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; // 0 when signature is invalid
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(void)
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(void)
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
144 int pb = (size + 1)/2;
152 CHECK(d0_bignum_rand_bit_exact(temp0, pb));
153 if(d0_bignum_isprime(temp0, 10) == 0)
155 CHECK(d0_bignum_sub(temp2, temp0, one));
156 CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp2, e));
157 if(!d0_bignum_cmp(temp4, one))
166 CHECK(d0_bignum_rand_bit_exact(temp1, qb));
167 if(!d0_bignum_cmp(temp1, temp0))
173 if(d0_bignum_isprime(temp1, 10) == 0)
175 CHECK(d0_bignum_sub(temp3, temp1, one));
176 CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp3, e));
177 if(!d0_bignum_cmp(temp4, one))
185 CHECK(d0_bignum_mul(n, temp0, temp1));
187 // d = e^-1 mod (temp0-1)(temp1-1)
188 CHECK(d0_bignum_mul(temp0, temp2, temp3));
189 CHECK(d0_bignum_mod_inv(d, e, temp0));
195 void d0_blind_id_clear(d0_blind_id_t *ctx)
197 if(ctx->rsa_n) d0_bignum_free(ctx->rsa_n);
198 if(ctx->rsa_e) d0_bignum_free(ctx->rsa_e);
199 if(ctx->rsa_d) d0_bignum_free(ctx->rsa_d);
200 if(ctx->schnorr_G) d0_bignum_free(ctx->schnorr_G);
201 if(ctx->schnorr_s) d0_bignum_free(ctx->schnorr_s);
202 if(ctx->schnorr_4_to_s) d0_bignum_free(ctx->schnorr_4_to_s);
203 if(ctx->schnorr_4_to_s_signature) d0_bignum_free(ctx->schnorr_4_to_s_signature);
204 if(ctx->rn) d0_bignum_free(ctx->rn);
205 if(ctx->r) d0_bignum_free(ctx->r);
206 if(ctx->e) d0_bignum_free(ctx->e);
207 memset(ctx, 0, sizeof(*ctx));
210 void d0_blind_id_copy(d0_blind_id_t *ctx, const d0_blind_id_t *src)
212 d0_blind_id_clear(ctx);
213 if(src->rsa_n) ctx->rsa_n = d0_bignum_mov(NULL, src->rsa_n);
214 if(src->rsa_e) ctx->rsa_e = d0_bignum_mov(NULL, src->rsa_e);
215 if(src->rsa_d) ctx->rsa_d = d0_bignum_mov(NULL, src->rsa_d);
216 if(src->schnorr_G) ctx->schnorr_G = d0_bignum_mov(NULL, src->schnorr_G);
217 if(src->schnorr_s) ctx->schnorr_s = d0_bignum_mov(NULL, src->schnorr_s);
218 if(src->schnorr_4_to_s) ctx->schnorr_4_to_s = d0_bignum_mov(NULL, ctx->schnorr_G);
219 if(src->schnorr_4_to_s_signature) ctx->schnorr_4_to_s_signature = d0_bignum_mov(NULL, src->schnorr_4_to_s_signature);
220 if(src->rn) ctx->rn = d0_bignum_mov(NULL, src->rn);
221 if(src->r) ctx->r = d0_bignum_mov(NULL, src->r);
222 if(src->e) ctx->e = d0_bignum_mov(NULL, src->e);
223 // TODO xnbh, msg, msglen?
226 WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_keys(d0_blind_id_t *ctx, int k)
228 d0_blind_id_clear(ctx);
229 CHECK_ASSIGN(ctx->schnorr_G, d0_bignum_new());
230 CHECK(d0_dl_generate_key(k, ctx->schnorr_G));
231 CHECK_ASSIGN(ctx->rsa_e, d0_bignum_int(NULL, 65537));
232 CHECK_ASSIGN(ctx->rsa_d, d0_bignum_new());
233 CHECK_ASSIGN(ctx->rsa_n, d0_bignum_new());
234 CHECK(d0_rsa_generate_key(k+1, ctx->rsa_e, ctx->rsa_d, ctx->rsa_n)); // must fit G for sure
240 WARN_UNUSED_RESULT BOOL d0_blind_id_read_private_keys(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
242 d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
243 d0_blind_id_clear(ctx);
244 CHECK_ASSIGN(ctx->schnorr_G, d0_iobuf_read_bignum(in, NULL));
245 CHECK_ASSIGN(ctx->rsa_n, d0_iobuf_read_bignum(in, NULL));
246 CHECK_ASSIGN(ctx->rsa_e, d0_iobuf_read_bignum(in, NULL));
247 CHECK_ASSIGN(ctx->rsa_d, d0_iobuf_read_bignum(in, NULL));
248 return d0_iobuf_close(in, NULL);
251 d0_iobuf_close(in, NULL);
255 WARN_UNUSED_RESULT BOOL d0_blind_id_read_public_keys(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
257 d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
258 d0_blind_id_clear(ctx);
259 CHECK_ASSIGN(ctx->schnorr_G, d0_iobuf_read_bignum(in, NULL));
260 CHECK_ASSIGN(ctx->rsa_n, d0_iobuf_read_bignum(in, NULL));
261 CHECK_ASSIGN(ctx->rsa_e, d0_iobuf_read_bignum(in, NULL));
262 return d0_iobuf_close(in, NULL);
265 d0_iobuf_close(in, NULL);
269 #define USING(x) if(!(ctx->x)) return 0
272 WARN_UNUSED_RESULT BOOL d0_blind_id_write_private_keys(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
276 USING(rsa_n); USING(rsa_e); USING(rsa_d);
278 out = d0_iobuf_open_write(outbuf, *outbuflen);
279 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
280 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_n));
281 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_e));
282 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_d));
283 return d0_iobuf_close(out, outbuflen);
286 d0_iobuf_close(out, outbuflen);
290 WARN_UNUSED_RESULT BOOL d0_blind_id_write_public_keys(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
294 USING(rsa_n); USING(rsa_e); USING(rsa_d);
296 out = d0_iobuf_open_write(outbuf, *outbuflen);
297 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
298 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_n));
299 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_e));
300 return d0_iobuf_close(out, outbuflen);
303 if(!d0_iobuf_close(out, outbuflen))
308 WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_id_start(d0_blind_id_t *ctx)
310 // temps: temp0 order
312 REPLACING(schnorr_s); REPLACING(schnorr_4_to_s);
314 CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
315 CHECK_ASSIGN(ctx->schnorr_s, d0_bignum_rand_range(ctx->schnorr_s, zero, temp0));
316 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_bignum_mod_pow(ctx->schnorr_4_to_s, four, ctx->schnorr_s, ctx->schnorr_G));
317 CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_bignum_zero(ctx->schnorr_4_to_s_signature));
324 WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_id_request(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
328 // temps: temp0 temp1
329 USING(rsa_n); USING(rsa_e); USING(schnorr_4_to_s);
332 out = d0_iobuf_open_write(outbuf, *outbuflen);
334 CHECK_ASSIGN(ctx->rn, d0_bignum_rand_bit_atmost(ctx->rn, d0_bignum_size(ctx->rsa_n)));
335 CHECK(d0_bignum_mod_pow(temp0, ctx->rn, ctx->rsa_e, ctx->rsa_n));
336 CHECK(d0_bignum_mod_mul(temp1, ctx->schnorr_4_to_s, temp0, ctx->rsa_n));
337 CHECK(d0_iobuf_write_bignum(out, temp1));
338 return d0_iobuf_close(out, outbuflen);
341 d0_iobuf_close(out, outbuflen);
345 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)
350 // temps: temp0 temp1
351 USING(rsa_d); USING(rsa_n);
353 in = d0_iobuf_open_read(inbuf, inbuflen);
354 out = d0_iobuf_open_write(outbuf, *outbuflen);
356 CHECK(d0_iobuf_read_bignum(in, temp0));
357 CHECK(d0_bignum_mod_pow(temp1, temp0, ctx->rsa_d, ctx->rsa_n));
358 CHECK(d0_iobuf_write_bignum(out, temp1));
360 d0_iobuf_close(in, NULL);
361 return d0_iobuf_close(out, outbuflen);
364 d0_iobuf_close(in, NULL);
365 d0_iobuf_close(out, outbuflen);
369 WARN_UNUSED_RESULT BOOL d0_blind_id_finish_private_id_request(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
373 // temps: temp0 temp1
374 USING(rn); USING(rsa_n);
375 REPLACING(schnorr_4_to_s_signature);
377 in = d0_iobuf_open_read(inbuf, inbuflen);
379 CHECK(d0_iobuf_read_bignum(in, temp0));
380 CHECK(d0_bignum_mod_inv(temp1, ctx->rn, ctx->rsa_n));
381 CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_bignum_mod_mul(ctx->schnorr_4_to_s_signature, temp0, temp1, ctx->rsa_n));
383 return d0_iobuf_close(in, NULL);
386 d0_iobuf_close(in, NULL);
390 WARN_UNUSED_RESULT BOOL d0_blind_id_read_private_id(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
394 REPLACING(schnorr_s); REPLACING(schnorr_4_to_s); REPLACING(schnorr_4_to_s_signature);
396 in = d0_iobuf_open_read(inbuf, inbuflen);
398 CHECK_ASSIGN(ctx->schnorr_s, d0_iobuf_read_bignum(in, ctx->schnorr_s));
399 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s));
400 CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s_signature));
402 return d0_iobuf_close(in, NULL);
405 d0_iobuf_close(in, NULL);
409 WARN_UNUSED_RESULT BOOL d0_blind_id_read_public_id(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
413 REPLACING(schnorr_4_to_s); REPLACING(schnorr_4_to_s_signature);
415 in = d0_iobuf_open_read(inbuf, inbuflen);
417 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s));
418 CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s_signature));
420 return d0_iobuf_close(in, NULL);
423 d0_iobuf_close(in, NULL);
427 WARN_UNUSED_RESULT BOOL d0_blind_id_write_private_id(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
431 USING(schnorr_s); USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
433 out = d0_iobuf_open_write(outbuf, *outbuflen);
435 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_s));
436 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
437 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s_signature));
439 return d0_iobuf_close(out, outbuflen);
442 d0_iobuf_close(out, outbuflen);
446 WARN_UNUSED_RESULT BOOL d0_blind_id_write_public_id(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
450 USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
452 out = d0_iobuf_open_write(outbuf, *outbuflen);
454 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
455 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s_signature));
457 return d0_iobuf_close(out, outbuflen);
460 d0_iobuf_close(out, outbuflen);
464 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)
466 // first run: send 4^s, 4^s signature
467 // 1. get random r, send HASH(4^r)
470 unsigned char convbuf[1024];
476 USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
481 out = d0_iobuf_open_write(outbuf, *outbuflen);
486 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
487 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s_signature));
490 // start schnorr ID scheme
491 // generate random number r; x = g^r; send hash of x, remember r, forget x
492 CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
493 CHECK_ASSIGN(ctx->r, d0_bignum_rand_range(ctx->r, zero, temp0));
494 CHECK(d0_bignum_mod_pow(temp0, four, ctx->r, ctx->schnorr_G));
496 // hash it, hash it, everybody hash it
497 conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
498 CHECK(d0_iobuf_write_bignum(conv, temp0));
499 CHECK(d0_iobuf_write_packet(conv, msg, msglen));
500 CHECK(d0_iobuf_write_bignum(conv, temp0));
501 d0_iobuf_close(conv, &sz);
503 CHECK(d0_iobuf_write_raw(out, sha(convbuf, sz), SCHNORR_HASHSIZE) == SCHNORR_HASHSIZE);
504 CHECK(d0_iobuf_write_packet(out, msg, msglen));
506 return d0_iobuf_close(out, outbuflen);
509 d0_iobuf_close(out, outbuflen);
513 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, BOOL *status)
514 // first run: get 4^s, 4^s signature
517 // 3. send challenge e of SCHNORR_BITS
524 REPLACING(schnorr_4_to_s); REPLACING(k); REPLACING(schnorr_4_to_s_signature);
525 USING(schnorr_G); USING(rsa_n);
529 USING(schnorr_4_to_s_signature); USING(schnorr_4_to_s);
531 USING(rsa_e); USING(rsa_n);
532 REPLACING(e); REPLACING(msg); REPLACING(msglen);
534 in = d0_iobuf_open_read(inbuf, inbuflen);
535 out = d0_iobuf_open_write(outbuf, *outbuflen);
539 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, NULL));
540 CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s, zero) >= 0);
541 CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s, ctx->schnorr_G) < 0);
542 CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s_signature));
543 CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s_signature, zero) >= 0);
544 CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s_signature, ctx->rsa_n) < 0);
546 // check signature of key (t = k^d, so, t^e = k)
547 CHECK(d0_bignum_mod_pow(temp0, ctx->schnorr_4_to_s_signature, ctx->rsa_e, ctx->rsa_n));
548 if(d0_bignum_cmp(temp0, ctx->schnorr_4_to_s))
550 // accept the key anyway, but mark as failed signature! will later return 0 in status
551 CHECK(d0_bignum_zero(ctx->schnorr_4_to_s_signature));
555 CHECK(d0_iobuf_read_raw(in, ctx->xnbh, SCHNORR_HASHSIZE));
556 ctx->msglen = MSGSIZE;
557 CHECK(d0_iobuf_read_packet(in, ctx->msg, &ctx->msglen));
560 CHECK_ASSIGN(ctx->e, d0_bignum_rand_bit_atmost(ctx->e, SCHNORR_BITS));
562 CHECK(d0_iobuf_write_bignum(out, ctx->e));
565 *status = !!d0_bignum_cmp(ctx->schnorr_4_to_s_signature, zero);
567 d0_iobuf_close(in, NULL);
568 return d0_iobuf_close(out, outbuflen);
571 d0_iobuf_close(in, NULL);
572 d0_iobuf_close(out, outbuflen);
576 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)
577 // 1. read challenge e of SCHNORR_BITS
578 // 2. reply with r + s * e mod order
583 // temps: 0 order, 1 prod, 2 y, 3 e
584 USING(schnorr_G); USING(schnorr_s); USING(r);
586 in = d0_iobuf_open_read(inbuf, inbuflen);
587 out = d0_iobuf_open_write(outbuf, *outbuflen);
589 CHECK(d0_iobuf_read_bignum(in, temp3));
590 // TODO check if >= 2^SCHNORR_BITS or < 0, if yes, then fail (needed for zero knowledge)
591 CHECK(d0_bignum_cmp(temp3, zero) >= 0);
592 CHECK(d0_bignum_size(temp3) <= SCHNORR_BITS);
594 // send response for schnorr ID scheme
595 // i.e. r + ctx->schnorr_s * temp3
596 CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
597 CHECK(d0_bignum_mod_mul(temp1, ctx->schnorr_s, temp3, temp0));
598 CHECK(d0_bignum_mod_add(temp2, temp1, ctx->r, temp0));
599 CHECK(d0_iobuf_write_bignum(out, temp2));
601 d0_iobuf_close(in, NULL);
602 return d0_iobuf_close(out, outbuflen);
605 d0_iobuf_close(in, NULL);
606 d0_iobuf_close(out, outbuflen);
610 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, BOOL *status)
611 // 1. read y = r + s * e mod order
612 // 2. verify: g^y (g^s)^-e = g^(r+s*e-s*e) = g^r
613 // (check using H(g^r) which we know)
616 unsigned char convbuf[1024];
620 // temps: 0 y 1 order
621 USING(e); USING(schnorr_G);
623 in = d0_iobuf_open_read(inbuf, inbuflen);
626 CHECK(d0_dl_get_order(temp1, ctx->schnorr_G));
627 CHECK(d0_iobuf_read_bignum(in, temp0));
628 CHECK(d0_bignum_cmp(temp0, zero) >= 0);
629 CHECK(d0_bignum_cmp(temp0, temp1) < 0);
631 // verify schnorr ID scheme
632 // we need 4^temp0 (g^s)^-e
633 CHECK(d0_bignum_neg(temp1, ctx->e));
634 CHECK(d0_bignum_mod_pow(temp2, ctx->schnorr_4_to_s, temp1, ctx->schnorr_G));
635 CHECK(d0_bignum_mod_pow(temp1, four, temp0, ctx->schnorr_G));
636 CHECK(d0_bignum_mod_mul(temp3, temp1, temp2, ctx->schnorr_G));
637 // hash must be equal to xnbh
639 // hash it, hash it, everybody hash it
640 conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
641 CHECK(d0_iobuf_write_bignum(conv, temp3));
642 CHECK(d0_iobuf_write_packet(conv, ctx->msg, ctx->msglen));
643 CHECK(d0_iobuf_write_bignum(conv, temp3));
644 d0_iobuf_close(conv, &sz);
646 if(memcmp(sha(convbuf, sz), ctx->xnbh, SCHNORR_HASHSIZE))
648 // FAIL (not owned by player)
653 *status = !!d0_bignum_cmp(ctx->schnorr_4_to_s_signature, zero);
655 if(ctx->msglen <= (size_t) *msglen)
656 memcpy(msg, ctx->msg, ctx->msglen);
658 memcpy(msg, ctx->msg, *msglen);
659 *msglen = ctx->msglen;
661 d0_iobuf_close(in, NULL);
665 d0_iobuf_close(in, NULL);
669 WARN_UNUSED_RESULT BOOL d0_blind_id_fingerprint64_public_id(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
673 static unsigned char convbuf[1024];
676 USING(schnorr_4_to_s);
678 out = d0_iobuf_open_write(outbuf, *outbuflen);
679 conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
681 CHECK(d0_iobuf_write_bignum(conv, ctx->schnorr_4_to_s));
682 CHECK(d0_iobuf_close(conv, &sz));
685 n = (*outbuflen / 4) * 3;
686 if(n > SHA_DIGESTSIZE)
688 if(d0_iobuf_write_raw(out, sha(convbuf, sz), n) != n)
690 if(!d0_iobuf_conv_base64_out(out))
693 return d0_iobuf_close(out, outbuflen);
697 if(!d0_iobuf_close(conv, &sz)) { }
698 if(!d0_iobuf_close(out, outbuflen))
703 d0_blind_id_t *d0_blind_id_new(void)
705 d0_blind_id_t *b = d0_malloc(sizeof(d0_blind_id_t));
706 memset(b, 0, sizeof(*b));
710 void d0_blind_id_free(d0_blind_id_t *a)
712 d0_blind_id_clear(a);