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

   1 /* -*-c-*-
   2  *
   3  * $Id: cfb.h,v 1.5 2004/04/08 01:36:15 mdw Exp $
   4  *
   5  * Ciphertext 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_CFB_H
  31 #define CATACOMB_CFB_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 /*----- Data structures ---------------------------------------------------*/
  48
  49 /* --- @CFB_DECL@ --- *
  50  *
  51  * Arguments:   @PRE@, @pre@ = prefixes for the underlying block cipher
  52  *
  53  * Use:         Creates declarations for CFB mode.
  54  */
  55
  56 #define CFB_DECL(PRE, pre)                                              \
  57                                                                         \
  58 /* --- Ciphertext feedback context --- */                               \
  59                                                                         \
  60 typedef struct pre##_cfbctx {                                           \
  61   pre##_ctx ctx;                        /* Underlying cipher context */ \
  62   unsigned off;                         /* Offset into @iv@ buffer */   \
  63   octet iv[PRE##_BLKSZ];                /* Previous ciphertext or IV */ \
  64 } pre##_cfbctx;                                                         \
  65                                                                         \
  66 /* --- @pre_cfbgetiv@ --- *                                             \
  67  *                                                                      \
  68  * Arguments:   @const pre_cfbctx *ctx@ = pointer to CFB context block  \
  69  *              @void *iv@ = pointer to output data block               \
  70  *                                                                      \
  71  * Returns:     ---                                                     \
  72  *                                                                      \
  73  * Use:         Reads the currently set IV.  Reading and setting an IV  \
  74  *              is not transparent to the cipher.  It will add a `step' \
  75  *              which must be matched by a similar operation during     \
  76  *              decryption.                                             \
  77  */                                                                     \
  78                                                                         \
  79 extern void pre##_cfbgetiv(const pre##_cfbctx */*ctx*/,                 \
  80                            void */*iv*/);                               \
  81                                                                         \
  82 /* --- @pre_cfbsetiv@ --- *                                             \
  83  *                                                                      \
  84  * Arguments:   @pre_cfbctx *ctx@ = pointer to CFB context block        \
  85  *              @cnost void *iv@ = pointer to IV to set                 \
  86  *                                                                      \
  87  * Returns:     ---                                                     \
  88  *                                                                      \
  89  * Use:         Sets the IV to use for subsequent encryption.           \
  90  */                                                                     \
  91                                                                         \
  92 extern void pre##_cfbsetiv(pre##_cfbctx */*ctx*/,                       \
  93                            const void */*iv*/);                         \
  94                                                                         \
  95 /* --- @pre_cfbbdry@ --- *                                              \
  96  *                                                                      \
  97  * Arguments:   @pre_cfbctx *ctx@ = pointer to CFB context block        \
  98  *                                                                      \
  99  * Returns:     ---                                                     \
 100  *                                                                      \
 101  * Use:         Inserts a boundary during encryption.  Successful       \
 102  *              decryption must place a similar boundary.               \
 103  */                                                                     \
 104                                                                         \
 105 extern void pre##_cfbbdry(pre##_cfbctx */*ctx*/);                       \
 106                                                                         \
 107 /* --- @pre_cfbsetkey@ --- *                                            \
 108  *                                                                      \
 109  * Arguments:   @pre_cfbctx *ctx@ = pointer to CFB context block        \
 110  *              @const pre_ctx *k@ = pointer to cipher context          \
 111  *                                                                      \
 112  * Returns:     ---                                                     \
 113  *                                                                      \
 114  * Use:         Sets the CFB context to use a different cipher key.     \
 115  */                                                                     \
 116                                                                         \
 117 extern void pre##_cfbsetkey(pre##_cfbctx */*ctx*/,                      \
 118                             const pre##_ctx */*k*/);                    \
 119                                                                         \
 120 /* --- @pre_cfbinit@ --- *                                              \
 121  *                                                                      \
 122  * Arguments:   @pre_cfbctx *ctx@ = pointer to cipher context           \
 123  *              @const void *key@ = pointer to the key buffer           \
 124  *              @size_t sz@ = size of the key                           \
 125  *              @const void *iv@ = pointer to initialization vector     \
 126  *                                                                      \
 127  * Returns:     ---                                                     \
 128  *                                                                      \
 129  * Use:         Initializes a CFB context ready for use.  You should    \
 130  *              ensure that the IV chosen is unique: reusing an IV will \
 131  *              compromise the security of at least the first block     \
 132  *              encrypted.  This is equivalent to calls to @pre_init@,  \
 133  *              @pre_cfbsetkey@ and @pre_cfbsetiv@.                     \
 134  */                                                                     \
 135                                                                         \
 136 extern void pre##_cfbinit(pre##_cfbctx */*ctx*/,                        \
 137                           const void */*key*/, size_t /*sz*/,           \
 138                           const void */*iv*/);                          \
 139                                                                         \
 140 /* --- @pre_cfbencrypt@ --- *                                           \
 141  *                                                                      \
 142  * Arguments:   @pre_cfbctx *ctx@ = pointer to CFB context block        \
 143  *              @const void *src@ = pointer to source data              \
 144  *              @void *dest@ = pointer to destination data              \
 145  *              @size_t sz@ = size of block to be encrypted             \
 146  *                                                                      \
 147  * Returns:     ---                                                     \
 148  *                                                                      \
 149  * Use:         Encrypts a block with a block cipher in CFB mode.  The  \
 150  *              input block may be arbitrary in size.  CFB mode is not  \
 151  *              sensitive to block boundaries.                          \
 152  */                                                                     \
 153                                                                         \
 154 extern void pre##_cfbencrypt(pre##_cfbctx */*ctx*/,                     \
 155                              const void */*src*/, void */*dest*/,       \
 156                              size_t /*sz*/);                            \
 157                                                                         \
 158 /* --- @pre_cfbencrypt@ --- *                                           \
 159  *                                                                      \
 160  * Arguments:   @pre_cfbctx *ctx@ = pointer to CFB 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:         Decrypts a block with a block cipher in CFB mode.  The  \
 168  *              input block may be arbitrary in size.  CFB mode is not  \
 169  *              sensitive to block boundaries.                          \
 170  */                                                                     \
 171                                                                         \
 172 extern void pre##_cfbdecrypt(pre##_cfbctx */*ctx*/,                     \
 173                              const void */*src*/, void */*dest*/,       \
 174                              size_t /*sz*/);                            \
 175                                                                         \
 176 /* --- Generic cipher interface --- */                                  \
 177                                                                         \
 178 extern const gccipher pre##_cfb;
 179
 180 /*----- That's all, folks -------------------------------------------------*/
 181
 182 #ifdef __cplusplus
 183   }
 184 #endif
 185
 186 #endif