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

   1 /* -*-c-*-
   2  *
   3  * Random number generator for DSA
   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_DSARAND_H
  29 #define CATACOMB_DSARAND_H
  30
  31 #ifdef __cplusplus
  32   extern "C" {
  33 #endif
  34
  35 /*----- Header files ------------------------------------------------------*/
  36
  37 #include <mLib/bits.h>
  38
  39 #ifndef CATACOMB_GRAND_H
  40 #  include "grand.h"
  41 #endif
  42
  43 #ifndef CATACOMB_SHA_H
  44 #  include "sha.h"
  45 #endif
  46
  47 /*----- Data structures ---------------------------------------------------*/
  48
  49 typedef struct dsarand {
  50   octet *p;                             /* Pointer to seed (modified) */
  51   size_t sz;                            /* Size of the seed buffer */
  52   unsigned passes;                      /* Number of passes to make */
  53 } dsarand;
  54
  55 /*----- Functions provided ------------------------------------------------*/
  56
  57 /* --- @dsarand_init@ --- *
  58  *
  59  * Arguments:   @dsarand *d@ = pointer to context
  60  *              @const void *p@ = pointer to seed buffer
  61  *              @size_t sz@ = size of the buffer
  62  *
  63  * Returns:     ---
  64  *
  65  * Use:         Initializes a DSA random number generator.
  66  */
  67
  68 extern void dsarand_init(dsarand */*d*/, const void */*p*/, size_t /*sz*/);
  69
  70 /* --- @dsarand_reseed@ --- *
  71  *
  72  * Arguments:   @dsarand *d@ = pointer to context
  73  *              @const void *p@ = pointer to seed buffer
  74  *              @size_t sz@ = size of the buffer
  75  *
  76  * Returns:     ---
  77  *
  78  * Use:         Initializes a DSA random number generator.
  79  */
  80
  81 extern void dsarand_reseed(dsarand */*d*/, const void */*p*/, size_t /*sz*/);
  82
  83 /* --- @dsarand_destroy@ --- *
  84  *
  85  * Arguments:   @dsarand *d@ = pointer to context
  86  *
  87  * Returns:     ---
  88  *
  89  * Use:         Disposes of a DSA random number generation context.
  90  */
  91
  92 extern void dsarand_destroy(dsarand */*d*/);
  93
  94 /* --- @dsarand_fill@ --- *
  95  *
  96  * Arguments:   @dsarand *d@ = pointer to context
  97  *              @void *p@ = pointer to output buffer
  98  *              @size_t sz@ = size of output buffer
  99  *
 100  * Returns:     ---
 101  *
 102  * Use:         Fills an output buffer with pseudorandom data.
 103  *
 104  *              Let %$p$% be the numerical value of the input buffer, and let
 105  *              %$b$% be the number of bytes required.  Let
 106  *              %$z = \lceil b / 20 \rceil$% be the number of SHA outputs
 107  *              required.  Then the output of pass %$n$% is
 108  *
 109  *                %$P_n = \sum_{0 \le i < z} 2^{160i} SHA(p + nz + i)$%
 110  *                                                      %${} \bmod 2^{8b}$%
 111  *
 112  *              and the actual result in the output buffer is the XOR of all
 113  *              of the output passes.
 114  *
 115  *              The DSA procedure for choosing @q@ involves two passes with
 116  *              %$z = 1$%; the procedure for choosing @p@ involves one pass
 117  *              with larger %$z$%.  This generalization of the DSA generation
 118  *              procedure is my own invention but it seems relatively sound.
 119  */
 120
 121 extern void dsarand_fill(dsarand */*d*/, void */*p*/, size_t /*sz*/);
 122
 123 /*----- Generic pseudorandom-number generator interface -------------------*/
 124
 125 /* --- Miscellaneous operations --- */
 126
 127 enum {
 128   DSARAND_PASSES = GRAND_SPECIFIC('D'), /* @unsigned n@ */
 129   DSARAND_SEEDSZ,                       /* No args */
 130   DSARAND_GETSEED                       /* @void *buf@ */
 131 };
 132
 133 /* --- @dsarand_create@ --- *
 134  *
 135  * Arguments:   @const void *p@ = pointer to seed buffer
 136  *              @size_t sz@ = size of seed buffer
 137  *
 138  * Returns:     Pointer to a generic generator.
 139  *
 140  * Use:         Constructs a generic generator interface to a DSA generator.
 141  */
 142
 143 extern grand *dsarand_create(const void */*p*/, size_t /*sz*/);
 144
 145 /*----- That's all, folks -------------------------------------------------*/
 146
 147 #ifdef __cplusplus
 148   }
 149 #endif
 150
 151 #endif