chiark - git - mdw - catacomb/blob - counter.h

   1 /* -*-c-*-
   2  *
   3  * $Id: counter.h,v 1.4 2004/04/08 01:36:15 mdw Exp $
   4  *
   5  * Block cipher counter mode (or long cycle mode)
   6  *
   7  * (c) 2000 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 #ifndef CATACOMB_COUNTER_H
  31 #define CATACOMB_COUNTER_H
  32
  33 #ifdef __cplusplus
  34   extern "C" {
  35 #endif
  36
  37 /*----- Header files ------------------------------------------------------*/
  38
  39 #include <stddef.h>
  40
  41 #include <mLib/bits.h>
  42
  43 #ifndef CATACOMB_GCIPHER_H
  44 #  include "gcipher.h"
  45 #endif
  46
  47 #ifndef CATACOMB_GRAND_H
  48 #  include "grand.h"
  49 #endif
  50
  51 /*----- Macros ------------------------------------------------------------*/
  52
  53 /* --- @COUNTER_DECL@ --- *
  54  *
  55  * Arguments:   @PRE@, @pre@ = prefixes for block cipher definitions
  56  *
  57  * Use:         Makes declarations for counter mode.
  58  */
  59
  60 #define COUNTER_DECL(PRE, pre)                                          \
  61                                                                         \
  62 /* --- Counter mode context --- */                                      \
  63                                                                         \
  64 typedef struct pre##_counterctx {                                       \
  65   pre##_ctx ctx;                        /* Underlying cipher context */ \
  66   unsigned off;                         /* Current offset in buffer */  \
  67   octet buf[PRE##_BLKSZ];               /* Output buffer */             \
  68   uint32 n[PRE##_BLKSZ / 4];            /* Counter */                   \
  69 } pre##_counterctx;                                                     \
  70                                                                         \
  71 /* --- @pre_countergetiv@ --- *                                         \
  72  *                                                                      \
  73  * Arguments:   @const pre_counterctx *ctx@ = pointer to counter        \
  74  *                      context                                         \
  75  *              @void *iv@ = pointer to output data block               \
  76  *                                                                      \
  77  * Returns:     ---                                                     \
  78  *                                                                      \
  79  * Use:         Reads the currently set IV.  Reading and setting an IV  \
  80  *              is not transparent to the cipher.  It will add a `step' \
  81  *              which must be matched by a similar operation during     \
  82  *              decryption.                                             \
  83  */                                                                     \
  84                                                                         \
  85 extern void pre##_countergetiv(const pre##_counterctx */*ctx*/,         \
  86                                void */*iv*/);                           \
  87                                                                         \
  88 /* --- @pre_countersetiv@ --- *                                         \
  89  *                                                                      \
  90  * Arguments:   @pre_counterctx *ctx@ = pointer to counter context      \
  91  *              @cnost void *iv@ = pointer to IV to set                 \
  92  *                                                                      \
  93  * Returns:     ---                                                     \
  94  *                                                                      \
  95  * Use:         Sets the IV to use for subsequent encryption.           \
  96  */                                                                     \
  97                                                                         \
  98 extern void pre##_countersetiv(pre##_counterctx */*ctx*/,               \
  99                                const void */*iv*/);                     \
 100                                                                         \
 101 /* --- @pre_counterbdry@ --- *                                          \
 102  *                                                                      \
 103  * Arguments:   @pre_counterctx *ctx@ = pointer to counter context      \
 104  *                                                                      \
 105  * Returns:     ---                                                     \
 106  *                                                                      \
 107  * Use:         Inserts a boundary during encryption.  Successful       \
 108  *              decryption must place a similar boundary.               \
 109  */                                                                     \
 110                                                                         \
 111 extern void pre##_counterbdry(pre##_counterctx */*ctx*/);               \
 112                                                                         \
 113 /* --- @pre_countersetkey@ --- *                                        \
 114  *                                                                      \
 115  * Arguments:   @pre_counterctx *ctx@ = pointer to counter context      \
 116  *              @const pre_ctx *k@ = pointer to cipher context          \
 117  *                                                                      \
 118  * Returns:     ---                                                     \
 119  *                                                                      \
 120  * Use:         Sets the counter context to use a different cipher key. \
 121  */                                                                     \
 122                                                                         \
 123 extern void pre##_countersetkey(pre##_counterctx */*ctx*/,              \
 124                                 const pre##_ctx */*k*/);                \
 125                                                                         \
 126 /* --- @pre_counterinit@ --- *                                          \
 127  *                                                                      \
 128  * Arguments:   @pre_counterctx *ctx@ = pointer to cipher context       \
 129  *              @const void *key@ = pointer to the key buffer           \
 130  *              @size_t sz@ = size of the key                           \
 131  *              @const void *iv@ = pointer to initialization vector     \
 132  *                                                                      \
 133  * Returns:     ---                                                     \
 134  *                                                                      \
 135  * Use:         Initializes a counter context ready for use.  You       \
 136  *              should ensure that the IV chosen is unique: reusing an  \
 137  *              IV will compromise the security of the entire           \
 138  *              plaintext.  This is equivalent to calls to @pre_init@,  \
 139  *              @pre_countersetkey@ and @pre_countersetiv@.             \
 140  */                                                                     \
 141                                                                         \
 142 extern void pre##_counterinit(pre##_counterctx */*ctx*/,                \
 143                               const void */*key*/, size_t /*sz*/,       \
 144                               const void */*iv*/);                      \
 145                                                                         \
 146 /* --- @pre_counterencrypt@ --- *                                       \
 147  *                                                                      \
 148  * Arguments:   @pre_counterctx *ctx@ = pointer to counter context      \
 149  *              @const void *src@ = pointer to source data              \
 150  *              @void *dest@ = pointer to destination data              \
 151  *              @size_t sz@ = size of block to be encrypted             \
 152  *                                                                      \
 153  * Returns:     ---                                                     \
 154  *                                                                      \
 155  * Use:         Encrypts or decrypts a block with a block cipher in     \
 156  *              counter mode: encryption and decryption are the same in \
 157  *              counter.  The destination may be null to just churn the \
 158  *              feedback round for a bit.  The source may be null to    \
 159  *              use the cipher as a random data generator.              \
 160  */                                                                     \
 161                                                                         \
 162 extern void pre##_counterencrypt(pre##_counterctx */*ctx*/,             \
 163                                  const void */*src*/, void */*dest*/,   \
 164                                  size_t /*sz*/);                        \
 165                                                                         \
 166 /* --- @pre_counterrand@ --- *                                          \
 167  *                                                                      \
 168  * Arguments:   @const void *k@ = pointer to key material               \
 169  *              @size_t sz@ = size of key material                      \
 170  *                                                                      \
 171  * Returns:     Pointer to generic random number generator interface.   \
 172  *                                                                      \
 173  * Use:         Creates a random number interface wrapper around an     \
 174  *              counter-mode block cipher.                              \
 175  */                                                                     \
 176                                                                         \
 177 extern grand *pre##_counterrand(const void */*k*/, size_t /*sz*/);      \
 178                                                                         \
 179 /* --- Generic cipher interface --- */                                  \
 180                                                                         \
 181 extern const gccipher pre##_counter;
 182
 183 /*----- That's all, folks -------------------------------------------------*/
 184
 185 #ifdef __cplusplus
 186   }
 187 #endif
 188
 189 #endif