3 * [RSA encryption with padding *
4 * (c) 2000 Straylight/Edgeware
7 /*----- Licensing notice --------------------------------------------------*
9 * This file is part of Catacomb.
11 * Catacomb is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU Library General Public License as
13 * published by the Free Software Foundation; either version 2 of the
14 * License, or (at your option) any later version.
16 * Catacomb is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU Library General Public License for more details.
21 * You should have received a copy of the GNU Library General Public
22 * License along with Catacomb; if not, write to the Free
23 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
27 /*----- Header files ------------------------------------------------------*/
29 #include <mLib/alloc.h>
30 #include <mLib/bits.h>
31 #include <mLib/dstr.h>
32 #include <mLib/macros.h>
38 /*----- Public key operations ---------------------------------------------*/
40 /* --- @rsa_pubcreate@ --- *
42 * Arguments: @rsa_pubctx *rd@ = pointer to an RSA public key context
43 * @rsa_pub *rp@ = pointer to RSA public key
47 * Use: Initializes an RSA public-key context.
50 void rsa_pubcreate(rsa_pubctx *rd, rsa_pub *rp)
52 rd->rp = rp; mp_shrink(rp->e);
53 mpmont_create(&rd->mm, rp->n);
56 /* --- @rsa_pubdestroy@ --- *
58 * Arguments: @rsa_pubctx *rd@ = pointer to an RSA public key context
62 * Use: Destroys an RSA public-key context.
65 void rsa_pubdestroy(rsa_pubctx *rd)
67 mpmont_destroy(&rd->mm);
70 /* --- @rsa_pubop@ --- *
72 * Arguments: @rsa_pubctx *rd@ = pointer to an RSA public key context
73 * @mp *d@ = destination
74 * @mp *p@ = input message
76 * Returns: The transformed output message.
78 * Use: Performs an RSA public key operation.
81 mp *rsa_pubop(rsa_pubctx *rd, mp *d, mp *p)
86 if (MP_EQ(e, MP_THREE)) {
88 d = mpmont_mul(&rd->mm, d, p, rd->mm.r2);
89 d = mp_sqr(d, d); d = mpmont_reduce(&rd->mm, d, d);
90 d = mpmont_mul(&rd->mm, d, d, p);
95 if (MP_LEN(e) == 1 && e->v[0] == 65537)
97 if (0 && MP_LEN(e) == 2 && e->v[0] == 1 && e->v[1] == (1 << (16 - MPW_BITS)))
101 d = mpmont_mul(&rd->mm, d, p, rd->mm.r2);
102 for (i = 0; i < 16; i++)
103 { d = mp_sqr(d, d); d = mpmont_reduce(&rd->mm, d, d); }
104 d = mpmont_mul(&rd->mm, d, d, p);
108 return (mpmont_exp(&rd->mm, d, p, rd->rp->e));
111 /* --- @rsa_qpubop@ --- *
113 * Arguments: @rsa_pub *rp@ = pointer to RSA parameters
114 * @mp *d@ = destination
115 * @mp *p@ = input message
117 * Returns: Correctly transformed output message.
119 * Use: Performs an RSA public key operation.
122 mp *rsa_qpubop(rsa_pub *rp, mp *d, mp *c)
125 rsa_pubcreate(&rd, rp);
126 d = rsa_pubop(&rd, d, c);
131 /*----- Operations with padding -------------------------------------------*/
133 /* --- @rsa_encrypt@ --- *
135 * Arguments: @rsa_pubctx *rp@ = pointer to an RSA public key context
136 * @mp *d@ = proposed destination integer
137 * @const void *m@ = pointer to input message
138 * @size_t msz@ = size of input message
139 * @rsa_pad *e@ = encoding procedure
140 * @void *earg@ = argument pointer for encoding procedure
142 * Returns: The encrypted message, as a multiprecision integer, or null
145 * Use: Does RSA encryption.
148 mp *rsa_encrypt(rsa_pubctx *rp, mp *d, const void *m, size_t msz,
149 rsa_pad *e, void *earg)
152 unsigned long nb = mp_bits(rp->rp->n);
153 size_t n = (nb + 7)/8;
154 arena *a = d && d->a ? d->a->a : arena_global;
157 d = e(d, m, msz, p, n, nb, earg);
159 return (d ? rsa_pubop(rp, d, d) : 0);
162 /* --- @rsa_verify@ --- *
164 * Arguments: @rsa_pubctx *rp@ = pointer to an RSA public key contxt
165 * @mp *s@ = the signature, as a multiprecision integer
166 * @const void *m@ = pointer to message to verify, or null
167 * @size_t msz@ = size of input message
168 * @dstr *d@ = pointer to output string, or null
169 * @rsa_vfrunpad *e@ = decoding procedure
170 * @void *earg@ = argument pointer for decoding procedure
172 * Returns: The length of the output string if successful (0 if no output
173 * was wanted); negative on failure.
175 * Use: Does RSA signature verification. To use a signature scheme
176 * with recovery, pass in @m == 0@ and @d != 0@: the recovered
177 * message should appear in @d@. To use a signature scheme with
178 * appendix, provide @m != 0@ and @d == 0@; the result should be
182 int rsa_verify(rsa_pubctx *rp, mp *s, const void *m, size_t msz,
183 dstr *d, rsa_vrfunpad *e, void *earg)
185 mp *p = rsa_pubop(rp, MP_NEW, s);
186 unsigned long nb = mp_bits(rp->rp->n);
187 size_t n = (nb + 7)/8;
191 /* --- Decoder protocol --- *
193 * We deal with two kinds of decoders: ones with message recovery and ones
194 * with appendix. A decoder with recovery will leave a message in the
195 * buffer and exit nonzero: we'll check that against @m@ if provided and
196 * just leave it otherwise. A decoder with appendix will inspect @m@ and
197 * return zero or @-1@ itself.
202 rc = e(p, m, msz, (octet *)d->buf + d->len, n, nb, earg);
204 if (rc != msz || MEMCMP(d->buf + d->len, !=, m, msz))
216 /*----- That's all, folks -------------------------------------------------*/