DSA group
 197  *              @mp *x@ = secret key
 198  *              @const octet *m@ = message hash
 199  *              @const gchash *ch@ = hash class
 200  *              @grand *r@ = random bit source, or null
 201  *
 202  * Returns:     A nonce.
 203  *
 204  * Use:         Generates a nonce for use in DSA (or another Fiat--Shamir
 205  *              signature scheme).
 206  */
 207
 208 extern mp *dsa_nonce(mp */*d*/, mp */*q*/, mp */*x*/, const octet */*m*/,
 209                      const gchash */*ch*/, grand */*r*/);
 210
 211 /* --- @dsa_mksig@ --- *
 212  *
 213  * Arguments:   @const dsa_param *dp@ = pointer to DSA parameters
 214  *              @mp *a@ = secret signing key
 215  *              @mp *m@ = message to be signed
 216  *              @mp *k@ = random data
 217  *              @mp **rr, **ss@ = where to put output parameters
 218  *
 219  * Returns:     ---
 220  *
 221  * Use:         Computes a DSA signature of a message.
 222  */
 223
 224 extern void dsa_mksig(const dsa_param */*dp*/, mp */*a*/,
 225                       mp */*m*/, mp */*k*/,
 226                       mp **/*rr*/, mp **/*ss*/);
 227
 228 /* --- @dsa_sign@ --- *
 229  *
 230  * Arguments:   @dsa_param *dp@ = pointer to DSA parameters
 231  *              @mp *a@ = pointer to secret signing key
 232  *              @const void *m@ = pointer to message
 233  *              @size_t msz@ = size of the message
 234  *              @const void *k@ = secret random data for securing signature
 235  *              @size_t ksz@ = size of secret data
 236  *              @void *r@ = pointer to output space for @r@
 237  *              @size_t rsz@ = size of output space for @r@
 238  *              @void *s@ = pointer to output space for @s@
 239  *              @size_t ssz@ = size of output space for @s@
 240  *
 241  * Returns:     ---
 242  *
 243  * Use:         Signs a message, storing the results in a big-endian binary
 244  *              form.
 245  */
 246
 247 extern void dsa_sign(dsa_param */*dp*/, mp */*a*/,
 248                      const void */*m*/, size_t /*msz*/,
 249                      const void */*k*/, size_t /*ksz*/,
 250                      void */*r*/, size_t /*rsz*/,
 251                      void */*s*/, size_t /*ssz*/);
 252
 253 /* --- @dsa_vrfy@ --- *
 254  *
 255  * Arguments:   @const dsa_param *dp@ = pointer to DSA parameters
 256  *              @mp *y@ = public verification key
 257  *              @mp *m@ = message which was signed
 258  *              @mp *r, *s@ = the signature
 259  *
 260  * Returns:     Zero if the signature is a forgery, nonzero if it's valid.
 261  *
 262  * Use:         Verifies a DSA digital signature.
 263  */
 264
 265 extern int dsa_vrfy(const dsa_param */*dp*/, mp */*y*/,
 266                     mp */*m*/, mp */*r*/, mp */*s*/);
 267
 268 /* --- @dsa_verify@ --- *
 269  *
 270  * Arguments:   @const dsa_param *dp@ = pointer to DSA parameters
 271  *              @mp *y@ = public verification key
 272  *              @const void *m@ = pointer to message block
 273  *              @size_t msz@ = size of message block
 274  *              @const void *r@ = pointer to @r@ signature half
 275  *              @size_t rsz@ = size of @r@
 276  *              @const void *s@ = pointer to @s@ signature half
 277  *              @size_t ssz@ = size of @s@
 278  *
 279  * Returns:     Zero if the signature is a forgery, nonzero if it's valid.
 280  *
 281  * Use:         Verifies a DSA digital signature.
 282  */
 283
 284 extern int dsa_verify(const dsa_param */*dp*/, mp */*y*/,
 285                       const void */*m*/, size_t /*msz*/,
 286                       const void */*r*/, size_t /*rsz*/,
 287                       const void */*s*/, size_t /*ssz*/);
 288
 289 /*----- That's all, folks -------------------------------------------------*/
 290
 291 #ifdef __cplusplus
 292   }
 293 #endif
 294
 295 #endif