2 Blind-ID library for user identification using RSA blind signatures
3 Copyright (C) 2010 Rudolf Polzer
5 This library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 This library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with this library; if not, write to the Free Software
17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
20 #include "d0_blind_id.h"
24 #include "d0_bignum.h"
27 // for zero knowledge, we need multiple instances of schnorr ID scheme... should normally be sequential
28 // parallel schnorr ID is not provably zero knowledge :(
29 // (evil verifier can know all questions in advance, so sequential is disadvantage for him)
30 // we'll just live with a 1:1048576 chance of cheating, and support reauthenticating
32 #define SCHNORR_BITS 20
33 // probability of cheat: 2^(-bits+1)
35 #define SCHNORR_HASHSIZE 3
36 // cannot be >= SHA_DIGEST_LENGTH
37 // *8 must be >= SCHNORR_BITS
39 #define MSGSIZE 640 // ought to be enough for anyone
43 // signing (Xonotic pub and priv key)
44 d0_bignum_t *rsa_n, *rsa_e, *rsa_d;
46 // public data (Schnorr ID)
47 d0_bignum_t *schnorr_G;
49 // private data (player ID private key)
50 d0_bignum_t *schnorr_s;
52 // public data (player ID public key, this is what the server gets to know)
53 d0_bignum_t *schnorr_4_to_s;
54 d0_bignum_t *schnorr_4_to_s_signature;
57 d0_bignum_t *rn; // random number blind signature
58 d0_bignum_t *r; // random number for schnorr ID
59 char xnbh[SCHNORR_HASHSIZE]; // init hash
60 d0_bignum_t *e; // challenge
61 char msg[MSGSIZE]; // message
62 size_t msglen; // message length
65 #define CHECK(x) do { if(!(x)) goto fail; } while(0)
66 #define CHECK_ASSIGN(var, value) do { d0_bignum_t *val; val = value; if(!val) goto fail; var = val; } while(0)
68 static d0_bignum_t *zero, *one, *four, *temp0, *temp1, *temp2, *temp3, *temp4;
70 void d0_blind_id_INITIALIZE()
72 d0_bignum_INITIALIZE();
73 CHECK_ASSIGN(zero, d0_bignum_int(zero, 0));
74 CHECK_ASSIGN(one, d0_bignum_int(one, 1));
75 CHECK_ASSIGN(four, d0_bignum_int(four, 4));
76 CHECK_ASSIGN(temp0, d0_bignum_int(temp0, 0));
77 CHECK_ASSIGN(temp1, d0_bignum_int(temp1, 0));
78 CHECK_ASSIGN(temp2, d0_bignum_int(temp2, 0));
79 CHECK_ASSIGN(temp3, d0_bignum_int(temp3, 0));
80 CHECK_ASSIGN(temp4, d0_bignum_int(temp4, 0));
85 void d0_blind_id_SHUTDOWN()
90 d0_bignum_free(temp0);
91 d0_bignum_free(temp1);
92 d0_bignum_free(temp2);
93 d0_bignum_free(temp3);
94 d0_bignum_free(temp4);
99 d0_bignum_t *d0_dl_get_order(d0_bignum_t *o, const d0_bignum_t *G)
101 CHECK_ASSIGN(o, d0_bignum_sub(o, G, one));
102 CHECK(d0_bignum_shl(o, o, -1)); // order o = (G-1)/2
108 d0_bignum_t *d0_dl_get_from_order(d0_bignum_t *G, const d0_bignum_t *o)
110 CHECK_ASSIGN(G, d0_bignum_shl(G, o, 1));
111 CHECK(d0_bignum_add(G, G, one));
117 BOOL d0_dl_generate_key(size_t size, d0_bignum_t *G)
124 CHECK(d0_bignum_rand_bit_exact(temp0, size-1));
125 if(d0_bignum_isprime(temp0, 0) == 0)
127 CHECK(d0_dl_get_from_order(G, temp0));
128 if(d0_bignum_isprime(G, 10) == 0)
130 if(d0_bignum_isprime(temp0, 10) == 0) // finish the previous test
139 BOOL d0_rsa_generate_key(size_t size, const d0_bignum_t *e, d0_bignum_t *d, d0_bignum_t *n)
141 // uses temp0 to temp4
146 int pb = (size + 1)/2;
150 CHECK(d0_bignum_rand_bit_exact(temp0, pb));
151 if(d0_bignum_isprime(temp0, 10) == 0)
153 CHECK(d0_bignum_sub(temp2, temp0, one));
154 CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp2, e));
155 if(!d0_bignum_cmp(temp4, one))
164 CHECK(d0_bignum_rand_bit_exact(temp1, qb));
165 if(!d0_bignum_cmp(temp1, temp0))
171 if(d0_bignum_isprime(temp1, 10) == 0)
173 CHECK(d0_bignum_sub(temp3, temp1, one));
174 CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp3, e));
175 if(!d0_bignum_cmp(temp4, one))
183 CHECK(d0_bignum_mul(n, temp0, temp1));
185 // d = e^-1 mod (temp0-1)(temp1-1)
186 CHECK(d0_bignum_mul(temp0, temp2, temp3));
187 CHECK(d0_bignum_mod_inv(d, e, temp0));
193 void d0_blind_id_clear(d0_blind_id_t *ctx)
195 if(ctx->rsa_n) d0_bignum_free(ctx->rsa_n);
196 if(ctx->rsa_e) d0_bignum_free(ctx->rsa_e);
197 if(ctx->rsa_d) d0_bignum_free(ctx->rsa_d);
198 if(ctx->schnorr_G) d0_bignum_free(ctx->schnorr_G);
199 if(ctx->schnorr_s) d0_bignum_free(ctx->schnorr_s);
200 if(ctx->schnorr_4_to_s) d0_bignum_free(ctx->schnorr_4_to_s);
201 if(ctx->schnorr_4_to_s_signature) d0_bignum_free(ctx->schnorr_4_to_s_signature);
202 if(ctx->rn) d0_bignum_free(ctx->rn);
203 if(ctx->r) d0_bignum_free(ctx->r);
204 if(ctx->e) d0_bignum_free(ctx->e);
205 memset(ctx, 0, sizeof(*ctx));
208 void d0_blind_id_copy(d0_blind_id_t *ctx, const d0_blind_id_t *src)
210 d0_blind_id_clear(ctx);
211 if(src->rsa_n) ctx->rsa_n = d0_bignum_mov(NULL, src->rsa_n);
212 if(src->rsa_e) ctx->rsa_e = d0_bignum_mov(NULL, src->rsa_e);
213 if(src->rsa_d) ctx->rsa_d = d0_bignum_mov(NULL, src->rsa_d);
214 if(src->schnorr_G) ctx->schnorr_G = d0_bignum_mov(NULL, src->schnorr_G);
215 if(src->schnorr_s) ctx->schnorr_s = d0_bignum_mov(NULL, src->schnorr_s);
216 if(src->schnorr_4_to_s) ctx->schnorr_4_to_s = d0_bignum_mov(NULL, ctx->schnorr_G);
217 if(src->schnorr_4_to_s_signature) ctx->schnorr_4_to_s_signature = d0_bignum_mov(NULL, src->schnorr_4_to_s_signature);
218 if(src->rn) ctx->rn = d0_bignum_mov(NULL, src->rn);
219 if(src->r) ctx->r = d0_bignum_mov(NULL, src->r);
220 if(src->e) ctx->e = d0_bignum_mov(NULL, src->e);
221 // TODO xnbh, msg, msglen?
224 WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_keys(d0_blind_id_t *ctx, int k)
226 d0_blind_id_clear(ctx);
227 CHECK_ASSIGN(ctx->schnorr_G, d0_bignum_new());
228 CHECK(d0_dl_generate_key(k, ctx->schnorr_G));
229 CHECK_ASSIGN(ctx->rsa_e, d0_bignum_int(NULL, 65537));
230 CHECK_ASSIGN(ctx->rsa_d, d0_bignum_new());
231 CHECK_ASSIGN(ctx->rsa_n, d0_bignum_new());
232 CHECK(d0_rsa_generate_key(k+1, ctx->rsa_e, ctx->rsa_d, ctx->rsa_n)); // must fit G for sure
238 WARN_UNUSED_RESULT BOOL d0_blind_id_read_private_keys(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
240 d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
241 d0_blind_id_clear(ctx);
242 CHECK_ASSIGN(ctx->schnorr_G, d0_iobuf_read_bignum(in, NULL));
243 CHECK_ASSIGN(ctx->rsa_n, d0_iobuf_read_bignum(in, NULL));
244 CHECK_ASSIGN(ctx->rsa_e, d0_iobuf_read_bignum(in, NULL));
245 CHECK_ASSIGN(ctx->rsa_d, d0_iobuf_read_bignum(in, NULL));
246 return d0_iobuf_close(in, NULL);
249 d0_iobuf_close(in, NULL);
253 WARN_UNUSED_RESULT BOOL d0_blind_id_read_public_keys(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
255 d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
256 d0_blind_id_clear(ctx);
257 CHECK_ASSIGN(ctx->schnorr_G, d0_iobuf_read_bignum(in, NULL));
258 CHECK_ASSIGN(ctx->rsa_n, d0_iobuf_read_bignum(in, NULL));
259 CHECK_ASSIGN(ctx->rsa_e, d0_iobuf_read_bignum(in, NULL));
260 return d0_iobuf_close(in, NULL);
263 d0_iobuf_close(in, NULL);
267 #define USING(x) if(!(ctx->x)) return 0
268 #define WRITING(x,f) if(ctx->x) { f(ctx->x); ctx->x = NULL; }
271 WARN_UNUSED_RESULT BOOL d0_blind_id_write_private_keys(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
273 USING(rsa_n); USING(rsa_e); USING(rsa_d);
275 d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
276 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
277 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_n));
278 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_e));
279 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_d));
280 return d0_iobuf_close(out, outbuflen);
283 d0_iobuf_close(out, outbuflen);
287 WARN_UNUSED_RESULT BOOL d0_blind_id_write_public_keys(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
289 USING(rsa_n); USING(rsa_e); USING(rsa_d);
291 d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
292 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
293 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_n));
294 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_e));
295 return d0_iobuf_close(out, outbuflen);
298 if(!d0_iobuf_close(out, outbuflen))
303 WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_id_start(d0_blind_id_t *ctx)
305 // temps: temp0 order
307 REPLACING(schnorr_s); REPLACING(schnorr_4_to_s);
309 CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
310 CHECK_ASSIGN(ctx->schnorr_s, d0_bignum_rand_range(ctx->schnorr_s, zero, temp0));
311 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_bignum_mod_pow(ctx->schnorr_4_to_s, four, ctx->schnorr_s, ctx->schnorr_G));
318 WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_id_request(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
320 // temps: temp0 temp1
321 USING(rsa_n); USING(rsa_e); USING(schnorr_4_to_s);
324 d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
326 CHECK_ASSIGN(ctx->rn, d0_bignum_rand_bit_atmost(ctx->rn, d0_bignum_size(ctx->rsa_n)));
327 CHECK(d0_bignum_mod_pow(temp0, ctx->rn, ctx->rsa_e, ctx->rsa_n));
328 CHECK(d0_bignum_mod_mul(temp1, ctx->schnorr_4_to_s, temp0, ctx->rsa_n));
329 CHECK(d0_iobuf_write_bignum(out, temp1));
330 return d0_iobuf_close(out, outbuflen);
333 d0_iobuf_close(out, outbuflen);
337 WARN_UNUSED_RESULT BOOL d0_blind_id_answer_private_id_request(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen)
339 // temps: temp0 temp1
340 USING(rsa_d); USING(rsa_n);
342 d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
343 d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
345 CHECK(d0_iobuf_read_bignum(in, temp0));
346 CHECK(d0_bignum_mod_pow(temp1, temp0, ctx->rsa_d, ctx->rsa_n));
347 CHECK(d0_iobuf_write_bignum(out, temp1));
349 d0_iobuf_close(in, NULL);
350 return d0_iobuf_close(out, outbuflen);
353 d0_iobuf_close(in, NULL);
354 d0_iobuf_close(out, outbuflen);
358 WARN_UNUSED_RESULT BOOL d0_blind_id_finish_private_id_request(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
360 // temps: temp0 temp1
361 USING(rn); USING(rsa_n);
362 REPLACING(schnorr_4_to_s_signature);
364 d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
366 CHECK(d0_iobuf_read_bignum(in, temp0));
367 CHECK(d0_bignum_mod_inv(temp1, ctx->rn, ctx->rsa_n));
368 CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_bignum_mod_mul(ctx->schnorr_4_to_s_signature, temp0, temp1, ctx->rsa_n));
370 return d0_iobuf_close(in, NULL);
373 d0_iobuf_close(in, NULL);
377 WARN_UNUSED_RESULT BOOL d0_blind_id_read_private_id(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
379 REPLACING(schnorr_s); REPLACING(schnorr_4_to_s); REPLACING(schnorr_4_to_s_signature);
381 d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
383 CHECK_ASSIGN(ctx->schnorr_s, d0_iobuf_read_bignum(in, ctx->schnorr_s));
384 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s));
385 CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s_signature));
387 return d0_iobuf_close(in, NULL);
390 d0_iobuf_close(in, NULL);
394 WARN_UNUSED_RESULT BOOL d0_blind_id_read_public_id(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
396 REPLACING(schnorr_4_to_s); REPLACING(schnorr_4_to_s_signature);
398 d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
400 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s));
401 CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s_signature));
403 return d0_iobuf_close(in, NULL);
406 d0_iobuf_close(in, NULL);
410 WARN_UNUSED_RESULT BOOL d0_blind_id_write_private_id(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
412 USING(schnorr_s); USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
414 d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
416 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_s));
417 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
418 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s_signature));
420 return d0_iobuf_close(out, outbuflen);
423 d0_iobuf_close(out, outbuflen);
427 WARN_UNUSED_RESULT BOOL d0_blind_id_write_public_id(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
429 USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
431 d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
433 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
434 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s_signature));
436 return d0_iobuf_close(out, outbuflen);
439 d0_iobuf_close(out, outbuflen);
443 WARN_UNUSED_RESULT BOOL d0_blind_id_authenticate_with_private_id_start(d0_blind_id_t *ctx, int is_first, char *msg, size_t msglen, char *outbuf, size_t *outbuflen)
445 // first run: send 4^s, 4^s signature
446 // 1. get random r, send HASH(4^r)
450 USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
455 d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
460 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
461 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s_signature));
464 // start schnorr ID scheme
465 // generate random number r; x = g^r; send hash of x, remember r, forget x
466 CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
467 CHECK_ASSIGN(ctx->r, d0_bignum_rand_range(ctx->r, zero, temp0));
468 CHECK(d0_bignum_mod_pow(temp0, four, ctx->r, ctx->schnorr_G));
470 // hash it, hash it, everybody hash it
471 unsigned char convbuf[1024];
472 d0_iobuf_t *conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
474 CHECK(d0_iobuf_write_bignum(conv, temp0));
475 CHECK(d0_iobuf_write_packet(conv, msg, msglen));
476 CHECK(d0_iobuf_write_bignum(conv, temp0));
477 d0_iobuf_close(conv, &sz);
479 CHECK(d0_iobuf_write_raw(out, sha(convbuf, sz), SCHNORR_HASHSIZE) == SCHNORR_HASHSIZE);
480 CHECK(d0_iobuf_write_packet(out, msg, msglen));
482 return d0_iobuf_close(out, outbuflen);
485 d0_iobuf_close(out, outbuflen);
489 WARN_UNUSED_RESULT BOOL d0_blind_id_authenticate_with_private_id_challenge(d0_blind_id_t *ctx, int is_first, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen)
490 // first run: get 4^s, 4^s signature
493 // 3. send challenge e of SCHNORR_BITS
497 REPLACING(schnorr_4_to_s); REPLACING(k); REPLACING(schnorr_4_to_s_signature);
498 USING(schnorr_G); USING(rsa_n);
502 USING(schnorr_4_to_s_signature); USING(schnorr_4_to_s);
504 USING(rsa_e); USING(rsa_n);
505 REPLACING(e); REPLACING(msg); REPLACING(msglen);
507 d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
508 d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
512 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, NULL));
513 CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s, zero) >= 0);
514 CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s, ctx->schnorr_G) < 0);
515 CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s_signature));
516 CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s_signature, zero) >= 0);
517 CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s_signature, ctx->rsa_n) < 0);
520 // check signature of key (t = k^d, so, t^e = k)
521 CHECK(d0_bignum_mod_pow(temp0, ctx->schnorr_4_to_s_signature, ctx->rsa_e, ctx->rsa_n));
522 if(d0_bignum_cmp(temp0, ctx->schnorr_4_to_s))
524 // FAIL (not signed by Xonotic)
526 // TODO: accept the key anyway, but mark as failed signature!
529 CHECK(d0_iobuf_read_raw(in, ctx->xnbh, SCHNORR_HASHSIZE));
530 ctx->msglen = MSGSIZE;
531 CHECK(d0_iobuf_read_packet(in, ctx->msg, &ctx->msglen));
534 CHECK_ASSIGN(ctx->e, d0_bignum_rand_bit_atmost(ctx->e, SCHNORR_BITS));
536 CHECK(d0_iobuf_write_bignum(out, ctx->e));
538 d0_iobuf_close(in, NULL);
539 return d0_iobuf_close(out, outbuflen);
542 d0_iobuf_close(in, NULL);
543 d0_iobuf_close(out, outbuflen);
547 WARN_UNUSED_RESULT BOOL d0_blind_id_authenticate_with_private_id_response(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen)
548 // 1. read challenge e of SCHNORR_BITS
549 // 2. reply with r + s * e mod order
551 // temps: 0 order, 1 prod, 2 y, 3 e
552 USING(schnorr_G); USING(schnorr_s); USING(r);
554 d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
555 d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
557 CHECK(d0_iobuf_read_bignum(in, temp3));
558 // TODO check if >= 2^SCHNORR_BITS or < 0, if yes, then fail (needed for zero knowledge)
559 CHECK(d0_bignum_cmp(temp3, zero) >= 0);
560 CHECK(d0_bignum_size(temp3) <= SCHNORR_BITS);
562 // send response for schnorr ID scheme
563 // i.e. r + ctx->schnorr_s * temp3
564 CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
565 CHECK(d0_bignum_mod_mul(temp1, ctx->schnorr_s, temp3, temp0));
566 CHECK(d0_bignum_mod_add(temp2, temp1, ctx->r, temp0));
567 CHECK(d0_iobuf_write_bignum(out, temp2));
569 d0_iobuf_close(in, NULL);
570 return d0_iobuf_close(out, outbuflen);
573 d0_iobuf_close(in, NULL);
574 d0_iobuf_close(out, outbuflen);
578 WARN_UNUSED_RESULT BOOL d0_blind_id_authenticate_with_private_id_verify(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen, char *msg, ssize_t *msglen)
579 // 1. read y = r + s * e mod order
580 // 2. verify: g^y (g^s)^-e = g^(r+s*e-s*e) = g^r
581 // (check using H(g^r) which we know)
583 // temps: 0 y 1 order
584 USING(e); USING(schnorr_G);
586 d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
589 CHECK(d0_dl_get_order(temp1, ctx->schnorr_G));
590 CHECK(d0_iobuf_read_bignum(in, temp0));
591 CHECK(d0_bignum_cmp(temp0, zero) >= 0);
592 CHECK(d0_bignum_cmp(temp0, temp1) < 0);
594 // verify schnorr ID scheme
595 // we need 4^temp0 (g^s)^-e
596 CHECK(d0_bignum_neg(temp1, ctx->e));
597 CHECK(d0_bignum_mod_pow(temp2, ctx->schnorr_4_to_s, temp1, ctx->schnorr_G));
598 CHECK(d0_bignum_mod_pow(temp1, four, temp0, ctx->schnorr_G));
599 CHECK(d0_bignum_mod_mul(temp3, temp1, temp2, ctx->schnorr_G));
600 // hash must be equal to xnbh
602 // hash it, hash it, everybody hash it
603 unsigned char convbuf[1024];
604 d0_iobuf_t *conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
606 CHECK(d0_iobuf_write_bignum(conv, temp3));
607 CHECK(d0_iobuf_write_packet(conv, ctx->msg, ctx->msglen));
608 CHECK(d0_iobuf_write_bignum(conv, temp3));
609 d0_iobuf_close(conv, &sz);
611 if(memcmp(sha(convbuf, sz), ctx->xnbh, SCHNORR_HASHSIZE))
613 // FAIL (not owned by player)
617 if(ctx->msglen <= (size_t) *msglen)
618 memcpy(msg, ctx->msg, ctx->msglen);
620 memcpy(msg, ctx->msg, *msglen);
621 *msglen = ctx->msglen;
623 d0_iobuf_close(in, NULL);
627 d0_iobuf_close(in, NULL);
631 WARN_UNUSED_RESULT BOOL d0_blind_id_fingerprint64_public_id(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
633 USING(schnorr_4_to_s);
635 static unsigned char convbuf[1024];
636 d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
637 d0_iobuf_t *conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
641 CHECK(d0_iobuf_write_bignum(conv, ctx->schnorr_4_to_s));
642 CHECK(d0_iobuf_close(conv, &sz));
645 n = (*outbuflen / 4) * 3;
646 if(n > SHA_DIGESTSIZE)
648 if(d0_iobuf_write_raw(out, sha(convbuf, sz), n) != n)
650 if(!d0_iobuf_conv_base64_out(out))
653 return d0_iobuf_close(out, outbuflen);
657 if(!d0_iobuf_close(conv, &sz)) { }
658 if(!d0_iobuf_close(out, outbuflen))
663 d0_blind_id_t *d0_blind_id_new()
665 d0_blind_id_t *b = d0_malloc(sizeof(d0_blind_id_t));
666 memset(b, 0, sizeof(*b));
670 void d0_blind_id_free(d0_blind_id_t *a)
672 d0_blind_id_clear(a);