3 #include <openssl/crypto.h>
4 #include <openssl/sha.h>
5 #include <openssl/err.h>
10 * In the definition, (xa, xb, xc, xd) are Alice's (x1, x2, x3, x4) or
11 * Bob's (x3, x4, x1, x2). If you see what I mean.
16 char *name; /* Must be unique */
21 BIGNUM *gxc; /* Alice's g^{x3} or Bob's g^{x1} */
22 BIGNUM *gxd; /* Alice's g^{x4} or Bob's g^{x2} */
28 BIGNUM *secret; /* The shared secret */
30 BIGNUM *xa; /* Alice's x1 or Bob's x3 */
31 BIGNUM *xb; /* Alice's x2 or Bob's x4 */
32 BIGNUM *key; /* The calculated (shared) key */
35 static void JPAKE_ZKP_init(JPAKE_ZKP *zkp)
41 static void JPAKE_ZKP_release(JPAKE_ZKP *zkp)
47 /* Two birds with one stone - make the global name as expected */
48 #define JPAKE_STEP_PART_init JPAKE_STEP2_init
49 #define JPAKE_STEP_PART_release JPAKE_STEP2_release
51 void JPAKE_STEP_PART_init(JPAKE_STEP_PART *p)
54 JPAKE_ZKP_init(&p->zkpx);
57 void JPAKE_STEP_PART_release(JPAKE_STEP_PART *p)
59 JPAKE_ZKP_release(&p->zkpx);
63 void JPAKE_STEP1_init(JPAKE_STEP1 *s1)
65 JPAKE_STEP_PART_init(&s1->p1);
66 JPAKE_STEP_PART_init(&s1->p2);
69 void JPAKE_STEP1_release(JPAKE_STEP1 *s1)
71 JPAKE_STEP_PART_release(&s1->p2);
72 JPAKE_STEP_PART_release(&s1->p1);
75 static void JPAKE_CTX_init(JPAKE_CTX *ctx, const char *name,
76 const char *peer_name, const BIGNUM *p,
77 const BIGNUM *g, const BIGNUM *q,
80 ctx->p.name = OPENSSL_strdup(name);
81 ctx->p.peer_name = OPENSSL_strdup(peer_name);
85 ctx->secret = BN_dup(secret);
87 ctx->p.gxc = BN_new();
88 ctx->p.gxd = BN_new();
93 ctx->ctx = BN_CTX_new();
96 static void JPAKE_CTX_release(JPAKE_CTX *ctx)
98 BN_CTX_free(ctx->ctx);
99 BN_clear_free(ctx->key);
100 BN_clear_free(ctx->xb);
101 BN_clear_free(ctx->xa);
106 BN_clear_free(ctx->secret);
110 OPENSSL_free(ctx->p.peer_name);
111 OPENSSL_free(ctx->p.name);
113 memset(ctx, '\0', sizeof *ctx);
116 JPAKE_CTX *JPAKE_CTX_new(const char *name, const char *peer_name,
117 const BIGNUM *p, const BIGNUM *g, const BIGNUM *q,
118 const BIGNUM *secret)
120 JPAKE_CTX *ctx = OPENSSL_malloc(sizeof *ctx);
122 JPAKE_CTX_init(ctx, name, peer_name, p, g, q, secret);
127 void JPAKE_CTX_free(JPAKE_CTX *ctx)
129 JPAKE_CTX_release(ctx);
133 static void hashlength(SHA_CTX *sha, size_t l)
137 OPENSSL_assert(l <= 0xffff);
140 SHA1_Update(sha, b, 2);
143 static void hashstring(SHA_CTX *sha, const char *string)
145 size_t l = strlen(string);
148 SHA1_Update(sha, string, l);
151 static void hashbn(SHA_CTX *sha, const BIGNUM *bn)
153 size_t l = BN_num_bytes(bn);
154 unsigned char *bin = OPENSSL_malloc(l);
158 SHA1_Update(sha, bin, l);
162 /* h=hash(g, g^r, g^x, name) */
163 static void zkp_hash(BIGNUM *h, const BIGNUM *zkpg, const JPAKE_STEP_PART *p,
164 const char *proof_name)
166 unsigned char md[SHA_DIGEST_LENGTH];
170 * XXX: hash should not allow moving of the boundaries - Java code
171 * is flawed in this respect. Length encoding seems simplest.
175 OPENSSL_assert(!BN_is_zero(p->zkpx.gr));
176 hashbn(&sha, p->zkpx.gr);
178 hashstring(&sha, proof_name);
179 SHA1_Final(md, &sha);
180 BN_bin2bn(md, SHA_DIGEST_LENGTH, h);
184 * Prove knowledge of x
185 * Note that p->gx has already been calculated
187 static void generate_zkp(JPAKE_STEP_PART *p, const BIGNUM *x,
188 const BIGNUM *zkpg, JPAKE_CTX *ctx)
190 BIGNUM *r = BN_new();
191 BIGNUM *h = BN_new();
192 BIGNUM *t = BN_new();
196 * XXX: Java chooses r in [0, 2^160) - i.e. distribution not uniform
198 BN_rand_range(r, ctx->p.q);
200 BN_mod_exp(p->zkpx.gr, zkpg, r, ctx->p.p, ctx->ctx);
203 zkp_hash(h, zkpg, p, ctx->p.name);
206 BN_mod_mul(t, x, h, ctx->p.q, ctx->ctx);
207 BN_mod_sub(p->zkpx.b, r, t, ctx->p.q, ctx->ctx);
215 static int verify_zkp(const JPAKE_STEP_PART *p, const BIGNUM *zkpg,
218 BIGNUM *h = BN_new();
219 BIGNUM *t1 = BN_new();
220 BIGNUM *t2 = BN_new();
221 BIGNUM *t3 = BN_new();
224 zkp_hash(h, zkpg, p, ctx->p.peer_name);
227 BN_mod_exp(t1, zkpg, p->zkpx.b, ctx->p.p, ctx->ctx);
228 /* t2 = (g^x)^h = g^{hx} */
229 BN_mod_exp(t2, p->gx, h, ctx->p.p, ctx->ctx);
230 /* t3 = t1 * t2 = g^{hx} * g^b = g^{hx+b} = g^r (allegedly) */
231 BN_mod_mul(t3, t1, t2, ctx->p.p, ctx->ctx);
233 /* verify t3 == g^r */
234 if(BN_cmp(t3, p->zkpx.gr) == 0)
237 JPAKEerr(JPAKE_F_VERIFY_ZKP, JPAKE_R_ZKP_VERIFY_FAILED);
248 static void generate_step_part(JPAKE_STEP_PART *p, const BIGNUM *x,
249 const BIGNUM *g, JPAKE_CTX *ctx)
251 BN_mod_exp(p->gx, g, x, ctx->p.p, ctx->ctx);
252 generate_zkp(p, x, g, ctx);
255 /* Generate each party's random numbers. xa is in [0, q), xb is in [1, q). */
256 static void genrand(JPAKE_CTX *ctx)
261 BN_rand_range(ctx->xa, ctx->p.q);
265 BN_copy(qm1, ctx->p.q);
268 /* ... and xb in [0, q-1) */
269 BN_rand_range(ctx->xb, qm1);
271 BN_add_word(ctx->xb, 1);
277 int JPAKE_STEP1_generate(JPAKE_STEP1 *send, JPAKE_CTX *ctx)
280 generate_step_part(&send->p1, ctx->xa, ctx->p.g, ctx);
281 generate_step_part(&send->p2, ctx->xb, ctx->p.g, ctx);
286 /* g^x is a legal value */
287 static int is_legal(const BIGNUM *gx, const JPAKE_CTX *ctx)
292 if(BN_is_negative(gx) || BN_is_zero(gx) || BN_cmp(gx, ctx->p.p) >= 0)
296 BN_mod_exp(t, gx, ctx->p.q, ctx->p.p, ctx->ctx);
303 int JPAKE_STEP1_process(JPAKE_CTX *ctx, const JPAKE_STEP1 *received)
305 if(!is_legal(received->p1.gx, ctx))
307 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X3_IS_NOT_LEGAL);
311 if(!is_legal(received->p2.gx, ctx))
313 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X4_IS_NOT_LEGAL);
317 /* verify their ZKP(xc) */
318 if(!verify_zkp(&received->p1, ctx->p.g, ctx))
320 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X3_FAILED);
324 /* verify their ZKP(xd) */
325 if(!verify_zkp(&received->p2, ctx->p.g, ctx))
327 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X4_FAILED);
332 if(BN_is_one(received->p2.gx))
334 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X4_IS_ONE);
338 /* Save the bits we need for later */
339 BN_copy(ctx->p.gxc, received->p1.gx);
340 BN_copy(ctx->p.gxd, received->p2.gx);
346 int JPAKE_STEP2_generate(JPAKE_STEP2 *send, JPAKE_CTX *ctx)
348 BIGNUM *t1 = BN_new();
349 BIGNUM *t2 = BN_new();
352 * X = g^{(xa + xc + xd) * xb * s}
355 BN_mod_exp(t1, ctx->p.g, ctx->xa, ctx->p.p, ctx->ctx);
356 /* t2 = t1 * g^{xc} = g^{xa} * g^{xc} = g^{xa + xc} */
357 BN_mod_mul(t2, t1, ctx->p.gxc, ctx->p.p, ctx->ctx);
358 /* t1 = t2 * g^{xd} = g^{xa + xc + xd} */
359 BN_mod_mul(t1, t2, ctx->p.gxd, ctx->p.p, ctx->ctx);
361 BN_mod_mul(t2, ctx->xb, ctx->secret, ctx->p.q, ctx->ctx);
365 * XXX: this is kinda funky, because we're using
367 * g' = g^{xa + xc + xd}
369 * as the generator, which means X is g'^{xb * s}
370 * X = t1^{t2} = t1^{xb * s} = g^{(xa + xc + xd) * xb * s}
372 generate_step_part(send, t2, t1, ctx);
381 /* gx = g^{xc + xa + xb} * xd * s */
382 static int compute_key(JPAKE_CTX *ctx, const BIGNUM *gx)
384 BIGNUM *t1 = BN_new();
385 BIGNUM *t2 = BN_new();
386 BIGNUM *t3 = BN_new();
389 * K = (gx/g^{xb * xd * s})^{xb}
390 * = (g^{(xc + xa + xb) * xd * s - xb * xd *s})^{xb}
391 * = (g^{(xa + xc) * xd * s})^{xb}
392 * = g^{(xa + xc) * xb * xd * s}
393 * [which is the same regardless of who calculates it]
396 /* t1 = (g^{xd})^{xb} = g^{xb * xd} */
397 BN_mod_exp(t1, ctx->p.gxd, ctx->xb, ctx->p.p, ctx->ctx);
399 BN_sub(t2, ctx->p.q, ctx->secret);
400 /* t3 = t1^t2 = g^{-xb * xd * s} */
401 BN_mod_exp(t3, t1, t2, ctx->p.p, ctx->ctx);
402 /* t1 = gx * t3 = X/g^{xb * xd * s} */
403 BN_mod_mul(t1, gx, t3, ctx->p.p, ctx->ctx);
405 BN_mod_exp(ctx->key, t1, ctx->xb, ctx->p.p, ctx->ctx);
415 int JPAKE_STEP2_process(JPAKE_CTX *ctx, const JPAKE_STEP2 *received)
417 BIGNUM *t1 = BN_new();
418 BIGNUM *t2 = BN_new();
422 * g' = g^{xc + xa + xb} [from our POV]
425 BN_mod_add(t1, ctx->xa, ctx->xb, ctx->p.q, ctx->ctx);
426 /* t2 = g^{t1} = g^{xa+xb} */
427 BN_mod_exp(t2, ctx->p.g, t1, ctx->p.p, ctx->ctx);
428 /* t1 = g^{xc} * t2 = g^{xc + xa + xb} */
429 BN_mod_mul(t1, ctx->p.gxc, t2, ctx->p.p, ctx->ctx);
431 if(verify_zkp(received, t1, ctx))
434 JPAKEerr(JPAKE_F_JPAKE_STEP2_PROCESS, JPAKE_R_VERIFY_B_FAILED);
436 compute_key(ctx, received->gx);
445 static void quickhashbn(unsigned char *md, const BIGNUM *bn)
451 SHA1_Final(md, &sha);
454 void JPAKE_STEP3A_init(JPAKE_STEP3A *s3a)
457 int JPAKE_STEP3A_generate(JPAKE_STEP3A *send, JPAKE_CTX *ctx)
459 quickhashbn(send->hhk, ctx->key);
460 SHA1(send->hhk, sizeof send->hhk, send->hhk);
465 int JPAKE_STEP3A_process(JPAKE_CTX *ctx, const JPAKE_STEP3A *received)
467 unsigned char hhk[SHA_DIGEST_LENGTH];
469 quickhashbn(hhk, ctx->key);
470 SHA1(hhk, sizeof hhk, hhk);
471 if(memcmp(hhk, received->hhk, sizeof hhk))
473 JPAKEerr(JPAKE_F_JPAKE_STEP3A_PROCESS, JPAKE_R_HASH_OF_HASH_OF_KEY_MISMATCH);
479 void JPAKE_STEP3A_release(JPAKE_STEP3A *s3a)
482 void JPAKE_STEP3B_init(JPAKE_STEP3B *s3b)
485 int JPAKE_STEP3B_generate(JPAKE_STEP3B *send, JPAKE_CTX *ctx)
487 quickhashbn(send->hk, ctx->key);
492 int JPAKE_STEP3B_process(JPAKE_CTX *ctx, const JPAKE_STEP3B *received)
494 unsigned char hk[SHA_DIGEST_LENGTH];
496 quickhashbn(hk, ctx->key);
497 if(memcmp(hk, received->hk, sizeof hk))
499 JPAKEerr(JPAKE_F_JPAKE_STEP3B_PROCESS, JPAKE_R_HASH_OF_KEY_MISMATCH);
505 void JPAKE_STEP3B_release(JPAKE_STEP3B *s3b)
508 const BIGNUM *JPAKE_get_shared_key(JPAKE_CTX *ctx)