3 * Optimal asymmetric encryption packing
5 * (c) 2000 Straylight/Edgeware
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of Catacomb.
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.
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.
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,
28 /*----- Header files ------------------------------------------------------*/
32 #include <mLib/alloc.h>
33 #include <mLib/bits.h>
34 #include <mLib/dstr.h>
42 /*----- Main code ---------------------------------------------------------*/
44 /* --- @oaep_encode@ --- *
46 * Arguments: @mp *d@ = where to put the answer
47 * @const void *m@ = pointer to message data
48 * @size_t msz@ = size of message data
49 * @octet *b@ = spare buffer
50 * @size_t sz@ = size of the buffer (big enough)
51 * @unsigned long nbits@ = length of bits of @n@
52 * @void *p@ = pointer to OAEP parameter block
54 * Returns: The encoded plaintext, or null on failure.
56 * Use: Implements the operation @EME-OAEP-ENCODE@, as defined in
57 * PKCS#1 v. 2.0 (RFC2437).
60 mp
*oaep_encode(mp
*d
, const void *m
, size_t msz
, octet
*b
, size_t sz
,
61 unsigned long nbits
, void *p
)
64 size_t hsz
= o
->ch
->hashsz
;
71 /* --- Ensure that everything is sensibly sized --- */
73 if (2 * hsz
+ 2 + msz
> sz
)
76 /* --- Make the `seed' value --- */
81 GR_FILL(o
->r
, q
, hsz
);
83 /* --- Fill in the rest of the buffer --- */
86 GH_HASH(h
, o
->ep
, o
->epsz
);
90 n
= sz
- 2 * hsz
- msz
- 1;
96 /* --- Do the packing --- */
99 c
= GC_INIT(o
->cc
, q
, hsz
);
100 GC_ENCRYPT(c
, mq
, mq
, n
);
103 c
= GC_INIT(o
->cc
, mq
, n
);
104 GC_ENCRYPT(c
, q
, q
, hsz
);
109 return (mp_loadb(d
, b
, sz
+ 1));
112 /* --- @oaep_decode@ --- *
114 * Arguments: @mp *m@ = the decrypted message
115 * @octet *b@ = pointer to a buffer to work in
116 * @size_t sz@ = the size of the buffer (big enough)
117 * @unsigned long nbits@ = the number of bits in @n@
118 * @void *p@ = pointer to OAEP parameter block
120 * Returns: The length of the output string if successful, negative on
123 * Use: Implements the operation @EME-OAEP-DECODE@, as defined in
124 * PKCS#1 v. 2.0 (RFC2437).
127 int oaep_decode(mp
*m
, octet
*b
, size_t sz
, unsigned long nbits
, void *p
)
136 size_t hsz
= o
->ch
->hashsz
;
138 /* --- Ensure that the block is large enough --- */
140 if (sz
< 2 * hsz
) /* Doesn't depend on ciphertext */
143 /* --- Decrypt the message --- */
147 goodp
&= ct_inteq(*q
, 0);
152 c
= GC_INIT(o
->cc
, mq
, n
);
153 GC_DECRYPT(c
, q
, q
, hsz
);
156 c
= GC_INIT(o
->cc
, q
, hsz
);
157 GC_DECRYPT(c
, mq
, mq
, n
);
161 /* --- Check the hash on the encoding parameters --- */
164 GH_HASH(h
, o
->ep
, o
->epsz
);
167 goodp
&= ct_memeq(q
, mq
, hsz
);
169 /* --- Now find the start of the actual message --- */
172 while (*pp
== 0 && pp
< qq
)
174 goodp
&= ~ct_intle(qq
- b
, pp
- b
);
175 goodp
&= ct_inteq(*pp
, 1);
179 return (goodp ? n
: -1);
182 /*----- That's all, folks -------------------------------------------------*/