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

   1 /* -*-c-*-
   2  *
   3  * Ciphertext 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_CFB_H
  29 #define CATACOMB_CFB_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 /*----- Data structures ---------------------------------------------------*/
  46
  47 /* --- @CFB_DECL@ --- *
  48  *
  49  * Arguments:   @PRE@, @pre@ = prefixes for the underlying block cipher
  50  *
  51  * Use:         Creates declarations for CFB mode.
  52  */
  53
  54 #define CFB_DECL(PRE, pre)                                              \
  55                                                                         \
  56 /* --- Ciphertext feedback context --- */                               \
  57                                                                         \
  58 typedef struct pre##_cfbctx {                                           \
  59   pre##_ctx ctx;                        /* Underlying cipher context */ \
  60   unsigned off;                         /* Offset into @iv@ buffer */   \
  61   octet iv[PRE##_BLKSZ];                /* Previous ciphertext or IV */ \
  62 } pre##_cfbctx;                                                         \
  63                                                                         \
  64 /* --- @pre_cfbgetiv@ --- *                                             \
  65  *                                                                      \
  66  * Arguments:   @const pre_cfbctx *ctx@ = pointer to CFB context block  \
  67  *              @void *iv@ = pointer to output data block               \
  68  *                                                                      \
  69  * Returns:     ---                                                     \
  70  *                                                                      \
  71  * Use:         Reads the currently set IV.  Reading and setting an IV  \
  72  *              is not transparent to the cipher.  It will add a `step' \
  73  *              which must be matched by a similar operation during     \
  74  *              decryption.                                             \
  75  */                                                                     \
  76                                                                         \
  77 extern void pre##_cfbgetiv(const pre##_cfbctx */*ctx*/,                 \
  78                            void */*iv*/);                               \
  79                                                                         \
  80 /* --- @pre_cfbsetiv@ --- *                                             \
  81  *                                                                      \
  82  * Arguments:   @pre_cfbctx *ctx@ = pointer to CFB context block        \
  83  *              @cnost void *iv@ = pointer to IV to set                 \
  84  *                                                                      \
  85  * Returns:     ---                                                     \
  86  *                                                                      \
  87  * Use:         Sets the IV to use for subsequent encryption.           \
  88  */                                                                     \
  89                                                                         \
  90 extern void pre##_cfbsetiv(pre##_cfbctx */*ctx*/,                       \
  91                            const void */*iv*/);                         \
  92                                                                         \
  93 /* --- @pre_cfbbdry@ --- *                                              \
  94  *                                                                      \
  95  * Arguments:   @pre_cfbctx *ctx@ = pointer to CFB context block        \
  96  *                                                                      \
  97  * Returns:     ---                                                     \
  98  *                                                                      \
  99  * Use:         Inserts a boundary during encryption.  Successful       \
 100  *              decryption must place a similar boundary.               \
 101  */                                                                     \
 102                                                                         \
 103 extern void pre##_cfbbdry(pre##_cfbctx */*ctx*/);                       \
 104                                                                         \
 105 /* --- @pre_cfbsetkey@ --- *                                            \
 106  *                                                                      \
 107  * Arguments:   @pre_cfbctx *ctx@ = pointer to CFB context block        \
 108  *              @const pre_ctx *k@ = pointer to cipher context          \
 109  *                                                                      \
 110  * Returns:     ---                                                     \
 111  *                                                                      \
 112  * Use:         Sets the CFB context to use a different cipher key.     \
 113  */                                                                     \
 114                                                                         \
 115 extern void pre##_cfbsetkey(pre##_cfbctx */*ctx*/,                      \
 116                             const pre##_ctx */*k*/);                    \
 117                                                                         \
 118 /* --- @pre_cfbinit@ --- *                                              \
 119  *                                                                      \
 120  * Arguments:   @pre_cfbctx *ctx@ = pointer to cipher context           \
 121  *              @const void *key@ = pointer to the key buffer           \
 122  *              @size_t sz@ = size of the key                           \
 123  *              @const void *iv@ = pointer to initialization vector     \
 124  *                                                                      \
 125  * Returns:     ---                                                     \
 126  *                                                                      \
 127  * Use:         Initializes a CFB context ready for use.  You should    \
 128  *              ensure that the IV chosen is unique: reusing an IV will \
 129  *              compromise the security of at least the first block     \
 130  *              encrypted.  This is equivalent to calls to @pre_init@,  \
 131  *              @pre_cfbsetkey@ and @pre_cfbsetiv@.                     \
 132  */                                                                     \
 133                                                                         \
 134 extern void pre##_cfbinit(pre##_cfbctx */*ctx*/,                        \
 135                           const void */*key*/, size_t /*sz*/,           \
 136                           const void */*iv*/);                          \
 137                                                                         \
 138 /* --- @pre_cfbencrypt@ --- *                                           \
 139  *                                                                      \
 140  * Arguments:   @pre_cfbctx *ctx@ = pointer to CFB context block        \
 141  *              @const void *src@ = pointer to source data              \
 142  *              @void *dest@ = pointer to destination data              \
 143  *              @size_t sz@ = size of block to be encrypted             \
 144  *                                                                      \
 145  * Returns:     ---                                                     \
 146  *                                                                      \
 147  * Use:         Encrypts a block with a block cipher in CFB mode.  The  \
 148  *              input block may be arbitrary in size.  CFB mode is not  \
 149  *              sensitive to block boundaries.                          \
 150  */                                                                     \
 151                                                                         \
 152 extern void pre##_cfbencrypt(pre##_cfbctx */*ctx*/,                     \
 153                              const void */*src*/, void */*dest*/,       \
 154                              size_t /*sz*/);                            \
 155                                                                         \
 156 /* --- @pre_cfbencrypt@ --- *                                           \
 157  *                                                                      \
 158  * Arguments:   @pre_cfbctx *ctx@ = pointer to CFB context block        \
 159  *              @const void *src@ = pointer to source data              \
 160  *              @void *dest@ = pointer to destination data              \
 161  *              @size_t sz@ = size of block to be encrypted             \
 162  *                                                                      \
 163  * Returns:     ---                                                     \
 164  *                                                                      \
 165  * Use:         Decrypts a block with a block cipher in CFB mode.  The  \
 166  *              input block may be arbitrary in size.  CFB mode is not  \
 167  *              sensitive to block boundaries.                          \
 168  */                                                                     \
 169                                                                         \
 170 extern void pre##_cfbdecrypt(pre##_cfbctx */*ctx*/,                     \
 171                              const void */*src*/, void */*dest*/,       \
 172                              size_t /*sz*/);                            \
 173                                                                         \
 174 /* --- Generic cipher interface --- */                                  \
 175                                                                         \
 176 extern const gccipher pre##_cfb;
 177
 178 /*----- That's all, folks -------------------------------------------------*/
 179
 180 #ifdef __cplusplus
 181   }
 182 #endif
 183
 184 #endif