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_key(d0_blind_id_t *ctx, int k)
228 d0_blind_id_clear(ctx);
229 CHECK_ASSIGN(ctx->rsa_e, d0_bignum_int(ctx->rsa_e, 65537));
230 CHECK_ASSIGN(ctx->rsa_d, d0_bignum_zero(ctx->rsa_d));
231 CHECK_ASSIGN(ctx->rsa_n, d0_bignum_zero(ctx->rsa_n));
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_key(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
240 d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
241 CHECK_ASSIGN(ctx->rsa_n, d0_iobuf_read_bignum(in, ctx->rsa_n));
242 CHECK_ASSIGN(ctx->rsa_e, d0_iobuf_read_bignum(in, ctx->rsa_e));
243 CHECK_ASSIGN(ctx->rsa_d, d0_iobuf_read_bignum(in, ctx->rsa_d));
244 return d0_iobuf_close(in, NULL);
247 d0_iobuf_close(in, NULL);
251 WARN_UNUSED_RESULT BOOL d0_blind_id_read_public_key(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
253 d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
254 CHECK_ASSIGN(ctx->rsa_n, d0_iobuf_read_bignum(in, ctx->rsa_n));
255 CHECK_ASSIGN(ctx->rsa_e, d0_iobuf_read_bignum(in, ctx->rsa_e));
256 return d0_iobuf_close(in, NULL);
259 d0_iobuf_close(in, NULL);
263 #define USING(x) if(!(ctx->x)) return 0
266 WARN_UNUSED_RESULT BOOL d0_blind_id_write_private_key(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
270 USING(rsa_n); USING(rsa_e); USING(rsa_d);
272 out = d0_iobuf_open_write(outbuf, *outbuflen);
273 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_n));
274 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_e));
275 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_d));
276 return d0_iobuf_close(out, outbuflen);
279 d0_iobuf_close(out, outbuflen);
283 WARN_UNUSED_RESULT BOOL d0_blind_id_write_public_key(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
287 USING(rsa_n); USING(rsa_e);
289 out = d0_iobuf_open_write(outbuf, *outbuflen);
290 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_n));
291 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_e));
292 return d0_iobuf_close(out, outbuflen);
295 if(!d0_iobuf_close(out, outbuflen))
300 WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_id_modulus(d0_blind_id_t *ctx)
303 REPLACING(schnorr_G);
305 CHECK_ASSIGN(ctx->schnorr_G, d0_bignum_zero(ctx->schnorr_G));
306 CHECK(d0_dl_generate_key(d0_bignum_size(ctx->rsa_n)-1, ctx->schnorr_G));
312 WARN_UNUSED_RESULT BOOL d0_blind_id_read_private_id_modulus(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
314 d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
315 CHECK_ASSIGN(ctx->schnorr_G, d0_iobuf_read_bignum(in, ctx->schnorr_G));
316 return d0_iobuf_close(in, NULL);
319 d0_iobuf_close(in, NULL);
323 WARN_UNUSED_RESULT BOOL d0_blind_id_write_private_id_modulus(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
329 out = d0_iobuf_open_write(outbuf, *outbuflen);
330 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
331 return d0_iobuf_close(out, outbuflen);
334 d0_iobuf_close(out, outbuflen);
338 WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_id_start(d0_blind_id_t *ctx)
340 // temps: temp0 order
342 REPLACING(schnorr_s); REPLACING(schnorr_4_to_s);
344 CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
345 CHECK_ASSIGN(ctx->schnorr_s, d0_bignum_rand_range(ctx->schnorr_s, zero, temp0));
346 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_bignum_mod_pow(ctx->schnorr_4_to_s, four, ctx->schnorr_s, ctx->schnorr_G));
347 CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_bignum_zero(ctx->schnorr_4_to_s_signature));
354 WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_id_request(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
358 // temps: temp0 temp1
359 USING(rsa_n); USING(rsa_e); USING(schnorr_4_to_s);
362 out = d0_iobuf_open_write(outbuf, *outbuflen);
364 CHECK_ASSIGN(ctx->rn, d0_bignum_rand_bit_atmost(ctx->rn, d0_bignum_size(ctx->rsa_n)));
365 CHECK(d0_bignum_mod_pow(temp0, ctx->rn, ctx->rsa_e, ctx->rsa_n));
366 CHECK(d0_bignum_mod_mul(temp1, ctx->schnorr_4_to_s, temp0, ctx->rsa_n));
367 CHECK(d0_iobuf_write_bignum(out, temp1));
368 return d0_iobuf_close(out, outbuflen);
371 d0_iobuf_close(out, outbuflen);
375 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)
380 // temps: temp0 temp1
381 USING(rsa_d); USING(rsa_n);
383 in = d0_iobuf_open_read(inbuf, inbuflen);
384 out = d0_iobuf_open_write(outbuf, *outbuflen);
386 CHECK(d0_iobuf_read_bignum(in, temp0));
387 CHECK(d0_bignum_mod_pow(temp1, temp0, ctx->rsa_d, ctx->rsa_n));
388 CHECK(d0_iobuf_write_bignum(out, temp1));
390 d0_iobuf_close(in, NULL);
391 return d0_iobuf_close(out, outbuflen);
394 d0_iobuf_close(in, NULL);
395 d0_iobuf_close(out, outbuflen);
399 WARN_UNUSED_RESULT BOOL d0_blind_id_finish_private_id_request(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
403 // temps: temp0 temp1
404 USING(rn); USING(rsa_n);
405 REPLACING(schnorr_4_to_s_signature);
407 in = d0_iobuf_open_read(inbuf, inbuflen);
409 CHECK(d0_iobuf_read_bignum(in, temp0));
410 CHECK(d0_bignum_mod_inv(temp1, ctx->rn, ctx->rsa_n));
411 CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_bignum_mod_mul(ctx->schnorr_4_to_s_signature, temp0, temp1, ctx->rsa_n));
413 return d0_iobuf_close(in, NULL);
416 d0_iobuf_close(in, NULL);
420 WARN_UNUSED_RESULT BOOL d0_blind_id_read_private_id(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
424 REPLACING(schnorr_s); REPLACING(schnorr_4_to_s); REPLACING(schnorr_4_to_s_signature);
426 in = d0_iobuf_open_read(inbuf, inbuflen);
428 CHECK_ASSIGN(ctx->schnorr_s, d0_iobuf_read_bignum(in, ctx->schnorr_s));
429 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s));
430 CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s_signature));
432 return d0_iobuf_close(in, NULL);
435 d0_iobuf_close(in, NULL);
439 WARN_UNUSED_RESULT BOOL d0_blind_id_read_public_id(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
443 REPLACING(schnorr_4_to_s); REPLACING(schnorr_4_to_s_signature);
445 in = d0_iobuf_open_read(inbuf, inbuflen);
447 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s));
448 CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s_signature));
450 return d0_iobuf_close(in, NULL);
453 d0_iobuf_close(in, NULL);
457 WARN_UNUSED_RESULT BOOL d0_blind_id_write_private_id(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
461 USING(schnorr_s); USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
463 out = d0_iobuf_open_write(outbuf, *outbuflen);
465 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_s));
466 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
467 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s_signature));
469 return d0_iobuf_close(out, outbuflen);
472 d0_iobuf_close(out, outbuflen);
476 WARN_UNUSED_RESULT BOOL d0_blind_id_write_public_id(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
480 USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
482 out = d0_iobuf_open_write(outbuf, *outbuflen);
484 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
485 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s_signature));
487 return d0_iobuf_close(out, outbuflen);
490 d0_iobuf_close(out, outbuflen);
494 WARN_UNUSED_RESULT BOOL d0_blind_id_authenticate_with_private_id_start(d0_blind_id_t *ctx, BOOL is_first, BOOL send_modulus, char *msg, size_t msglen, char *outbuf, size_t *outbuflen)
496 // first run: send 4^s, 4^s signature
497 // 1. get random r, send HASH(4^r)
500 unsigned char convbuf[1024];
506 USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
511 out = d0_iobuf_open_write(outbuf, *outbuflen);
517 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
518 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
519 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s_signature));
522 // start schnorr ID scheme
523 // generate random number r; x = g^r; send hash of x, remember r, forget x
524 CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
525 CHECK_ASSIGN(ctx->r, d0_bignum_rand_range(ctx->r, zero, temp0));
526 CHECK(d0_bignum_mod_pow(temp0, four, ctx->r, ctx->schnorr_G));
528 // hash it, hash it, everybody hash it
529 conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
530 CHECK(d0_iobuf_write_bignum(conv, temp0));
531 CHECK(d0_iobuf_write_packet(conv, msg, msglen));
532 CHECK(d0_iobuf_write_bignum(conv, temp0));
533 d0_iobuf_close(conv, &sz);
535 CHECK(d0_iobuf_write_raw(out, sha(convbuf, sz), SCHNORR_HASHSIZE) == SCHNORR_HASHSIZE);
536 CHECK(d0_iobuf_write_packet(out, msg, msglen));
538 return d0_iobuf_close(out, outbuflen);
541 d0_iobuf_close(out, outbuflen);
545 WARN_UNUSED_RESULT BOOL d0_blind_id_authenticate_with_private_id_challenge(d0_blind_id_t *ctx, BOOL is_first, BOOL recv_modulus, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen, BOOL *status)
546 // first run: get 4^s, 4^s signature
549 // 3. send challenge e of SCHNORR_BITS
556 REPLACING(schnorr_4_to_s); REPLACING(k); REPLACING(schnorr_4_to_s_signature);
563 USING(schnorr_4_to_s_signature); USING(schnorr_4_to_s);
566 USING(rsa_e); USING(rsa_n);
567 REPLACING(e); REPLACING(msg); REPLACING(msglen);
569 in = d0_iobuf_open_read(inbuf, inbuflen);
570 out = d0_iobuf_open_write(outbuf, *outbuflen);
576 CHECK_ASSIGN(ctx->schnorr_G, d0_iobuf_read_bignum(in, ctx->schnorr_G));
577 CHECK(d0_bignum_cmp(ctx->schnorr_G, zero) > 0);
578 CHECK(d0_bignum_cmp(ctx->schnorr_G, ctx->rsa_n) < 0);
580 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s));
581 CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s, zero) > 0);
582 CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s, ctx->schnorr_G) < 0);
583 CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s_signature));
584 CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s_signature, zero) >= 0);
585 CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s_signature, ctx->rsa_n) < 0);
587 // check signature of key (t = k^d, so, t^e = k)
588 CHECK(d0_bignum_mod_pow(temp0, ctx->schnorr_4_to_s_signature, ctx->rsa_e, ctx->rsa_n));
589 if(d0_bignum_cmp(temp0, ctx->schnorr_4_to_s))
591 // accept the key anyway, but mark as failed signature! will later return 0 in status
592 CHECK(d0_bignum_zero(ctx->schnorr_4_to_s_signature));
596 CHECK(d0_iobuf_read_raw(in, ctx->xnbh, SCHNORR_HASHSIZE));
597 ctx->msglen = MSGSIZE;
598 CHECK(d0_iobuf_read_packet(in, ctx->msg, &ctx->msglen));
601 CHECK_ASSIGN(ctx->e, d0_bignum_rand_bit_atmost(ctx->e, SCHNORR_BITS));
603 CHECK(d0_iobuf_write_bignum(out, ctx->e));
606 *status = !!d0_bignum_cmp(ctx->schnorr_4_to_s_signature, zero);
608 d0_iobuf_close(in, NULL);
609 return d0_iobuf_close(out, outbuflen);
612 d0_iobuf_close(in, NULL);
613 d0_iobuf_close(out, outbuflen);
617 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)
618 // 1. read challenge e of SCHNORR_BITS
619 // 2. reply with r + s * e mod order
624 // temps: 0 order, 1 prod, 2 y, 3 e
625 USING(schnorr_G); USING(schnorr_s); USING(r);
627 in = d0_iobuf_open_read(inbuf, inbuflen);
628 out = d0_iobuf_open_write(outbuf, *outbuflen);
630 CHECK(d0_iobuf_read_bignum(in, temp3));
631 // TODO check if >= 2^SCHNORR_BITS or < 0, if yes, then fail (needed for zero knowledge)
632 CHECK(d0_bignum_cmp(temp3, zero) >= 0);
633 CHECK(d0_bignum_size(temp3) <= SCHNORR_BITS);
635 // send response for schnorr ID scheme
636 // i.e. r + ctx->schnorr_s * temp3
637 CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
638 CHECK(d0_bignum_mod_mul(temp1, ctx->schnorr_s, temp3, temp0));
639 CHECK(d0_bignum_mod_add(temp2, temp1, ctx->r, temp0));
640 CHECK(d0_iobuf_write_bignum(out, temp2));
642 d0_iobuf_close(in, NULL);
643 return d0_iobuf_close(out, outbuflen);
646 d0_iobuf_close(in, NULL);
647 d0_iobuf_close(out, outbuflen);
651 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)
652 // 1. read y = r + s * e mod order
653 // 2. verify: g^y (g^s)^-e = g^(r+s*e-s*e) = g^r
654 // (check using H(g^r) which we know)
657 unsigned char convbuf[1024];
661 // temps: 0 y 1 order
662 USING(e); USING(schnorr_G);
664 in = d0_iobuf_open_read(inbuf, inbuflen);
667 CHECK(d0_dl_get_order(temp1, ctx->schnorr_G));
668 CHECK(d0_iobuf_read_bignum(in, temp0));
669 CHECK(d0_bignum_cmp(temp0, zero) >= 0);
670 CHECK(d0_bignum_cmp(temp0, temp1) < 0);
672 // verify schnorr ID scheme
673 // we need 4^temp0 (g^s)^-e
674 CHECK(d0_bignum_neg(temp1, ctx->e));
675 CHECK(d0_bignum_mod_pow(temp2, ctx->schnorr_4_to_s, temp1, ctx->schnorr_G));
676 CHECK(d0_bignum_mod_pow(temp1, four, temp0, ctx->schnorr_G));
677 CHECK(d0_bignum_mod_mul(temp3, temp1, temp2, ctx->schnorr_G));
678 // hash must be equal to xnbh
680 // hash it, hash it, everybody hash it
681 conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
682 CHECK(d0_iobuf_write_bignum(conv, temp3));
683 CHECK(d0_iobuf_write_packet(conv, ctx->msg, ctx->msglen));
684 CHECK(d0_iobuf_write_bignum(conv, temp3));
685 d0_iobuf_close(conv, &sz);
687 if(memcmp(sha(convbuf, sz), ctx->xnbh, SCHNORR_HASHSIZE))
689 // FAIL (not owned by player)
694 *status = !!d0_bignum_cmp(ctx->schnorr_4_to_s_signature, zero);
696 if(ctx->msglen <= (size_t) *msglen)
697 memcpy(msg, ctx->msg, ctx->msglen);
699 memcpy(msg, ctx->msg, *msglen);
700 *msglen = ctx->msglen;
702 d0_iobuf_close(in, NULL);
706 d0_iobuf_close(in, NULL);
710 WARN_UNUSED_RESULT BOOL d0_blind_id_fingerprint64_public_id(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
714 static unsigned char convbuf[1024];
717 USING(schnorr_4_to_s);
719 out = d0_iobuf_open_write(outbuf, *outbuflen);
720 conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
722 CHECK(d0_iobuf_write_bignum(conv, ctx->schnorr_4_to_s));
723 CHECK(d0_iobuf_close(conv, &sz));
726 n = (*outbuflen / 4) * 3;
727 if(n > SHA_DIGESTSIZE)
729 if(d0_iobuf_write_raw(out, sha(convbuf, sz), n) != n)
731 if(!d0_iobuf_conv_base64_out(out))
734 return d0_iobuf_close(out, outbuflen);
738 if(!d0_iobuf_close(conv, &sz)) { }
739 if(!d0_iobuf_close(out, outbuflen))
744 d0_blind_id_t *d0_blind_id_new(void)
746 d0_blind_id_t *b = d0_malloc(sizeof(d0_blind_id_t));
747 memset(b, 0, sizeof(*b));
751 void d0_blind_id_free(d0_blind_id_t *a)
753 d0_blind_id_clear(a);