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

   1 /* -*-c-*-
   2  *
   3  * Block cipher counter mode (or long cycle mode)
   4  *
   5  * (c) 2000 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_COUNTER_H
  29 #define CATACOMB_COUNTER_H
  30
  31 #ifdef __cplusplus
  32   extern "C" {
  33 #endif
  34
  35 /*----- Header files ------------------------------------------------------*/
  36
  37 #include <stddef.h>
  38
  39 #include <mLib/bits.h>
  40
  41 #ifndef CATACOMB_GCIPHER_H
  42 #  include "gcipher.h"
  43 #endif
  44
  45 #ifndef CATACOMB_GRAND_H
  46 #  include "grand.h"
  47 #endif
  48
  49 /*----- Macros ------------------------------------------------------------*/
  50
  51 /* --- @COUNTER_DECL@ --- *
  52  *
  53  * Arguments:   @PRE@, @pre@ = prefixes for block cipher definitions
  54  *
  55  * Use:         Makes declarations for counter mode.
  56  */
  57
  58 #define COUNTER_DECL(PRE, pre)                                          \
  59                                                                         \
  60 /* --- Counter mode context --- */                                      \
  61                                                                         \
  62 typedef struct pre##_counterctx {                                       \
  63   pre##_ctx ctx;                        /* Underlying cipher context */ \
  64   unsigned off;                         /* Current offset in buffer */  \
  65   octet b[PRE##_BLKSZ];                 /* Output buffer */             \
  66   uint32 c[PRE##_BLKSZ / 4];            /* Counter */                   \
  67 } pre##_counterctx;                                                     \
  68                                                                         \
  69 /* --- @pre_countergetiv@ --- *                                         \
  70  *                                                                      \
  71  * Arguments:   @const pre_counterctx *ctx@ = pointer to counter        \
  72  *                      context                                         \
  73  *              @void *iv@ = pointer to output data block               \
  74  *                                                                      \
  75  * Returns:     ---                                                     \
  76  *                                                                      \
  77  * Use:         Reads the currently set IV.  Reading and setting an IV  \
  78  *              is not transparent to the cipher.  It will add a `step' \
  79  *              which must be matched by a similar operation during     \
  80  *              decryption.                                             \
  81  */                                                                     \
  82                                                                         \
  83 extern void pre##_countergetiv(const pre##_counterctx */*ctx*/,         \
  84                                void */*iv*/);                           \
  85                                                                         \
  86 /* --- @pre_countersetiv@ --- *                                         \
  87  *                                                                      \
  88  * Arguments:   @pre_counterctx *ctx@ = pointer to counter context      \
  89  *              @cnost void *iv@ = pointer to IV to set                 \
  90  *                                                                      \
  91  * Returns:     ---                                                     \
  92  *                                                                      \
  93  * Use:         Sets the IV to use for subsequent encryption.           \
  94  */                                                                     \
  95                                                                         \
  96 extern void pre##_countersetiv(pre##_counterctx */*ctx*/,               \
  97                                const void */*iv*/);                     \
  98                                                                         \
  99 /* --- @pre_counterbdry@ --- *                                          \
 100  *                                                                      \
 101  * Arguments:   @pre_counterctx *ctx@ = pointer to counter context      \
 102  *                                                                      \
 103  * Returns:     ---                                                     \
 104  *                                                                      \
 105  * Use:         Inserts a boundary during encryption.  Successful       \
 106  *              decryption must place a similar boundary.               \
 107  */                                                                     \
 108                                                                         \
 109 extern void pre##_counterbdry(pre##_counterctx */*ctx*/);               \
 110                                                                         \
 111 /* --- @pre_countersetkey@ --- *                                        \
 112  *                                                                      \
 113  * Arguments:   @pre_counterctx *ctx@ = pointer to counter context      \
 114  *              @const pre_ctx *k@ = pointer to cipher context          \
 115  *                                                                      \
 116  * Returns:     ---                                                     \
 117  *                                                                      \
 118  * Use:         Sets the counter context to use a different cipher key. \
 119  */                                                                     \
 120                                                                         \
 121 extern void pre##_countersetkey(pre##_counterctx */*ctx*/,              \
 122                                 const pre##_ctx */*k*/);                \
 123                                                                         \
 124 /* --- @pre_counterinit@ --- *                                          \
 125  *                                                                      \
 126  * Arguments:   @pre_counterctx *ctx@ = pointer to cipher context       \
 127  *              @const void *key@ = pointer to the key buffer           \
 128  *              @size_t sz@ = size of the key                           \
 129  *              @const void *iv@ = pointer to initialization vector     \
 130  *                                                                      \
 131  * Returns:     ---                                                     \
 132  *                                                                      \
 133  * Use:         Initializes a counter context ready for use.  You       \
 134  *              should ensure that the IV chosen is unique: reusing an  \
 135  *              IV will compromise the security of the entire           \
 136  *              plaintext.  This is equivalent to calls to @pre_init@,  \
 137  *              @pre_countersetkey@ and @pre_countersetiv@.             \
 138  */                                                                     \
 139                                                                         \
 140 extern void pre##_counterinit(pre##_counterctx */*ctx*/,                \
 141                               const void */*key*/, size_t /*sz*/,       \
 142                               const void */*iv*/);                      \
 143                                                                         \
 144 /* --- @pre_counterencrypt@ --- *                                       \
 145  *                                                                      \
 146  * Arguments:   @pre_counterctx *ctx@ = pointer to counter context      \
 147  *              @const void *src@ = pointer to source data              \
 148  *              @void *dest@ = pointer to destination data              \
 149  *              @size_t sz@ = size of block to be encrypted             \
 150  *                                                                      \
 151  * Returns:     ---                                                     \
 152  *                                                                      \
 153  * Use:         Encrypts or decrypts a block with a block cipher in     \
 154  *              counter mode: encryption and decryption are the same in \
 155  *              counter.  The destination may be null to just churn the \
 156  *              feedback round for a bit.  The source may be null to    \
 157  *              use the cipher as a random data generator.              \
 158  */                                                                     \
 159                                                                         \
 160 extern void pre##_counterencrypt(pre##_counterctx */*ctx*/,             \
 161                                  const void */*src*/, void */*dest*/,   \
 162                                  size_t /*sz*/);                        \
 163                                                                         \
 164 /* --- @pre_counterrand@ --- *                                          \
 165  *                                                                      \
 166  * Arguments:   @const void *k@ = pointer to key material               \
 167  *              @size_t sz@ = size of key material                      \
 168  *                                                                      \
 169  * Returns:     Pointer to generic random number generator interface.   \
 170  *                                                                      \
 171  * Use:         Creates a random number interface wrapper around an     \
 172  *              counter-mode block cipher.                              \
 173  */                                                                     \
 174                                                                         \
 175 extern grand *pre##_counterrand(const void */*k*/, size_t /*sz*/);      \
 176                                                                         \
 177 /* --- Generic cipher interface --- */                                  \
 178                                                                         \
 179 extern const gccipher pre##_counter;
 180
 181 /*----- That's all, folks -------------------------------------------------*/
 182
 183 #ifdef __cplusplus
 184   }
 185 #endif
 186
 187 #endif