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1 | /* -*-c-*- |
2 | * |
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3 | * $Id$ |
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4 | * |
5 | * Generalized version of KCDSA |
6 | * |
7 | * (c) 2004 Straylight/Edgeware |
8 | */ |
9 | |
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10 | /*----- Licensing notice --------------------------------------------------* |
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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. |
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18 | * |
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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. |
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23 | * |
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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 | |
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30 | /*----- Header files ------------------------------------------------------*/ |
31 | |
32 | #include "gkcdsa.h" |
33 | #include "group.h" |
34 | #include "ghash.h" |
35 | #include "mpbarrett.h" |
36 | #include "mprand.h" |
37 | |
38 | /*----- Main code ---------------------------------------------------------*/ |
39 | |
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40 | /* --- @gkcdsa_beginhash@ --- * |
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41 | * |
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42 | * Arguments: @const gkcdsa *c@ = pointer to the context structure |
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43 | * |
44 | * Returns: A hashing context for you to hash the message. |
45 | * |
46 | * Use: Initializes a hash function correctly for you to hash a |
47 | * message. Requires @h@, @g@ and @p@. |
48 | */ |
49 | |
50 | ghash *gkcdsa_beginhash(const gkcdsa *c) |
51 | { |
52 | ghash *h = GH_INIT(c->h); |
53 | mp *v = G_TOINT(c->g, MP_NEW, c->p); |
54 | size_t sz = c->h->bufsz; |
55 | void *p = xmalloc(sz); |
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56 | if (/*ouch*/ !v) memset(p, 0, sz); |
57 | else mp_storeb(v, p, sz); |
58 | GH_HASH(h, p, sz); |
59 | mp_drop(v); xfree(p); |
60 | return (h); |
61 | } |
62 | |
63 | /* --- @gkcdsa_endhash@ --- * |
64 | * |
65 | * Arguments: @const gkcdsa *c@ = pointer to the context structure |
66 | * @ghash *h@ = the hashing context |
67 | * |
68 | * Returns: --- |
69 | * |
70 | * Use: Does any final thing that KCDSA wants to do when hashing a |
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71 | * message. (Actually, there's nothing.) The hashing context |
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72 | * isn't finalized. |
73 | */ |
74 | |
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75 | void gkcdsa_endhash(const gkcdsa *c, ghash *h) { ; } |
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76 | |
77 | /* --- @hashge@ --- * |
78 | * |
79 | * Arguments: @group *g@ = abstract group |
80 | * @const gchash *hc@ = hash class |
81 | * @ge *w@ = a group element |
82 | * |
83 | * Returns: A hash context, with the hash of @w@ in it. |
84 | */ |
85 | |
86 | static ghash *hashge(group *g, const gchash *hc, ge *w) |
87 | { |
88 | ghash *h; |
89 | size_t sz; |
90 | void *p; |
91 | buf b; |
92 | int rc; |
93 | |
94 | sz = hc->hashsz; |
95 | if (sz < g->noctets) |
96 | sz = g->noctets; |
97 | p = xmalloc(sz); |
98 | buf_init(&b, p, sz); |
99 | rc = G_TORAW(g, &b, w); |
100 | assert(rc == 0); |
101 | h = GH_INIT(hc); |
102 | GH_HASH(h, BBASE(&b), BLEN(&b)); |
103 | xfree(p); |
104 | return (h); |
105 | } |
106 | |
107 | /* --- @gkcdsa_sign@ --- * |
108 | * |
109 | * Arguments: @const gkcdsa *c@ = my context structure |
110 | * @gkcdsa_sig *s@ = where to put the signature (initialized) |
111 | * @const void *m@ = pointer to message hash |
112 | * @mp *k@ = random exponent for this message or null |
113 | * |
114 | * Returns: --- |
115 | * |
116 | * Use: Signs a message. Requires @g@, @u@, @h@, and @r@ if @k@ is |
117 | * null. This is a better idea than inventing @k@ yourself. |
118 | */ |
119 | |
120 | void gkcdsa_sign(const gkcdsa *c, gkcdsa_sig *s, const void *m, mp *k) |
121 | { |
122 | group *g = c->g; |
123 | mp *x, *y; |
124 | ge *z = G_CREATE(g); |
125 | size_t hsz = c->h->hashsz; |
126 | ghash *h; |
127 | |
128 | if (k) { MP_COPY(k); goto have_k; } |
129 | new_k: |
130 | k = mprand_range(k, g->r, c->r, 0); |
131 | have_k: |
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132 | if (MP_ZEROP(k)) goto new_k; |
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133 | G_EXP(g, z, g->g, k); |
134 | if (!s->r) s->r = xmalloc(hsz); |
135 | h = hashge(g, c->h, z); GH_DONE(h, s->r); |
136 | |
137 | x = mp_loadb(s->s, m, hsz); |
138 | y = mp_loadb(MP_NEW, s->r, hsz); |
139 | x = mp_xor(x, x, y); |
140 | mp_div(0, &x, x, g->r); |
141 | x = mp_sub(x, g->r, x); |
142 | x = mp_add(x, x, k); |
143 | if (MP_CMP(x, >=, g->r)) x = mp_sub(x, x, g->r); |
144 | x = mp_mul(x, x, c->u); mp_div(0, &x, x, g->r); |
145 | s->s = x; |
146 | mp_drop(k); mp_drop(y); GH_DESTROY(h); G_DESTROY(g, z); |
147 | } |
148 | |
149 | /* --- @gkcdsa_verify@ --- * |
150 | * |
151 | * Arguments: @const gkcdsa *c@ = my context structure |
152 | * @const gkcdsa_sig *s@ = the signature to verify |
153 | * @const void *m@ = pointer to message hash |
154 | * |
155 | * Returns: Zero if OK, negative on failure. |
156 | * |
157 | * Use: Checks a signature on a message, Requires @g@, @p@, @h@. |
158 | */ |
159 | |
160 | int gkcdsa_verify(const gkcdsa *c, const gkcdsa_sig *s, const void *m) |
161 | { |
162 | group *g = c->g; |
163 | size_t hsz = c->h->hashsz; |
164 | group_expfactor e[2]; |
165 | mp *x, *y; |
166 | ghash *h; |
167 | ge *z; |
168 | octet *p; |
169 | int rc = -1; |
170 | |
171 | if (MP_CMP(s->s, <, MP_ONE) || MP_CMP(s->s, >=, g->r)) |
172 | return (-1); |
173 | x = mp_loadb(MP_NEW, m, hsz); y = mp_loadb(MP_NEW, s->r, hsz); |
174 | x = mp_xor(x, x, y); mp_div(0, &x, x, g->r); |
175 | e[0].base = c->p; e[0].exp = s->s; |
176 | e[1].base = g->g; e[1].exp = x; |
177 | z = G_CREATE(g); G_MEXP(g, z, e, 2); |
178 | h = hashge(g, c->h, z); p = GH_DONE(h, 0); |
179 | if (memcmp(p, s->r, hsz) == 0) rc = 0; |
180 | mp_drop(x); mp_drop(y); G_DESTROY(g, z); GH_DESTROY(h); |
181 | return (rc); |
182 | } |
183 | |
184 | /*----- Test rig ----------------------------------------------------------*/ |
185 | |
186 | #ifdef TEST_RIG |
187 | |
188 | static group *getgroup(const char *p) { |
189 | group *g; qd_parse qd; |
190 | qd.p = p; qd.e = 0; g = group_parse(&qd); |
191 | if (g && !qd_eofp(&qd)) { G_DESTROYGROUP(g); g = 0; qd.e = "junk at eof"; } |
192 | if (!g) { fprintf(stderr, "bad group string `%.*s|%s': %s\n", qd.p - p, |
193 | p, qd.p, qd.e); exit(1); } |
194 | return (g); |
195 | } |
196 | |
197 | static ge *getge(group *g, const char *p) { |
198 | ge *x = G_CREATE(g); |
199 | if (group_readstring(g, x, p, 0)) { |
200 | fprintf(stderr, "bad group element `%s'\n", p); |
201 | exit(1); |
202 | } |
203 | return (x); |
204 | } |
205 | |
206 | static void showge(group *g, const char *p, ge *x) { |
207 | fprintf(stderr, "*** %s = ", p); group_writefile(g, x, stderr); |
208 | putc('\n', stderr); |
209 | } |
210 | |
211 | static void showmp(const char *p, mp *x, int r) { |
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212 | fprintf(stderr, "*** %s = ", p); mp_writefile(x, stderr, r); |
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213 | putc('\n', stderr); |
214 | } |
215 | |
216 | static int tsign(dstr *v) |
217 | { |
218 | gdsa c; |
219 | gkcdsa_sig s, ss = GKCDSA_SIG_INIT; |
220 | ghash *h; |
221 | mp *k; |
222 | dstr d = DSTR_INIT; |
223 | mp *x; |
224 | int ok = 1; |
225 | |
226 | c.g = getgroup(v[0].buf); c.h = ghash_byname(v[1].buf); |
227 | c.u = *(mp **)v[2].buf; k = *(mp **)v[4].buf; |
228 | s.r = (octet *)v[5].buf; s.s = *(mp **)v[6].buf; |
229 | DENSURE(&d, c.h->hashsz); d.len = c.h->hashsz; memset(d.buf, 0, d.len); |
230 | ss.r = (octet *)d.buf; |
231 | |
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232 | x = mp_modinv(MP_NEW, c.u, c.g->r); |
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233 | c.p = G_CREATE(c.g); G_EXP(c.g, c.p, c.g->g, x); |
234 | h = gkcdsa_beginhash(&c); |
235 | GH_HASH(h, v[3].buf, v[3].len); |
236 | gkcdsa_endhash(&c, h); |
237 | gkcdsa_sign(&c, &ss, GH_DONE(h, 0), k); |
238 | if (memcmp(s.r, ss.r, c.h->hashsz) || !MP_EQ(s.s, ss.s)) { |
239 | ok = 0; |
240 | fprintf(stderr, "*** sign failed!\n"); |
241 | fprintf(stderr, "*** group: %s\n", v[0].buf); |
242 | fprintf(stderr, "*** hash: %s\n", c.h->name); |
243 | showmp("private key", c.u, 16); |
244 | showge(c.g, "public key", c.p); |
245 | fprintf(stderr, "*** message: `%s'\n", v[3].buf); |
246 | fprintf(stderr, "*** computed r = "); |
247 | type_hex.dump(&d, stderr); putc('\n', stderr); |
248 | showmp("computed s", ss.s, 16); |
249 | fprintf(stderr, "*** computed r = "); |
250 | type_hex.dump(&v[5], stderr); putc('\n', stderr); |
251 | showmp("expected s", s.s, 16); |
252 | } |
253 | mp_drop(s.s); dstr_destroy(&d); mp_drop(ss.s); mp_drop(x); mp_drop(k); |
254 | mp_drop(c.u); G_DESTROY(c.g, c.p); G_DESTROYGROUP(c.g); GH_DESTROY(h); |
255 | assert(mparena_count(MPARENA_GLOBAL) == 0); |
256 | return (ok); |
257 | } |
258 | |
259 | static int tverify(dstr *v) |
260 | { |
261 | gkcdsa c; |
262 | gkcdsa_sig s; |
263 | ghash *h; |
264 | int rc, erc; |
265 | int ok = 1; |
266 | |
267 | c.g = getgroup(v[0].buf); c.h = ghash_byname(v[1].buf); |
268 | c.p = getge(c.g, v[2].buf); |
269 | s.r = (octet *)v[4].buf; s.s = *(mp **)v[5].buf; |
270 | erc = *(int *)v[6].buf; |
271 | |
272 | h = gkcdsa_beginhash(&c); |
273 | GH_HASH(h, v[3].buf, v[3].len); |
274 | gkcdsa_endhash(&c, h); |
275 | rc = gkcdsa_verify(&c, &s, GH_DONE(h, 0)); |
276 | if (!rc != !erc) { |
277 | ok = 0; |
278 | fprintf(stderr, "*** verify failed!\n"); |
279 | fprintf(stderr, "*** group: %s\n", v[0].buf); |
280 | fprintf(stderr, "*** hash: %s\n", c.h->name); |
281 | showge(c.g, "public key", c.p); |
282 | fprintf(stderr, "*** message: `%s'\n", v[3].buf); |
283 | fprintf(stderr, "*** sig r = "); |
284 | type_hex.dump(&v[4], stderr); putc('\n', stderr); |
285 | showmp("sig s", s.s, 16); |
286 | fprintf(stderr, "*** expected %s\n", !erc ? "pass" : "fail"); |
287 | } |
288 | mp_drop(s.s); G_DESTROY(c.g, c.p); G_DESTROYGROUP(c.g); |
289 | GH_DESTROY(h); |
290 | assert(mparena_count(MPARENA_GLOBAL) == 0); |
291 | return (ok); |
292 | } |
293 | |
294 | static const test_chunk tests[] = { |
295 | { "sign", tsign, { &type_string, &type_string, &type_mp, &type_string, |
296 | &type_mp, &type_hex, &type_mp } }, |
297 | { "verify", tverify, { &type_string, &type_string, &type_string, |
298 | &type_string, &type_hex, &type_mp, &type_int } }, |
299 | { 0 } |
300 | }; |
301 | |
302 | int main(int argc, char *argv[]) |
303 | { |
304 | sub_init(); |
305 | test_run(argc, argv, tests, SRCDIR "/tests/gkcdsa"); |
306 | return (0); |
307 | } |
308 | |
309 | #endif |
310 | |
311 | /*----- That's all, folks -------------------------------------------------*/ |