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"
28 #define SHA_DIGESTSIZE 32
29 const char *sha(const char *in, size_t len)
32 d0_blind_id_util_sha256(h, in, len);
36 // for zero knowledge, we need multiple instances of schnorr ID scheme... should normally be sequential
37 // parallel schnorr ID is not provably zero knowledge :(
38 // (evil verifier can know all questions in advance, so sequential is disadvantage for him)
39 // we'll just live with a 1:1048576 chance of cheating, and support reauthenticating
41 #define SCHNORR_BITS 20
42 // probability of cheat: 2^(-bits+1)
44 #define SCHNORR_HASHSIZE SHA_DIGESTSIZE
45 // cannot be >= SHA_DIGESTSIZE
46 // *8 must be >= SCHNORR_BITS
47 // no need to save bits here
49 #define MSGSIZE 640 // ought to be enough for anyone
53 // signing (Xonotic pub and priv key)
54 d0_bignum_t *rsa_n, *rsa_e, *rsa_d;
56 // public data (Schnorr ID)
57 d0_bignum_t *schnorr_G;
59 // private data (player ID private key)
60 d0_bignum_t *schnorr_s;
62 // public data (player ID public key, this is what the server gets to know)
63 d0_bignum_t *schnorr_4_to_s;
64 d0_bignum_t *schnorr_H_4_to_s_signature; // 0 when signature is invalid
65 // as hash function H, we get the SHA1 and reinterpret as bignum - yes, it always is < 160 bits
68 d0_bignum_t *rsa_blind_signature_camouflage; // random number blind signature
70 d0_bignum_t *r; // random number for schnorr ID
71 d0_bignum_t *t; // for DH key exchange
72 d0_bignum_t *other_4_to_t; // for DH key exchange
73 d0_bignum_t *challenge; // challenge
75 char msghash[SCHNORR_HASHSIZE]; // init hash
76 char msg[MSGSIZE]; // message
77 size_t msglen; // message length
80 #define CHECK(x) do { if(!(x)) goto fail; } while(0)
81 #define CHECK_ASSIGN(var, value) do { d0_bignum_t *val; val = value; if(!val) goto fail; var = val; } while(0)
83 #define USING(x) if(!(ctx->x)) return 0
86 static d0_bignum_t *zero, *one, *four, *temp0, *temp1, *temp2, *temp3, *temp4;
88 void d0_blind_id_INITIALIZE(void)
90 d0_bignum_INITIALIZE();
91 CHECK_ASSIGN(zero, d0_bignum_int(zero, 0));
92 CHECK_ASSIGN(one, d0_bignum_int(one, 1));
93 CHECK_ASSIGN(four, d0_bignum_int(four, 4));
94 CHECK_ASSIGN(temp0, d0_bignum_int(temp0, 0));
95 CHECK_ASSIGN(temp1, d0_bignum_int(temp1, 0));
96 CHECK_ASSIGN(temp2, d0_bignum_int(temp2, 0));
97 CHECK_ASSIGN(temp3, d0_bignum_int(temp3, 0));
98 CHECK_ASSIGN(temp4, d0_bignum_int(temp4, 0));
103 void d0_blind_id_SHUTDOWN(void)
105 d0_bignum_free(zero);
107 d0_bignum_free(four);
108 d0_bignum_free(temp0);
109 d0_bignum_free(temp1);
110 d0_bignum_free(temp2);
111 d0_bignum_free(temp3);
112 d0_bignum_free(temp4);
113 d0_bignum_SHUTDOWN();
117 d0_bignum_t *d0_dl_get_order(d0_bignum_t *o, const d0_bignum_t *G)
119 CHECK_ASSIGN(o, d0_bignum_sub(o, G, one));
120 CHECK(d0_bignum_shl(o, o, -1)); // order o = (G-1)/2
126 d0_bignum_t *d0_dl_get_from_order(d0_bignum_t *G, const d0_bignum_t *o)
128 CHECK_ASSIGN(G, d0_bignum_shl(G, o, 1));
129 CHECK(d0_bignum_add(G, G, one));
135 BOOL d0_dl_generate_key(size_t size, d0_bignum_t *G)
142 CHECK(d0_bignum_rand_bit_exact(temp0, size-1));
143 if(d0_bignum_isprime(temp0, 0) == 0)
145 CHECK(d0_dl_get_from_order(G, temp0));
146 if(d0_bignum_isprime(G, 10) == 0)
148 if(d0_bignum_isprime(temp0, 10) == 0) // finish the previous test
157 BOOL d0_rsa_generate_key(size_t size, const d0_bignum_t *challenge, d0_bignum_t *d, d0_bignum_t *n)
159 // uses temp0 to temp4
162 int pb = (size + 1)/2;
170 CHECK(d0_bignum_rand_bit_exact(temp0, pb));
171 if(d0_bignum_isprime(temp0, 10) == 0)
173 CHECK(d0_bignum_sub(temp2, temp0, one));
174 CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp2, challenge));
175 if(!d0_bignum_cmp(temp4, one))
184 CHECK(d0_bignum_rand_bit_exact(temp1, qb));
185 if(!d0_bignum_cmp(temp1, temp0))
191 if(d0_bignum_isprime(temp1, 10) == 0)
193 CHECK(d0_bignum_sub(temp3, temp1, one));
194 CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp3, challenge));
195 if(!d0_bignum_cmp(temp4, one))
203 CHECK(d0_bignum_mul(n, temp0, temp1));
205 // d = challenge^-1 mod (temp0-1)(temp1-1)
206 CHECK(d0_bignum_mul(temp0, temp2, temp3));
207 CHECK(d0_bignum_mod_inv(d, challenge, temp0));
213 BOOL d0_rsa_generate_key_fastreject(size_t size, d0_fastreject_function reject, d0_blind_id_t *ctx, void *pass)
215 // uses temp0 to temp4
218 int pb = (size + 1)/2;
226 CHECK(d0_bignum_rand_bit_exact(temp0, pb));
227 if(d0_bignum_isprime(temp0, 10) == 0)
229 CHECK(d0_bignum_sub(temp2, temp0, one));
230 CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp2, ctx->rsa_e));
231 if(!d0_bignum_cmp(temp4, one))
240 CHECK(d0_bignum_rand_bit_exact(temp1, qb));
241 if(!d0_bignum_cmp(temp1, temp0))
249 CHECK(d0_bignum_mul(ctx->rsa_n, temp0, temp1));
250 if(reject(ctx, pass))
253 if(d0_bignum_isprime(temp1, 10) == 0)
255 CHECK(d0_bignum_sub(temp3, temp1, one));
256 CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp3, ctx->rsa_e));
257 if(!d0_bignum_cmp(temp4, one))
264 // ctx->rsa_d = ctx->rsa_e^-1 mod (temp0-1)(temp1-1)
265 CHECK(d0_bignum_mul(temp0, temp2, temp3));
266 CHECK(d0_bignum_mod_inv(ctx->rsa_d, ctx->rsa_e, temp0));
272 WARN_UNUSED_RESULT BOOL d0_longhash_destructive(d0_bignum_t *clobberme, char *outbuf, size_t outbuflen)
274 d0_iobuf_t *out = NULL;
275 static unsigned char convbuf[1024];
279 while(n > SHA_DIGESTSIZE)
281 sz = (d0_bignum_size(clobberme) + 7) / 8;
282 CHECK(d0_bignum_export_unsigned(clobberme, convbuf, sizeof(convbuf)) >= 0);
283 memcpy(outbuf, sha(convbuf, sz), SHA_DIGESTSIZE);
284 outbuf += SHA_DIGESTSIZE;
286 CHECK(d0_bignum_add(clobberme, clobberme, one));
288 sz = (d0_bignum_size(clobberme) + 7) / 8;
289 CHECK(d0_bignum_export_unsigned(clobberme, convbuf, sizeof(convbuf)) >= 0);
290 memcpy(outbuf, sha(convbuf, sz), n);
297 void d0_blind_id_clear(d0_blind_id_t *ctx)
299 if(ctx->rsa_n) d0_bignum_free(ctx->rsa_n);
300 if(ctx->rsa_e) d0_bignum_free(ctx->rsa_e);
301 if(ctx->rsa_d) d0_bignum_free(ctx->rsa_d);
302 if(ctx->schnorr_G) d0_bignum_free(ctx->schnorr_G);
303 if(ctx->schnorr_s) d0_bignum_free(ctx->schnorr_s);
304 if(ctx->schnorr_4_to_s) d0_bignum_free(ctx->schnorr_4_to_s);
305 if(ctx->schnorr_H_4_to_s_signature) d0_bignum_free(ctx->schnorr_H_4_to_s_signature);
306 if(ctx->rsa_blind_signature_camouflage) d0_bignum_free(ctx->rsa_blind_signature_camouflage);
307 if(ctx->r) d0_bignum_free(ctx->r);
308 if(ctx->challenge) d0_bignum_free(ctx->challenge);
309 if(ctx->t) d0_bignum_free(ctx->t);
310 if(ctx->other_4_to_t) d0_bignum_free(ctx->other_4_to_t);
311 memset(ctx, 0, sizeof(*ctx));
314 WARN_UNUSED_RESULT BOOL d0_blind_id_copy(d0_blind_id_t *ctx, const d0_blind_id_t *src)
316 d0_blind_id_clear(ctx);
317 if(src->rsa_n) CHECK_ASSIGN(ctx->rsa_n, d0_bignum_mov(NULL, src->rsa_n));
318 if(src->rsa_e) CHECK_ASSIGN(ctx->rsa_e, d0_bignum_mov(NULL, src->rsa_e));
319 if(src->rsa_d) CHECK_ASSIGN(ctx->rsa_d, d0_bignum_mov(NULL, src->rsa_d));
320 if(src->schnorr_G) CHECK_ASSIGN(ctx->schnorr_G, d0_bignum_mov(NULL, src->schnorr_G));
321 if(src->schnorr_s) CHECK_ASSIGN(ctx->schnorr_s, d0_bignum_mov(NULL, src->schnorr_s));
322 if(src->schnorr_4_to_s) CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_bignum_mov(NULL, src->schnorr_4_to_s));
323 if(src->schnorr_H_4_to_s_signature) CHECK_ASSIGN(ctx->schnorr_H_4_to_s_signature, d0_bignum_mov(NULL, src->schnorr_H_4_to_s_signature));
324 if(src->rsa_blind_signature_camouflage) CHECK_ASSIGN(ctx->rsa_blind_signature_camouflage, d0_bignum_mov(NULL, src->rsa_blind_signature_camouflage));
325 if(src->r) CHECK_ASSIGN(ctx->r, d0_bignum_mov(NULL, src->r));
326 if(src->challenge) CHECK_ASSIGN(ctx->challenge, d0_bignum_mov(NULL, src->challenge));
327 if(src->t) CHECK_ASSIGN(ctx->t, d0_bignum_mov(NULL, src->t));
328 if(src->other_4_to_t) CHECK_ASSIGN(ctx->other_4_to_t, d0_bignum_mov(NULL, src->other_4_to_t));
329 memcpy(ctx->msg, src->msg, sizeof(ctx->msg));
330 ctx->msglen = src->msglen;
331 memcpy(ctx->msghash, src->msghash, sizeof(ctx->msghash));
334 d0_blind_id_clear(ctx);
338 WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_key_fastreject(d0_blind_id_t *ctx, int k, d0_fastreject_function reject, void *pass)
340 REPLACING(rsa_e); REPLACING(rsa_d); REPLACING(rsa_n);
342 CHECK_ASSIGN(ctx->rsa_e, d0_bignum_int(ctx->rsa_e, 65537));
343 CHECK_ASSIGN(ctx->rsa_d, d0_bignum_zero(ctx->rsa_d));
344 CHECK_ASSIGN(ctx->rsa_n, d0_bignum_zero(ctx->rsa_n));
346 CHECK(d0_rsa_generate_key_fastreject(k+1, reject, ctx, pass)); // must fit G for sure
348 CHECK(d0_rsa_generate_key(k+1, ctx->rsa_e, ctx->rsa_d, ctx->rsa_n)); // must fit G for sure
354 WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_key(d0_blind_id_t *ctx, int k)
356 return d0_blind_id_generate_private_key_fastreject(ctx, k, NULL, NULL);
359 WARN_UNUSED_RESULT BOOL d0_blind_id_read_private_key(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
361 d0_iobuf_t *in = NULL;
363 REPLACING(rsa_n); REPLACING(rsa_e); REPLACING(rsa_d);
365 in = d0_iobuf_open_read(inbuf, inbuflen);
367 CHECK_ASSIGN(ctx->rsa_n, d0_iobuf_read_bignum(in, ctx->rsa_n));
368 CHECK_ASSIGN(ctx->rsa_e, d0_iobuf_read_bignum(in, ctx->rsa_e));
369 CHECK_ASSIGN(ctx->rsa_d, d0_iobuf_read_bignum(in, ctx->rsa_d));
370 return d0_iobuf_close(in, NULL);
373 d0_iobuf_close(in, NULL);
377 WARN_UNUSED_RESULT BOOL d0_blind_id_read_public_key(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
379 d0_iobuf_t *in = NULL;
381 REPLACING(rsa_n); REPLACING(rsa_e);
383 in = d0_iobuf_open_read(inbuf, inbuflen);
384 CHECK_ASSIGN(ctx->rsa_n, d0_iobuf_read_bignum(in, ctx->rsa_n));
385 CHECK_ASSIGN(ctx->rsa_e, d0_iobuf_read_bignum(in, ctx->rsa_e));
386 return d0_iobuf_close(in, NULL);
389 d0_iobuf_close(in, NULL);
393 WARN_UNUSED_RESULT BOOL d0_blind_id_write_private_key(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
395 d0_iobuf_t *out = NULL;
397 USING(rsa_n); USING(rsa_e); USING(rsa_d);
399 out = d0_iobuf_open_write(outbuf, *outbuflen);
400 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_n));
401 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_e));
402 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_d));
403 return d0_iobuf_close(out, outbuflen);
406 d0_iobuf_close(out, outbuflen);
410 WARN_UNUSED_RESULT BOOL d0_blind_id_write_public_key(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
412 d0_iobuf_t *out = NULL;
414 USING(rsa_n); USING(rsa_e);
416 out = d0_iobuf_open_write(outbuf, *outbuflen);
417 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_n));
418 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_e));
419 return d0_iobuf_close(out, outbuflen);
422 if(!d0_iobuf_close(out, outbuflen))
427 WARN_UNUSED_RESULT BOOL d0_blind_id_fingerprint64_public_key(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
429 d0_iobuf_t *out = NULL;
430 static unsigned char convbuf[2048];
431 d0_iobuf_t *conv = NULL;
434 USING(rsa_n); USING(rsa_e);
436 out = d0_iobuf_open_write(outbuf, *outbuflen);
437 conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
439 CHECK(d0_iobuf_write_bignum(conv, ctx->rsa_n));
440 CHECK(d0_iobuf_write_bignum(conv, ctx->rsa_e));
441 CHECK(d0_iobuf_close(conv, &sz));
444 n = (*outbuflen / 4) * 3;
445 if(n > SHA_DIGESTSIZE)
447 CHECK(d0_iobuf_write_raw(out, sha(convbuf, sz), n) == n);
448 CHECK(d0_iobuf_conv_base64_out(out));
450 return d0_iobuf_close(out, outbuflen);
454 d0_iobuf_close(conv, &sz);
455 d0_iobuf_close(out, outbuflen);
459 WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_id_modulus(d0_blind_id_t *ctx)
462 REPLACING(schnorr_G);
464 CHECK_ASSIGN(ctx->schnorr_G, d0_bignum_zero(ctx->schnorr_G));
465 CHECK(d0_dl_generate_key(d0_bignum_size(ctx->rsa_n)-1, ctx->schnorr_G));
471 WARN_UNUSED_RESULT BOOL d0_blind_id_read_private_id_modulus(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
473 d0_iobuf_t *in = NULL;
475 REPLACING(schnorr_G);
477 in = d0_iobuf_open_read(inbuf, inbuflen);
478 CHECK_ASSIGN(ctx->schnorr_G, d0_iobuf_read_bignum(in, ctx->schnorr_G));
479 return d0_iobuf_close(in, NULL);
482 d0_iobuf_close(in, NULL);
486 WARN_UNUSED_RESULT BOOL d0_blind_id_write_private_id_modulus(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
488 d0_iobuf_t *out = NULL;
492 out = d0_iobuf_open_write(outbuf, *outbuflen);
493 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
494 return d0_iobuf_close(out, outbuflen);
497 d0_iobuf_close(out, outbuflen);
501 WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_id_start(d0_blind_id_t *ctx)
503 // temps: temp0 = order
505 REPLACING(schnorr_s); REPLACING(schnorr_4_to_s);
507 CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
508 CHECK_ASSIGN(ctx->schnorr_s, d0_bignum_rand_range(ctx->schnorr_s, zero, temp0));
509 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_bignum_mod_pow(ctx->schnorr_4_to_s, four, ctx->schnorr_s, ctx->schnorr_G));
510 CHECK_ASSIGN(ctx->schnorr_H_4_to_s_signature, d0_bignum_zero(ctx->schnorr_H_4_to_s_signature));
517 WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_id_request(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
519 d0_iobuf_t *out = NULL;
520 static unsigned char convbuf[2048], shabuf[2048];
523 // temps: temp0 rsa_blind_signature_camouflage^challenge, temp1 (4^s)*rsa_blind_signature_camouflage^challenge
524 USING(rsa_n); USING(rsa_e); USING(schnorr_4_to_s);
525 REPLACING(rsa_blind_signature_camouflage);
527 out = d0_iobuf_open_write(outbuf, *outbuflen);
529 CHECK_ASSIGN(ctx->rsa_blind_signature_camouflage, d0_bignum_rand_bit_atmost(ctx->rsa_blind_signature_camouflage, d0_bignum_size(ctx->rsa_n)));
530 CHECK(d0_bignum_mod_pow(temp0, ctx->rsa_blind_signature_camouflage, ctx->rsa_e, ctx->rsa_n));
532 // we will actually sign HA(4^s) to prevent a malleability attack!
533 CHECK(d0_bignum_mov(temp2, ctx->schnorr_4_to_s));
534 sz = (d0_bignum_size(ctx->rsa_n) + 7) / 8; // this is too long, so we have to take the value % rsa_n when "decrypting"
535 if(sz > sizeof(shabuf))
537 CHECK(d0_longhash_destructive(temp2, shabuf, sz));
538 CHECK(d0_bignum_import_unsigned(temp2, shabuf, sz));
541 CHECK(d0_bignum_mod_mul(temp1, temp2, temp0, ctx->rsa_n));
542 CHECK(d0_iobuf_write_bignum(out, temp1));
543 return d0_iobuf_close(out, outbuflen);
546 d0_iobuf_close(out, outbuflen);
550 WARN_UNUSED_RESULT BOOL d0_blind_id_answer_private_id_request(const d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen)
552 d0_iobuf_t *in = NULL;
553 d0_iobuf_t *out = NULL;
555 // temps: temp0 input, temp1 temp0^d
556 USING(rsa_d); USING(rsa_n);
558 in = d0_iobuf_open_read(inbuf, inbuflen);
559 out = d0_iobuf_open_write(outbuf, *outbuflen);
561 CHECK(d0_iobuf_read_bignum(in, temp0));
562 CHECK(d0_bignum_mod_pow(temp1, temp0, ctx->rsa_d, ctx->rsa_n));
563 CHECK(d0_iobuf_write_bignum(out, temp1));
565 d0_iobuf_close(in, NULL);
566 return d0_iobuf_close(out, outbuflen);
569 d0_iobuf_close(in, NULL);
570 d0_iobuf_close(out, outbuflen);
574 WARN_UNUSED_RESULT BOOL d0_blind_id_finish_private_id_request(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
576 d0_iobuf_t *in = NULL;
578 // temps: temp0 input, temp1 rsa_blind_signature_camouflage^-1
579 USING(rsa_blind_signature_camouflage); USING(rsa_n);
580 REPLACING(schnorr_H_4_to_s_signature);
582 in = d0_iobuf_open_read(inbuf, inbuflen);
584 CHECK(d0_iobuf_read_bignum(in, temp0));
585 CHECK(d0_bignum_mod_inv(temp1, ctx->rsa_blind_signature_camouflage, ctx->rsa_n));
586 CHECK_ASSIGN(ctx->schnorr_H_4_to_s_signature, d0_bignum_mod_mul(ctx->schnorr_H_4_to_s_signature, temp0, temp1, ctx->rsa_n));
588 return d0_iobuf_close(in, NULL);
591 d0_iobuf_close(in, NULL);
595 WARN_UNUSED_RESULT BOOL d0_blind_id_read_private_id_request_camouflage(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
597 d0_iobuf_t *in = NULL;
599 REPLACING(rsa_blind_signature_camouflage);
601 in = d0_iobuf_open_read(inbuf, inbuflen);
603 CHECK_ASSIGN(ctx->rsa_blind_signature_camouflage, d0_iobuf_read_bignum(in, ctx->rsa_blind_signature_camouflage));
605 return d0_iobuf_close(in, NULL);
608 d0_iobuf_close(in, NULL);
612 WARN_UNUSED_RESULT BOOL d0_blind_id_write_private_id_request_camouflage(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
614 d0_iobuf_t *out = NULL;
616 USING(rsa_blind_signature_camouflage);
618 out = d0_iobuf_open_write(outbuf, *outbuflen);
620 CHECK(d0_iobuf_write_bignum(out, ctx->rsa_blind_signature_camouflage));
622 return d0_iobuf_close(out, outbuflen);
625 d0_iobuf_close(out, outbuflen);
629 WARN_UNUSED_RESULT BOOL d0_blind_id_read_private_id(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
631 d0_iobuf_t *in = NULL;
633 REPLACING(schnorr_s); REPLACING(schnorr_4_to_s); REPLACING(schnorr_H_4_to_s_signature);
635 in = d0_iobuf_open_read(inbuf, inbuflen);
637 CHECK_ASSIGN(ctx->schnorr_s, d0_iobuf_read_bignum(in, ctx->schnorr_s));
638 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s));
639 CHECK_ASSIGN(ctx->schnorr_H_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_H_4_to_s_signature));
641 return d0_iobuf_close(in, NULL);
644 d0_iobuf_close(in, NULL);
648 WARN_UNUSED_RESULT BOOL d0_blind_id_read_public_id(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
650 d0_iobuf_t *in = NULL;
652 REPLACING(schnorr_4_to_s); REPLACING(schnorr_H_4_to_s_signature);
654 in = d0_iobuf_open_read(inbuf, inbuflen);
656 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s));
657 CHECK_ASSIGN(ctx->schnorr_H_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_H_4_to_s_signature));
659 return d0_iobuf_close(in, NULL);
662 d0_iobuf_close(in, NULL);
666 WARN_UNUSED_RESULT BOOL d0_blind_id_write_private_id(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
668 d0_iobuf_t *out = NULL;
670 USING(schnorr_s); USING(schnorr_4_to_s); USING(schnorr_H_4_to_s_signature);
672 out = d0_iobuf_open_write(outbuf, *outbuflen);
674 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_s));
675 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
676 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_H_4_to_s_signature));
678 return d0_iobuf_close(out, outbuflen);
681 d0_iobuf_close(out, outbuflen);
685 WARN_UNUSED_RESULT BOOL d0_blind_id_write_public_id(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
687 d0_iobuf_t *out = NULL;
689 USING(schnorr_4_to_s); USING(schnorr_H_4_to_s_signature);
691 out = d0_iobuf_open_write(outbuf, *outbuflen);
693 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
694 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_H_4_to_s_signature));
696 return d0_iobuf_close(out, outbuflen);
699 d0_iobuf_close(out, outbuflen);
703 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)
705 // first run: send 4^s, 4^s signature
706 // 1. get random r, send HASH(4^r)
708 d0_iobuf_t *out = NULL;
709 static unsigned char convbuf[1024];
710 d0_iobuf_t *conv = NULL;
713 // temps: temp0 order, temp0 4^r
716 USING(schnorr_4_to_s); USING(schnorr_H_4_to_s_signature);
721 out = d0_iobuf_open_write(outbuf, *outbuflen);
727 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
728 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
729 CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_H_4_to_s_signature));
732 // start schnorr ID scheme
733 // generate random number r; x = g^r; send hash of x, remember r, forget x
734 CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
735 CHECK_ASSIGN(ctx->r, d0_bignum_rand_range(ctx->r, zero, temp0));
736 CHECK(d0_bignum_mod_pow(temp0, four, ctx->r, ctx->schnorr_G));
738 // hash it, hash it, everybody hash it
739 conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
740 CHECK(d0_iobuf_write_bignum(conv, temp0));
741 CHECK(d0_iobuf_write_packet(conv, msg, msglen));
742 CHECK(d0_iobuf_write_bignum(conv, temp0));
743 d0_iobuf_close(conv, &sz);
745 CHECK(d0_iobuf_write_raw(out, sha(convbuf, sz), SCHNORR_HASHSIZE) == SCHNORR_HASHSIZE);
746 CHECK(d0_iobuf_write_packet(out, msg, msglen));
748 return d0_iobuf_close(out, outbuflen);
751 d0_iobuf_close(out, outbuflen);
755 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)
756 // first run: get 4^s, 4^s signature
759 // 3. send challenge challenge of SCHNORR_BITS
761 d0_iobuf_t *in = NULL;
762 d0_iobuf_t *out = NULL;
763 static unsigned char shabuf[2048];
766 // temps: temp0 order, temp0 signature check
769 REPLACING(schnorr_4_to_s); REPLACING(schnorr_H_4_to_s_signature);
771 REPLACING(schnorr_G);
777 USING(schnorr_4_to_s); USING(schnorr_H_4_to_s_signature);
780 USING(rsa_e); USING(rsa_n);
781 REPLACING(challenge); REPLACING(msg); REPLACING(msglen); REPLACING(msghash); REPLACING(r); REPLACING(t);
783 in = d0_iobuf_open_read(inbuf, inbuflen);
784 out = d0_iobuf_open_write(outbuf, *outbuflen);
790 CHECK_ASSIGN(ctx->schnorr_G, d0_iobuf_read_bignum(in, ctx->schnorr_G));
791 CHECK(d0_bignum_cmp(ctx->schnorr_G, zero) > 0);
792 CHECK(d0_bignum_cmp(ctx->schnorr_G, ctx->rsa_n) < 0);
794 CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s));
795 CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s, zero) >= 0);
796 CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s, ctx->schnorr_G) < 0);
797 CHECK_ASSIGN(ctx->schnorr_H_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_H_4_to_s_signature));
798 CHECK(d0_bignum_cmp(ctx->schnorr_H_4_to_s_signature, zero) >= 0);
799 CHECK(d0_bignum_cmp(ctx->schnorr_H_4_to_s_signature, ctx->rsa_n) < 0);
801 // check signature of key (t = k^d, so, t^challenge = k)
802 CHECK(d0_bignum_mod_pow(temp0, ctx->schnorr_H_4_to_s_signature, ctx->rsa_e, ctx->rsa_n));
804 // we will actually sign SHA(4^s) to prevent a malleability attack!
805 CHECK(d0_bignum_mov(temp2, ctx->schnorr_4_to_s));
806 sz = (d0_bignum_size(ctx->rsa_n) + 7) / 8; // this is too long, so we have to take the value % rsa_n when "decrypting"
807 if(sz > sizeof(shabuf))
809 CHECK(d0_longhash_destructive(temp2, shabuf, sz));
810 CHECK(d0_bignum_import_unsigned(temp2, shabuf, sz));
812 // + 7 / 8 is too large, so let's mod it
813 CHECK(d0_bignum_divmod(NULL, temp1, temp2, ctx->rsa_n));
816 if(d0_bignum_cmp(temp0, temp1))
818 // accept the key anyway, but mark as failed signature! will later return 0 in status
819 CHECK(d0_bignum_zero(ctx->schnorr_H_4_to_s_signature));
823 CHECK(d0_iobuf_read_raw(in, ctx->msghash, SCHNORR_HASHSIZE));
824 ctx->msglen = MSGSIZE;
825 CHECK(d0_iobuf_read_packet(in, ctx->msg, &ctx->msglen));
828 CHECK_ASSIGN(ctx->challenge, d0_bignum_rand_bit_atmost(ctx->challenge, SCHNORR_BITS));
829 CHECK(d0_iobuf_write_bignum(out, ctx->challenge));
831 // Diffie Hellmann send
832 CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
833 CHECK_ASSIGN(ctx->t, d0_bignum_rand_range(ctx->t, zero, temp0));
834 CHECK(d0_bignum_mod_pow(temp0, four, ctx->t, ctx->schnorr_G));
835 CHECK(d0_iobuf_write_bignum(out, temp0));
838 *status = !!d0_bignum_cmp(ctx->schnorr_H_4_to_s_signature, zero);
840 d0_iobuf_close(in, NULL);
841 return d0_iobuf_close(out, outbuflen);
844 d0_iobuf_close(in, NULL);
845 d0_iobuf_close(out, outbuflen);
849 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)
850 // 1. read challenge challenge of SCHNORR_BITS
851 // 2. reply with r + s * challenge mod order
853 d0_iobuf_t *in = NULL;
854 d0_iobuf_t *out = NULL;
856 // temps: 0 order, 1 prod, 2 y, 3 challenge
857 REPLACING(other_4_to_t); REPLACING(t);
858 USING(schnorr_G); USING(schnorr_s); USING(r);
860 in = d0_iobuf_open_read(inbuf, inbuflen);
861 out = d0_iobuf_open_write(outbuf, *outbuflen);
863 CHECK(d0_iobuf_read_bignum(in, temp3));
864 CHECK(d0_bignum_cmp(temp3, zero) >= 0);
865 CHECK(d0_bignum_size(temp3) <= SCHNORR_BITS);
867 // send response for schnorr ID scheme
868 // i.challenge. r + ctx->schnorr_s * temp3
869 CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
870 CHECK(d0_bignum_mod_mul(temp1, ctx->schnorr_s, temp3, temp0));
871 CHECK(d0_bignum_mod_add(temp2, temp1, ctx->r, temp0));
872 CHECK(d0_iobuf_write_bignum(out, temp2));
874 // Diffie Hellmann recv
875 CHECK_ASSIGN(ctx->other_4_to_t, d0_iobuf_read_bignum(in, ctx->other_4_to_t));
876 CHECK(d0_bignum_cmp(ctx->other_4_to_t, zero) > 0);
877 CHECK(d0_bignum_cmp(ctx->other_4_to_t, ctx->schnorr_G) < 0);
878 // Diffie Hellmann send
879 CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
880 CHECK_ASSIGN(ctx->t, d0_bignum_rand_range(ctx->t, zero, temp0));
881 // modify DH key value! (add |G|-r)
882 CHECK(d0_bignum_add(temp1, ctx->t, temp0));
883 CHECK(d0_bignum_sub(temp2, temp1, ctx->r));
884 // can be undone by multiplying with 4^r in the end
885 // ensures the party of the DH key exchange is the same party as the one of
886 // the auth protocol (MITM who changes DH key exchange must break auth protocol)
887 // trick is that MITM has no knowledge about g^r at this point, as he only
888 // knows it in hashed form
889 CHECK(d0_bignum_mod_pow(temp0, four, temp2, ctx->schnorr_G));
890 CHECK(d0_iobuf_write_bignum(out, temp0));
892 d0_iobuf_close(in, NULL);
893 return d0_iobuf_close(out, outbuflen);
896 d0_iobuf_close(in, NULL);
897 d0_iobuf_close(out, outbuflen);
901 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, size_t *msglen, BOOL *status)
902 // 1. read y = r + s * challenge mod order
903 // 2. verify: g^y (g^s)^-challenge = g^(r+s*challenge-s*challenge) = g^r
904 // (check using H(g^r) which we know)
906 d0_iobuf_t *in = NULL;
907 static unsigned char convbuf[1024];
908 d0_iobuf_t *conv = NULL;
911 // temps: 0 y 1 order
912 USING(challenge); USING(schnorr_G);
913 REPLACING(other_4_to_t);
915 in = d0_iobuf_open_read(inbuf, inbuflen);
917 CHECK(d0_dl_get_order(temp1, ctx->schnorr_G));
918 CHECK(d0_iobuf_read_bignum(in, temp0));
919 CHECK(d0_bignum_cmp(temp0, zero) >= 0);
920 CHECK(d0_bignum_cmp(temp0, temp1) < 0);
922 // verify schnorr ID scheme
923 // we need 4^r = 4^temp0 (g^s)^-challenge
924 CHECK(d0_bignum_neg(temp1, ctx->challenge));
925 CHECK(d0_bignum_mod_pow(temp2, ctx->schnorr_4_to_s, temp1, ctx->schnorr_G));
926 CHECK(d0_bignum_mod_pow(temp1, four, temp0, ctx->schnorr_G));
927 CHECK_ASSIGN(temp3, d0_bignum_mod_mul(temp3, temp1, temp2, ctx->schnorr_G));
929 // Diffie Hellmann recv
930 CHECK_ASSIGN(ctx->other_4_to_t, d0_iobuf_read_bignum(in, ctx->other_4_to_t));
931 CHECK(d0_bignum_cmp(ctx->other_4_to_t, zero) > 0);
932 CHECK(d0_bignum_cmp(ctx->other_4_to_t, ctx->schnorr_G) < 0);
933 // recover DH key value!
934 CHECK(d0_bignum_mod_mul(ctx->other_4_to_t, ctx->other_4_to_t, temp3, ctx->schnorr_G));
936 // hash it, hash it, everybody hash it
937 conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
938 CHECK(d0_iobuf_write_bignum(conv, temp3));
939 CHECK(d0_iobuf_write_packet(conv, ctx->msg, ctx->msglen));
940 CHECK(d0_iobuf_write_bignum(conv, temp3));
941 d0_iobuf_close(conv, &sz);
943 if(memcmp(sha(convbuf, sz), ctx->msghash, SCHNORR_HASHSIZE))
945 // FAIL (not owned by player)
950 *status = !!d0_bignum_cmp(ctx->schnorr_H_4_to_s_signature, zero);
952 if(ctx->msglen <= *msglen)
953 memcpy(msg, ctx->msg, ctx->msglen);
955 memcpy(msg, ctx->msg, *msglen);
956 *msglen = ctx->msglen;
958 d0_iobuf_close(in, NULL);
962 d0_iobuf_close(in, NULL);
966 WARN_UNUSED_RESULT BOOL d0_blind_id_fingerprint64_public_id(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
968 d0_iobuf_t *out = NULL;
969 static unsigned char convbuf[1024];
970 d0_iobuf_t *conv = NULL;
973 USING(schnorr_4_to_s);
975 out = d0_iobuf_open_write(outbuf, *outbuflen);
976 conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
978 CHECK(d0_iobuf_write_bignum(conv, ctx->schnorr_4_to_s));
979 CHECK(d0_iobuf_close(conv, &sz));
982 n = (*outbuflen / 4) * 3;
983 if(n > SHA_DIGESTSIZE)
985 CHECK(d0_iobuf_write_raw(out, sha(convbuf, sz), n) == n);
986 CHECK(d0_iobuf_conv_base64_out(out));
988 return d0_iobuf_close(out, outbuflen);
992 d0_iobuf_close(conv, &sz);
993 d0_iobuf_close(out, outbuflen);
997 BOOL d0_blind_id_sessionkey_public_id(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
999 USING(t); USING(other_4_to_t); USING(schnorr_G);
1001 // temps: temp0 result
1002 CHECK(d0_bignum_mod_pow(temp0, ctx->other_4_to_t, ctx->t, ctx->schnorr_G));
1003 return d0_longhash_destructive(temp0, outbuf, *outbuflen);
1009 d0_blind_id_t *d0_blind_id_new(void)
1011 d0_blind_id_t *b = d0_malloc(sizeof(d0_blind_id_t));
1012 memset(b, 0, sizeof(*b));
1016 void d0_blind_id_free(d0_blind_id_t *a)
1018 d0_blind_id_clear(a);
1022 void d0_blind_id_util_sha256(char *out, const char *in, size_t n)
1025 SHA256_Init(&context);
1026 SHA256_Update(&context, (const unsigned char *) in, n);
1027 return SHA256_Final((unsigned char *) out, &context);