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

   1 /* -*-c-*-
   2  *
   3  * Output feedback for block ciphers
   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_OFB_H
  29 #define CATACOMB_OFB_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 /* --- @OFB_DECL@ --- *
  52  *
  53  * Arguments:   @PRE@, @pre@ = prefixes for block cipher definitions
  54  *
  55  * Use:         Makes declarations for output feedback mode.
  56  */
  57
  58 #define OFB_DECL(PRE, pre)                                              \
  59                                                                         \
  60 /* --- Output feedback context --- */                                   \
  61                                                                         \
  62 typedef struct pre##_ofbctx {                                           \
  63   pre##_ctx ctx;                        /* Underlying cipher context */ \
  64   unsigned off;                         /* Current offset in buffer */  \
  65   octet b[PRE##_BLKSZ];                 /* Output buffer and IV */      \
  66 } pre##_ofbctx;                                                         \
  67                                                                         \
  68 /* --- @pre_ofbgetiv@ --- *                                             \
  69  *                                                                      \
  70  * Arguments:   @const pre_ofbctx *ctx@ = pointer to OFB context block  \
  71  *              @void *iv@ = pointer to output data block               \
  72  *                                                                      \
  73  * Returns:     ---                                                     \
  74  *                                                                      \
  75  * Use:         Reads the currently set IV.  Reading and setting an IV  \
  76  *              is not transparent to the cipher.  It will add a `step' \
  77  *              which must be matched by a similar operation during     \
  78  *              decryption.                                             \
  79  */                                                                     \
  80                                                                         \
  81 extern void pre##_ofbgetiv(const pre##_ofbctx */*ctx*/,                 \
  82                            void */*iv*/);                               \
  83                                                                         \
  84 /* --- @pre_ofbsetiv@ --- *                                             \
  85  *                                                                      \
  86  * Arguments:   @pre_ofbctx *ctx@ = pointer to OFB context block        \
  87  *              @cnost void *iv@ = pointer to IV to set                 \
  88  *                                                                      \
  89  * Returns:     ---                                                     \
  90  *                                                                      \
  91  * Use:         Sets the IV to use for subsequent encryption.           \
  92  */                                                                     \
  93                                                                         \
  94 extern void pre##_ofbsetiv(pre##_ofbctx */*ctx*/,                       \
  95                            const void */*iv*/);                         \
  96                                                                         \
  97 /* --- @pre_ofbbdry@ --- *                                              \
  98  *                                                                      \
  99  * Arguments:   @pre_ofbctx *ctx@ = pointer to OFB context block        \
 100  *                                                                      \
 101  * Returns:     ---                                                     \
 102  *                                                                      \
 103  * Use:         Inserts a boundary during encryption.  Successful       \
 104  *              decryption must place a similar boundary.               \
 105  */                                                                     \
 106                                                                         \
 107 extern void pre##_ofbbdry(pre##_ofbctx */*ctx*/);                       \
 108                                                                         \
 109 /* --- @pre_ofbsetkey@ --- *                                            \
 110  *                                                                      \
 111  * Arguments:   @pre_ofbctx *ctx@ = pointer to OFB context block        \
 112  *              @const pre_ctx *k@ = pointer to cipher context          \
 113  *                                                                      \
 114  * Returns:     ---                                                     \
 115  *                                                                      \
 116  * Use:         Sets the OFB context to use a different cipher key.     \
 117  */                                                                     \
 118                                                                         \
 119 extern void pre##_ofbsetkey(pre##_ofbctx */*ctx*/,                      \
 120                             const pre##_ctx */*k*/);                    \
 121                                                                         \
 122 /* --- @pre_ofbinit@ --- *                                              \
 123  *                                                                      \
 124  * Arguments:   @pre_ofbctx *ctx@ = pointer to cipher context           \
 125  *              @const void *key@ = pointer to the key buffer           \
 126  *              @size_t sz@ = size of the key                           \
 127  *              @const void *iv@ = pointer to initialization vector     \
 128  *                                                                      \
 129  * Returns:     ---                                                     \
 130  *                                                                      \
 131  * Use:         Initializes a OFB context ready for use.  You should    \
 132  *              ensure that the IV chosen is unique: reusing an IV will \
 133  *              compromise the security of the entire plaintext.  This  \
 134  *              is equivalent to calls to @pre_init@, @pre_ofbsetkey@   \
 135  *              and @pre_ofbsetiv@.                                     \
 136  */                                                                     \
 137                                                                         \
 138 extern void pre##_ofbinit(pre##_ofbctx */*ctx*/,                        \
 139                           const void */*key*/, size_t /*sz*/,           \
 140                           const void */*iv*/);                          \
 141                                                                         \
 142 /* --- @pre_ofbencrypt@ --- *                                           \
 143  *                                                                      \
 144  * Arguments:   @pre_ofbctx *ctx@ = pointer to OFB context block        \
 145  *              @const void *src@ = pointer to source data              \
 146  *              @void *dest@ = pointer to destination data              \
 147  *              @size_t sz@ = size of block to be encrypted             \
 148  *                                                                      \
 149  * Returns:     ---                                                     \
 150  *                                                                      \
 151  * Use:         Encrypts or decrypts a block with a block cipher in OFB \
 152  *              mode: encryption and decryption are the same in OFB.    \
 153  *              The destination may be null to just churn the feedback  \
 154  *              round for a bit.  The source may be null to use the     \
 155  *              cipher as a random data generator.                      \
 156  */                                                                     \
 157                                                                         \
 158 extern void pre##_ofbencrypt(pre##_ofbctx */*ctx*/,                     \
 159                              const void */*src*/, void */*dest*/,       \
 160                              size_t /*sz*/);                            \
 161                                                                         \
 162 /* --- @pre_ofbrand@ --- *                                              \
 163  *                                                                      \
 164  * Arguments:   @const void *k@ = pointer to key material               \
 165  *              @size_t sz@ = size of key material                      \
 166  *                                                                      \
 167  * Returns:     Pointer to generic random number generator interface.   \
 168  *                                                                      \
 169  * Use:         Creates a random number interface wrapper around an     \
 170  *              OFB-mode block cipher.                                  \
 171  */                                                                     \
 172                                                                         \
 173 extern grand *pre##_ofbrand(const void */*k*/, size_t /*sz*/);          \
 174                                                                         \
 175 /* --- Generic cipher interface --- */                                  \
 176                                                                         \
 177 extern const gccipher pre##_ofb;
 178
 179 /*----- That's all, folks -------------------------------------------------*/
 180
 181 #ifdef __cplusplus
 182   }
 183 #endif
 184
 185 #endif