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

   1 /* -*-c-*-
   2  *
   3  * $Id: ofb.h,v 1.5 2004/04/08 01:36:15 mdw Exp $
   4  *
   5  * Output feedback for block ciphers
   6  *
   7  * (c) 1999 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_OFB_H
  31 #define CATACOMB_OFB_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 /* --- @OFB_DECL@ --- *
  54  *
  55  * Arguments:   @PRE@, @pre@ = prefixes for block cipher definitions
  56  *
  57  * Use:         Makes declarations for output feedback mode.
  58  */
  59
  60 #define OFB_DECL(PRE, pre)                                              \
  61                                                                         \
  62 /* --- Output feedback context --- */                                   \
  63                                                                         \
  64 typedef struct pre##_ofbctx {                                           \
  65   pre##_ctx ctx;                        /* Underlying cipher context */ \
  66   unsigned off;                         /* Current offset in buffer */  \
  67   octet iv[PRE##_BLKSZ];                /* Output buffer and IV */      \
  68 } pre##_ofbctx;                                                         \
  69                                                                         \
  70 /* --- @pre_ofbgetiv@ --- *                                             \
  71  *                                                                      \
  72  * Arguments:   @const pre_ofbctx *ctx@ = pointer to OFB context block  \
  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##_ofbgetiv(const pre##_ofbctx */*ctx*/,                 \
  84                            void */*iv*/);                               \
  85                                                                         \
  86 /* --- @pre_ofbsetiv@ --- *                                             \
  87  *                                                                      \
  88  * Arguments:   @pre_ofbctx *ctx@ = pointer to OFB context block        \
  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##_ofbsetiv(pre##_ofbctx */*ctx*/,                       \
  97                            const void */*iv*/);                         \
  98                                                                         \
  99 /* --- @pre_ofbbdry@ --- *                                              \
 100  *                                                                      \
 101  * Arguments:   @pre_ofbctx *ctx@ = pointer to OFB context block        \
 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##_ofbbdry(pre##_ofbctx */*ctx*/);                       \
 110                                                                         \
 111 /* --- @pre_ofbsetkey@ --- *                                            \
 112  *                                                                      \
 113  * Arguments:   @pre_ofbctx *ctx@ = pointer to OFB context block        \
 114  *              @const pre_ctx *k@ = pointer to cipher context          \
 115  *                                                                      \
 116  * Returns:     ---                                                     \
 117  *                                                                      \
 118  * Use:         Sets the OFB context to use a different cipher key.     \
 119  */                                                                     \
 120                                                                         \
 121 extern void pre##_ofbsetkey(pre##_ofbctx */*ctx*/,                      \
 122                             const pre##_ctx */*k*/);                    \
 123                                                                         \
 124 /* --- @pre_ofbinit@ --- *                                              \
 125  *                                                                      \
 126  * Arguments:   @pre_ofbctx *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 OFB context ready for use.  You should    \
 134  *              ensure that the IV chosen is unique: reusing an IV will \
 135  *              compromise the security of the entire plaintext.  This  \
 136  *              is equivalent to calls to @pre_init@, @pre_ofbsetkey@   \
 137  *              and @pre_ofbsetiv@.                                     \
 138  */                                                                     \
 139                                                                         \
 140 extern void pre##_ofbinit(pre##_ofbctx */*ctx*/,                        \
 141                           const void */*key*/, size_t /*sz*/,           \
 142                           const void */*iv*/);                          \
 143                                                                         \
 144 /* --- @pre_ofbencrypt@ --- *                                           \
 145  *                                                                      \
 146  * Arguments:   @pre_ofbctx *ctx@ = pointer to OFB context block        \
 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 OFB \
 154  *              mode: encryption and decryption are the same in OFB.    \
 155  *              The destination may be null to just churn the feedback  \
 156  *              round for a bit.  The source may be null to use the     \
 157  *              cipher as a random data generator.                      \
 158  */                                                                     \
 159                                                                         \
 160 extern void pre##_ofbencrypt(pre##_ofbctx */*ctx*/,                     \
 161                              const void */*src*/, void */*dest*/,       \
 162                              size_t /*sz*/);                            \
 163                                                                         \
 164 /* --- @pre_ofbrand@ --- *                                              \
 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  *              OFB-mode block cipher.                                  \
 173  */                                                                     \
 174                                                                         \
 175 extern grand *pre##_ofbrand(const void */*k*/, size_t /*sz*/);          \
 176                                                                         \
 177 /* --- Generic cipher interface --- */                                  \
 178                                                                         \
 179 extern const gccipher pre##_ofb;
 180
 181 /*----- That's all, folks -------------------------------------------------*/
 182
 183 #ifdef __cplusplus
 184   }
 185 #endif
 186
 187 #endif