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

   1 /* -*-c-*-
   2  *
   3  * $Id: ofb.h,v 1.3 2000/06/17 11:48:24 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 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: ofb.h,v $
  33  * Revision 1.3  2000/06/17 11:48:24  mdw
  34  * Change buffer offset to be unsigned.
  35  *
  36  * Revision 1.2  1999/12/10 23:16:40  mdw
  37  * Split mode macros into interface and implementation.
  38  *
  39  * Revision 1.1  1999/09/03 08:41:12  mdw
  40  * Initial import.
  41  *
  42  */
  43
  44 #ifndef CATACOMB_OFB_H
  45 #define CATACOMB_OFB_H
  46
  47 #ifdef __cplusplus
  48   extern "C" {
  49 #endif
  50
  51 /*----- Header files ------------------------------------------------------*/
  52
  53 #include <stddef.h>
  54
  55 #include <mLib/bits.h>
  56
  57 #ifndef CATACOMB_GCIPHER_H
  58 #  include "gcipher.h"
  59 #endif
  60
  61 #ifndef CATACOMB_GRAND_H
  62 #  include "grand.h"
  63 #endif
  64
  65 /*----- Macros ------------------------------------------------------------*/
  66
  67 /* --- @OFB_DECL@ --- *
  68  *
  69  * Arguments:   @PRE@, @pre@ = prefixes for block cipher definitions
  70  *
  71  * Use:         Makes declarations for output feedback mode.
  72  */
  73
  74 #define OFB_DECL(PRE, pre)                                              \
  75                                                                         \
  76 /* --- Output feedback context --- */                                   \
  77                                                                         \
  78 typedef struct pre##_ofbctx {                                           \
  79   pre##_ctx ctx;                        /* Underlying cipher context */ \
  80   unsigned off;                         /* Current offset in buffer */  \
  81   octet iv[PRE##_BLKSZ];                /* Output buffer and IV */      \
  82 } pre##_ofbctx;                                                         \
  83                                                                         \
  84 /* --- @pre_ofbgetiv@ --- *                                             \
  85  *                                                                      \
  86  * Arguments:   @const pre_ofbctx *ctx@ = pointer to OFB context block  \
  87  *              @void *iv#@ = pointer to output data block              \
  88  *                                                                      \
  89  * Returns:     ---                                                     \
  90  *                                                                      \
  91  * Use:         Reads the currently set IV.  Reading and setting an IV  \
  92  *              is not transparent to the cipher.  It will add a `step' \
  93  *              which must be matched by a similar operation during     \
  94  *              decryption.                                             \
  95  */                                                                     \
  96                                                                         \
  97 extern void pre##_ofbgetiv(const pre##_ofbctx */*ctx*/,                 \
  98                            void */*iv*/);                               \
  99                                                                         \
 100 /* --- @pre_ofbsetiv@ --- *                                             \
 101  *                                                                      \
 102  * Arguments:   @pre_ofbctx *ctx@ = pointer to OFB context block        \
 103  *              @cnost void *iv@ = pointer to IV to set                 \
 104  *                                                                      \
 105  * Returns:     ---                                                     \
 106  *                                                                      \
 107  * Use:         Sets the IV to use for subsequent encryption.           \
 108  */                                                                     \
 109                                                                         \
 110 extern void pre##_ofbsetiv(pre##_ofbctx */*ctx*/,                       \
 111                            const void */*iv*/);                         \
 112                                                                         \
 113 /* --- @pre_ofbbdry@ --- *                                              \
 114  *                                                                      \
 115  * Arguments:   @pre_ofbctx *ctx@ = pointer to OFB context block        \
 116  *                                                                      \
 117  * Returns:     ---                                                     \
 118  *                                                                      \
 119  * Use:         Inserts a boundary during encryption.  Successful       \
 120  *              decryption must place a similar boundary.               \
 121  */                                                                     \
 122                                                                         \
 123 extern void pre##_ofbbdry(pre##_ofbctx */*ctx*/);                       \
 124                                                                         \
 125 /* --- @pre_ofbsetkey@ --- *                                            \
 126  *                                                                      \
 127  * Arguments:   @pre_ofbctx *ctx@ = pointer to OFB context block        \
 128  *              @const pre_ctx *k@ = pointer to cipher context          \
 129  *                                                                      \
 130  * Returns:     ---                                                     \
 131  *                                                                      \
 132  * Use:         Sets the OFB context to use a different cipher key.     \
 133  */                                                                     \
 134                                                                         \
 135 extern void pre##_ofbsetkey(pre##_ofbctx */*ctx*/,                      \
 136                             const pre##_ctx */*k*/);                    \
 137                                                                         \
 138 /* --- @pre_ofbinit@ --- *                                              \
 139  *                                                                      \
 140  * Arguments:   @pre_ofbctx *ctx@ = pointer to cipher context           \
 141  *              @const void *key@ = pointer to the key buffer           \
 142  *              @size_t sz@ = size of the key                           \
 143  *              @const void *iv@ = pointer to initialization vector     \
 144  *                                                                      \
 145  * Returns:     ---                                                     \
 146  *                                                                      \
 147  * Use:         Initializes a OFB context ready for use.  You should    \
 148  *              ensure that the IV chosen is unique: reusing an IV will \
 149  *              compromise the security of the entire plaintext.  This  \
 150  *              is equivalent to calls to @pre_init@, @pre_ofbsetkey@   \
 151  *              and @pre_ofbsetiv@.                                     \
 152  */                                                                     \
 153                                                                         \
 154 extern void pre##_ofbinit(pre##_ofbctx */*ctx*/,                        \
 155                           const void */*key*/, size_t /*sz*/,           \
 156                           const void */*iv*/);                          \
 157                                                                         \
 158 /* --- @pre_ofbencrypt@ --- *                                           \
 159  *                                                                      \
 160  * Arguments:   @pre_ofbctx *ctx@ = pointer to OFB context block        \
 161  *              @const void *src@ = pointer to source data              \
 162  *              @void *dest@ = pointer to destination data              \
 163  *              @size_t sz@ = size of block to be encrypted             \
 164  *                                                                      \
 165  * Returns:     ---                                                     \
 166  *                                                                      \
 167  * Use:         Encrypts or decrypts a block with a block cipher in OFB \
 168  *              mode: encryption and decryption are the same in OFB.    \
 169  *              The destination may be null to just churn the feedback  \
 170  *              round for a bit.  The source may be null to use the     \
 171  *              cipher as a random data generator.                      \
 172  */                                                                     \
 173                                                                         \
 174 extern void pre##_ofbencrypt(pre##_ofbctx */*ctx*/,                     \
 175                              const void */*src*/, void */*dest*/,       \
 176                              size_t /*sz*/);                            \
 177                                                                         \
 178 /* --- @pre_ofbrand@ --- *                                              \
 179  *                                                                      \
 180  * Arguments:   @const void *k@ = pointer to key material               \
 181  *              @size_t sz@ = size of key material                      \
 182  *                                                                      \
 183  * Returns:     Pointer to generic random number generator interface.   \
 184  *                                                                      \
 185  * Use:         Creates a random number interface wrapper around an     \
 186  *              OFB-mode block cipher.                                  \
 187  */                                                                     \
 188                                                                         \
 189 extern grand *pre##_ofbrand(const void */*k*/, size_t /*sz*/);          \
 190                                                                         \
 191 /* --- Generic cipher interface --- */                                  \
 192                                                                         \
 193 extern const gccipher pre##_ofb;
 194
 195 /*----- That's all, folks -------------------------------------------------*/
 196
 197 #ifdef __cplusplus
 198   }
 199 #endif
 200
 201 #endif