3 * Probabistic signature scheme
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>
35 #include <mLib/macros.h>
42 /*----- Magic statics -----------------------------------------------------*/
44 static const octet z8
[8] = { 0 };
46 /*----- Main code ---------------------------------------------------------*/
48 /* --- @pss_encode@ --- *
50 * Arguments: @mp *d@ = where to put the answer
51 * @const void *m@ = pointer to the message hash
52 * @size_t msz@ = the size of the message hash
53 * @octet *b@ = scratch buffer
54 * @size_t sz@ = sizeo of the buffer (large enough)
55 * @unsigned long nbits@ = size in bits of @n@
56 * @void *p@ = pointer to the PSS parameters
58 * Returns: Encoded message representative, or null on error.
60 * Use: Implements the operation @EMSA-PSS-ENCODE@, as defined in
61 * PKCS#1 v. 2.1 (RFC3447).
64 mp
*pss_encode(mp
*d
, const void *m
, size_t msz
, octet
*b
, size_t sz
,
65 unsigned long nbits
, void *p
)
72 size_t pssz
, hsz
= pp
->ch
->hashsz
;
74 /* --- Check the message length --- */
78 mask
= (1 << nbits
%8) - 1;
79 if (!mask
) mask
= 0xff;
80 if (hsz
+ pp
->ssz
+ 2 > sz
)
83 /* --- Generate a random salt --- */
85 pssz
= sz
- pp
->ssz
- hsz
- 2;
90 GR_FILL(pp
->r
, s
, pp
->ssz
);
92 /* --- Compute the salted hash --- */
97 GH_HASH(h
, s
, pp
->ssz
);
101 /* --- Do the masking --- */
103 c
= GC_INIT(pp
->cc
, r
, hsz
);
104 GC_ENCRYPT(c
, b
, b
, pssz
+ pp
->ssz
+ 1);
107 return (mp_loadb(d
, b
, sz
));
110 /* --- @pss_decode@ --- *
112 * Arguments: @mp *s@ = the message representative
113 * @const void *m@ = the original message
114 * @size_t msz@ = the message size
115 * @octet *b@ = a scratch buffer
116 * @size_t sz@ = size of the buffer (large enough)
117 * @unsigned long nbits@ = number of bits in @n@
118 * @void *p@ = pointer to PKCS1 parameters
120 * Returns: The length of the output string if successful, negative on
123 * Use: Implements the operation @EMSA_PSS_VERIFY@, as defined in
124 * PCSK#1 v. 2.1 (RFC3447).
127 int pss_decode(mp
*mi
, const void *m
, size_t msz
, octet
*b
, size_t sz
,
128 unsigned long nbits
, void *p
)
135 size_t pssz
, hsz
= pp
->ch
->hashsz
, i
;
138 /* --- Check the message length --- */
142 if (mp_octets(mi
) > sz
)
144 mask
= (1 << nbits
%8) - 1;
145 if (!mask
) mask
= 0xff;
146 if (hsz
+ pp
->ssz
+ 2 > sz
)
148 mp_storeb(mi
, b
, sz
);
150 /* --- Split up the buffer --- */
152 pssz
= sz
- hsz
- pp
->ssz
- 2;
158 /* --- Decode the seed --- */
162 c
= GC_INIT(pp
->cc
, r
, hsz
);
163 GC_DECRYPT(c
, b
, b
, pssz
+ pp
->ssz
+ 1);
166 for (i
= 0; i
< pssz
; i
++)
167 if (b
[i
]) return (-1);
171 /* --- Hash the message --- */
176 GH_HASH(h
, s
, pp
->ssz
);
178 rc
= MEMCMP(s
, ==, r
, hsz
);
180 if (!rc
) return (-1);
187 /*----- That's all, folks -------------------------------------------------*/