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1 | /* -*-c-*- |
2 | * |
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3 | * Generalized version of DSA |
4 | * |
5 | * (c) 2004 Straylight/Edgeware |
6 | */ |
7 | |
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8 | /*----- Licensing notice --------------------------------------------------* |
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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. |
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16 | * |
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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. |
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21 | * |
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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 | |
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28 | /*----- Header files ------------------------------------------------------*/ |
29 | |
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30 | #include "dsa.h" |
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31 | #include "gdsa.h" |
32 | #include "group.h" |
33 | #include "ghash.h" |
34 | #include "mpbarrett.h" |
35 | #include "mprand.h" |
36 | |
37 | /*----- Main code ---------------------------------------------------------*/ |
38 | |
39 | /* --- @gdsa_beginhash@ --- * |
40 | * |
41 | * Arguments: @const gdsa *c@ = pointer to the context structure |
42 | * |
43 | * Returns: A hashing context for you to hash the message. |
44 | * |
45 | * Use: Initializes a hash function correctly for you to hash a |
46 | * message. Requires @h@. |
47 | */ |
48 | |
49 | ghash *gdsa_beginhash(const gdsa *c) { return (GH_INIT(c->h)); } |
50 | |
51 | /* --- @gdsa_endhash@ --- * |
52 | * |
53 | * Arguments: @const gdsa *c@ = pointer to the context structure |
54 | * @ghash *h@ = the hashing context |
55 | * |
56 | * Returns: --- |
57 | * |
58 | * Use: Does any final thing that DSA wants to do when hashing a |
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59 | * message. (Actually, there's nothing.) The hashing context |
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60 | * isn't finalized. |
61 | */ |
62 | |
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63 | void gdsa_endhash(const gdsa *c, ghash *h) { ; } |
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64 | |
65 | /* --- @gdsa_sign@ --- * |
66 | * |
67 | * Arguments: @const gdsa *c@ = my context structure |
68 | * @gdsa_sig *s@ = where to put the signature (initialized) |
69 | * @const void *m@ = pointer to message hash |
70 | * @mp *k@ = random exponent for this message or null |
71 | * |
72 | * Returns: --- |
73 | * |
74 | * Use: Signs a message. Requires @g@, @u@, @h@, and @r@ if @k@ is |
75 | * null. This is a better idea than inventing @k@ yourself. |
76 | */ |
77 | |
78 | void gdsa_sign(const gdsa *c, gdsa_sig *s, const void *m, mp *k) |
79 | { |
80 | group *g = c->g; |
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81 | mp *mr = dsa_h2n(MP_NEW, g->r, m, c->h->hashsz); |
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82 | ge *z = G_CREATE(g); |
83 | mp *sr = s->r, *ss = s->s; |
84 | mpbarrett b; |
85 | |
86 | if (k) { MP_COPY(k); goto have_k; } |
87 | new_k: |
88 | k = mprand_range(k, g->r, c->r, 0); |
89 | have_k: |
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90 | if (MP_ZEROP(k)) goto new_k; |
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91 | G_EXP(g, z, g->g, k); |
92 | sr = G_TOINT(g, sr, z); assert(sr); |
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93 | if (MP_ZEROP(sr)) goto new_k; |
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94 | |
95 | mp_div(0, &sr, sr, g->r); |
96 | mpbarrett_create(&b, g->r); |
97 | ss = mp_mul(ss, sr, c->u); ss = mpbarrett_reduce(&b, ss, ss); |
98 | ss = mp_add(ss, ss, mr); mp_div(0, &ss, ss, g->r); |
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99 | k = mp_modinv(k, k, g->r); |
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100 | ss = mp_mul(ss, ss, k); ss = mpbarrett_reduce(&b, ss, ss); |
101 | s->r = sr; s->s = ss; |
102 | mp_drop(k); mp_drop(mr); mpbarrett_destroy(&b); G_DESTROY(g, z); |
103 | } |
104 | |
105 | /* --- @gdsa_verify@ --- * |
106 | * |
107 | * Arguments: @const gdsa *c@ = my context structure |
108 | * @const gdsa_sig *s@ = the signature to verify |
109 | * @const void *m@ = pointer to message hash |
110 | * |
111 | * Returns: Zero if OK, negative on failure. |
112 | * |
113 | * Use: Checks a signature on a message, Requires @g@, @p@ and @h@. |
114 | */ |
115 | |
116 | int gdsa_verify(const gdsa *c, const gdsa_sig *s, const void *m) |
117 | { |
118 | group *g = c->g; |
119 | group_expfactor e[2]; |
120 | mpbarrett b; |
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121 | mp *h, *t; |
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122 | ge *w; |
123 | int rc = -1; |
124 | |
125 | if (MP_CMP(s->r, <, MP_ONE) || MP_CMP(s->r, >=, g->r) || |
126 | MP_CMP(s->s, <, MP_ONE) || MP_CMP(s->s, >=, g->r)) |
127 | return (-1); |
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128 | mpbarrett_create(&b, g->r); h = mp_modinv(MP_NEW, s->s, g->r); |
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129 | e[0].base = g->g; e[1].base = c->p; |
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130 | t = dsa_h2n(MP_NEW, g->r, m, c->h->hashsz); mp_div(0, &t, t, g->r); |
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131 | t = mp_mul(t, t, h); e[0].exp = t = mpbarrett_reduce(&b, t, t); |
132 | h = mp_mul(h, s->r, h); e[1].exp = h = mpbarrett_reduce(&b, h, h); |
133 | w = G_CREATE(g); G_MEXP(g, w, e, 2); |
134 | t = G_TOINT(g, t, w); if (!t) goto done; |
135 | mp_div(0, &t, t, g->r); if (MP_EQ(t, s->r)) rc = 0; |
136 | done: |
137 | G_DESTROY(g, w); mp_drop(t); mp_drop(h); mpbarrett_destroy(&b); |
138 | return (rc); |
139 | } |
140 | |
141 | /*----- Test rig ----------------------------------------------------------*/ |
142 | |
143 | #ifdef TEST_RIG |
144 | |
145 | static group *getgroup(const char *p) { |
146 | group *g; qd_parse qd; |
147 | qd.p = p; qd.e = 0; g = group_parse(&qd); |
148 | if (g && !qd_eofp(&qd)) { G_DESTROYGROUP(g); g = 0; qd.e = "junk at eof"; } |
149 | if (!g) { fprintf(stderr, "bad group string `%.*s|%s': %s\n", qd.p - p, |
150 | p, qd.p, qd.e); exit(1); } |
151 | return (g); |
152 | } |
153 | |
154 | static ge *getge(group *g, const char *p) { |
155 | ge *x = G_CREATE(g); |
156 | if (group_readstring(g, x, p, 0)) { |
157 | fprintf(stderr, "bad group element `%s'\n", p); |
158 | exit(1); |
159 | } |
160 | return (x); |
161 | } |
162 | |
163 | static void showge(group *g, const char *p, ge *x) { |
164 | fprintf(stderr, "*** %s = ", p); group_writefile(g, x, stderr); |
165 | putc('\n', stderr); |
166 | } |
167 | |
168 | static void showmp(const char *p, mp *x, int r) { |
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169 | fprintf(stderr, "*** %s = ", p); mp_writefile(x, stderr, r); |
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170 | putc('\n', stderr); |
171 | } |
172 | |
173 | static int tsign(dstr *v) |
174 | { |
175 | gdsa c; |
176 | gdsa_sig s, ss = GDSA_SIG_INIT; |
177 | ghash *h; |
178 | mp *k; |
179 | int ok = 1; |
180 | |
181 | c.g = getgroup(v[0].buf); c.h = ghash_byname(v[1].buf); |
182 | c.u = *(mp **)v[2].buf; k = *(mp **)v[4].buf; |
183 | s.r = *(mp **)v[5].buf; s.s = *(mp **)v[6].buf; |
184 | |
185 | h = gdsa_beginhash(&c); |
186 | GH_HASH(h, v[3].buf, v[3].len); |
187 | gdsa_endhash(&c, h); |
188 | gdsa_sign(&c, &ss, GH_DONE(h, 0), k); |
189 | if (!MP_EQ(s.r, ss.r) || !MP_EQ(s.s, ss.s)) { |
190 | ok = 0; |
191 | fprintf(stderr, "*** sign failed!\n"); |
192 | fprintf(stderr, "*** group: %s\n", v[0].buf); |
193 | fprintf(stderr, "*** hash: %s\n", c.h->name); |
194 | showmp("private key", c.u, 16); |
195 | fprintf(stderr, "*** message: `%s'\n", v[3].buf); |
196 | showmp("computed r", ss.r, 16); showmp("computed s", ss.s, 16); |
197 | showmp("expected r", s.r, 16); showmp("expected s", s.s, 16); |
198 | } |
199 | mp_drop(s.r); mp_drop(s.s); mp_drop(ss.r); mp_drop(ss.s); |
200 | mp_drop(k); mp_drop(c.u); G_DESTROYGROUP(c.g); GH_DESTROY(h); |
201 | assert(mparena_count(MPARENA_GLOBAL) == 0); |
202 | return (ok); |
203 | } |
204 | |
205 | static int tverify(dstr *v) |
206 | { |
207 | gdsa c; |
208 | gdsa_sig s; |
209 | ghash *h; |
210 | int rc, erc; |
211 | int ok = 1; |
212 | |
213 | c.g = getgroup(v[0].buf); c.h = ghash_byname(v[1].buf); |
214 | c.p = getge(c.g, v[2].buf); |
215 | s.r = *(mp **)v[4].buf; s.s = *(mp **)v[5].buf; |
216 | erc = *(int *)v[6].buf; |
217 | |
218 | h = gdsa_beginhash(&c); |
219 | GH_HASH(h, v[3].buf, v[3].len); |
220 | gdsa_endhash(&c, h); |
221 | rc = gdsa_verify(&c, &s, GH_DONE(h, 0)); |
222 | if (!rc != !erc) { |
223 | ok = 0; |
224 | fprintf(stderr, "*** verify failed!\n"); |
225 | fprintf(stderr, "*** group: %s\n", v[0].buf); |
226 | fprintf(stderr, "*** hash: %s\n", c.h->name); |
227 | showge(c.g, "public key", c.p); |
228 | fprintf(stderr, "*** message: `%s'\n", v[3].buf); |
229 | showmp("sig r", s.r, 16); showmp("sig s", s.s, 16); |
230 | fprintf(stderr, "*** expected %s\n", !erc ? "pass" : "fail"); |
231 | } |
232 | mp_drop(s.r); mp_drop(s.s); G_DESTROY(c.g, c.p); G_DESTROYGROUP(c.g); |
233 | GH_DESTROY(h); |
234 | assert(mparena_count(MPARENA_GLOBAL) == 0); |
235 | return (ok); |
236 | } |
237 | |
238 | static const test_chunk tests[] = { |
239 | { "sign", tsign, { &type_string, &type_string, &type_mp, &type_string, |
240 | &type_mp, &type_mp, &type_mp } }, |
241 | { "verify", tverify, { &type_string, &type_string, &type_string, |
242 | &type_string, &type_mp, &type_mp, &type_int } }, |
243 | { 0 } |
244 | }; |
245 | |
246 | int main(int argc, char *argv[]) |
247 | { |
248 | sub_init(); |
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249 | test_run(argc, argv, tests, SRCDIR "/t/gdsa"); |
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250 | return (0); |
251 | } |
252 | |
253 | #endif |
254 | |
255 | /*----- That's all, folks -------------------------------------------------*/ |