diff options
author | Ben Laurie <ben@openssl.org> | 2008-10-26 18:42:05 +0000 |
---|---|---|
committer | Ben Laurie <ben@openssl.org> | 2008-10-26 18:42:05 +0000 |
commit | 2124e869a8da94e0540d44df15bbf6007da3bf91 (patch) | |
tree | 62394b46b1fb0360d4285323abf5a48dad36ce36 /crypto/jpake/jpake.c | |
parent | 3b668eedda78fcf712198b3d7c433a67989da407 (diff) |
Add JPAKE.
Diffstat (limited to 'crypto/jpake/jpake.c')
-rw-r--r-- | crypto/jpake/jpake.c | 468 |
1 files changed, 468 insertions, 0 deletions
diff --git a/crypto/jpake/jpake.c b/crypto/jpake/jpake.c new file mode 100644 index 0000000000..3ed1d1b158 --- /dev/null +++ b/crypto/jpake/jpake.c @@ -0,0 +1,468 @@ +#include "jpake.h" + +#include <openssl/crypto.h> +#include <openssl/sha.h> +#include <openssl/err.h> +#include <memory.h> +#include <assert.h> + +/* + * In the definition, (xa, xb, xc, xd) are Alice's (x1, x2, x3, x4) or + * Bob's (x3, x4, x1, x2). If you see what I mean. + */ + +typedef struct + { + char *name; // Must be unique + char *peer_name; + BIGNUM *p; + BIGNUM *g; + BIGNUM *q; + BIGNUM *gxc; // Alice's g^{x3} or Bob's g^{x1} + BIGNUM *gxd; // Alice's g^{x4} or Bob's g^{x2} + } JPAKE_CTX_PUBLIC; + +struct JPAKE_CTX + { + JPAKE_CTX_PUBLIC p; + BIGNUM *secret; // The shared secret + BN_CTX *ctx; + BIGNUM *xa; // Alice's x1 or Bob's x3 + BIGNUM *xb; // Alice's x2 or Bob's x4 + BIGNUM *key; // The calculated (shared) key + }; + +static void JPAKE_ZKP_init(JPAKE_ZKP *zkp) + { + zkp->gr = BN_new(); + zkp->b = BN_new(); + } + +static void JPAKE_ZKP_release(JPAKE_ZKP *zkp) + { + BN_free(zkp->b); + BN_free(zkp->gr); + } + +// Two birds with one stone - make the global name as expected +#define JPAKE_STEP_PART_init JPAKE_STEP2_init +#define JPAKE_STEP_PART_release JPAKE_STEP2_release + +void JPAKE_STEP_PART_init(JPAKE_STEP_PART *p) + { + p->gx = BN_new(); + JPAKE_ZKP_init(&p->zkpx); + } + +void JPAKE_STEP_PART_release(JPAKE_STEP_PART *p) + { + JPAKE_ZKP_release(&p->zkpx); + BN_free(p->gx); + } + +void JPAKE_STEP1_init(JPAKE_STEP1 *s1) + { + JPAKE_STEP_PART_init(&s1->p1); + JPAKE_STEP_PART_init(&s1->p2); + } + +void JPAKE_STEP1_release(JPAKE_STEP1 *s1) + { + JPAKE_STEP_PART_release(&s1->p2); + JPAKE_STEP_PART_release(&s1->p1); + } + +static void JPAKE_CTX_init(JPAKE_CTX *ctx, const char *name, + const char *peer_name, const BIGNUM *p, + const BIGNUM *g, const BIGNUM *q, + const BIGNUM *secret) + { + ctx->p.name = OPENSSL_strdup(name); + ctx->p.peer_name = OPENSSL_strdup(peer_name); + ctx->p.p = BN_dup(p); + ctx->p.g = BN_dup(g); + ctx->p.q = BN_dup(q); + ctx->secret = BN_dup(secret); + + ctx->p.gxc = BN_new(); + ctx->p.gxd = BN_new(); + + ctx->xa = BN_new(); + ctx->xb = BN_new(); + ctx->key = BN_new(); + ctx->ctx = BN_CTX_new(); + } + +static void JPAKE_CTX_release(JPAKE_CTX *ctx) + { + BN_CTX_free(ctx->ctx); + BN_clear_free(ctx->key); + BN_clear_free(ctx->xb); + BN_clear_free(ctx->xa); + + BN_free(ctx->p.gxd); + BN_free(ctx->p.gxc); + + BN_clear_free(ctx->secret); + BN_free(ctx->p.q); + BN_free(ctx->p.g); + BN_free(ctx->p.p); + OPENSSL_free(ctx->p.peer_name); + OPENSSL_free(ctx->p.name); + + memset(ctx, '\0', sizeof *ctx); + } + +JPAKE_CTX *JPAKE_CTX_new(const char *name, const char *peer_name, + const BIGNUM *p, const BIGNUM *g, const BIGNUM *q, + const BIGNUM *secret) + { + JPAKE_CTX *ctx = OPENSSL_malloc(sizeof *ctx); + + JPAKE_CTX_init(ctx, name, peer_name, p, g, q, secret); + + return ctx; + } + +void JPAKE_CTX_free(JPAKE_CTX *ctx) + { + JPAKE_CTX_release(ctx); + OPENSSL_free(ctx); + } + +static void hashlength(SHA_CTX *sha, size_t l) + { + unsigned char b[2]; + + assert(l <= 0xffff); + b[0] = l >> 8; + b[1] = l&0xff; + SHA1_Update(sha, b, 2); + } + +static void hashstring(SHA_CTX *sha, const char *string) + { + size_t l = strlen(string); + + hashlength(sha, l); + SHA1_Update(sha, string, l); + } + +static void hashbn(SHA_CTX *sha, const BIGNUM *bn) + { + size_t l = BN_num_bytes(bn); + unsigned char *bin = alloca(l); + + hashlength(sha, l); + BN_bn2bin(bn, bin); + SHA1_Update(sha, bin, l); + } + +// h=hash(g, g^r, g^x, name) +static void zkp_hash(BIGNUM *h, const BIGNUM *zkpg, const JPAKE_STEP_PART *p, + const char *proof_name) + { + unsigned char md[SHA_DIGEST_LENGTH]; + SHA_CTX sha; + + // XXX: hash should not allow moving of the boundaries - Java code + // is flawed in this respect. Length encoding seems simplest. + SHA1_Init(&sha); + hashbn(&sha, zkpg); + assert(!BN_is_zero(p->zkpx.gr)); + hashbn(&sha, p->zkpx.gr); + hashbn(&sha, p->gx); + hashstring(&sha, proof_name); + SHA1_Final(md, &sha); + BN_bin2bn(md, SHA_DIGEST_LENGTH, h); + } + +// Prove knowledge of x +// Note that p->gx has already been calculated +static void generate_zkp(JPAKE_STEP_PART *p, const BIGNUM *x, + const BIGNUM *zkpg, JPAKE_CTX *ctx) + { + BIGNUM *r = BN_new(); + BIGNUM *h = BN_new(); + BIGNUM *t = BN_new(); + + // r in [0,q) + // XXX: Java chooses r in [0, 2^160) - i.e. distribution not uniform + BN_rand_range(r, ctx->p.q); + // g^r + BN_mod_exp(p->zkpx.gr, zkpg, r, ctx->p.p, ctx->ctx); + + // h=hash... + zkp_hash(h, zkpg, p, ctx->p.name); + + // b = r - x*h + BN_mod_mul(t, x, h, ctx->p.q, ctx->ctx); + BN_mod_sub(p->zkpx.b, r, t, ctx->p.q, ctx->ctx); + + // cleanup + BN_free(t); + BN_free(h); + BN_free(r); + } + +static int verify_zkp(const JPAKE_STEP_PART *p, const BIGNUM *zkpg, + JPAKE_CTX *ctx) + { + BIGNUM *h = BN_new(); + BIGNUM *t1 = BN_new(); + BIGNUM *t2 = BN_new(); + BIGNUM *t3 = BN_new(); + int ret = 0; + + zkp_hash(h, zkpg, p, ctx->p.peer_name); + + // t1 = g^b + BN_mod_exp(t1, zkpg, p->zkpx.b, ctx->p.p, ctx->ctx); + // t2 = (g^x)^h = g^{hx} + BN_mod_exp(t2, p->gx, h, ctx->p.p, ctx->ctx); + // t3 = t1 * t2 = g^{hx} * g^b = g^{hx+b} = g^r (allegedly) + BN_mod_mul(t3, t1, t2, ctx->p.p, ctx->ctx); + + // verify t3 == g^r + if(BN_cmp(t3, p->zkpx.gr) == 0) + ret = 1; + else + JPAKEerr(JPAKE_F_VERIFY_ZKP, JPAKE_R_ZKP_VERIFY_FAILED); + + // cleanup + BN_free(t3); + BN_free(t2); + BN_free(t1); + BN_free(h); + + return ret; + } + +static void generate_step_part(JPAKE_STEP_PART *p, const BIGNUM *x, + const BIGNUM *g, JPAKE_CTX *ctx) + { + BN_mod_exp(p->gx, g, x, ctx->p.p, ctx->ctx); + generate_zkp(p, x, g, ctx); + } + +// Generate each party's random numbers. xa is in [0, q), xb is in [1, q). +static void genrand(JPAKE_CTX *ctx) + { + BIGNUM *qm1; + + // xa in [0, q) + BN_rand_range(ctx->xa, ctx->p.q); + + // q-1 + qm1 = BN_new(); + BN_copy(qm1, ctx->p.q); + BN_sub_word(qm1, 1); + + // ... and xb in [0, q-1) + BN_rand_range(ctx->xb, qm1); + // [1, q) + BN_add_word(ctx->xb, 1); + + // cleanup + BN_free(qm1); + } + +int JPAKE_STEP1_generate(JPAKE_STEP1 *send, JPAKE_CTX *ctx) + { + genrand(ctx); + generate_step_part(&send->p1, ctx->xa, ctx->p.g, ctx); + generate_step_part(&send->p2, ctx->xb, ctx->p.g, ctx); + + return 1; + } + +int JPAKE_STEP1_process(JPAKE_CTX *ctx, const JPAKE_STEP1 *received) + { + // verify their ZKP(xc) + if(!verify_zkp(&received->p1, ctx->p.g, ctx)) + { + JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X3_FAILED); + return 0; + } + + // verify their ZKP(xd) + if(!verify_zkp(&received->p2, ctx->p.g, ctx)) + { + JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X4_FAILED); + return 0; + } + + // g^xd != 1 + if(BN_is_one(received->p2.gx)) + { + JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X4_IS_ONE); + return 0; + } + + // Save the bits we need for later + BN_copy(ctx->p.gxc, received->p1.gx); + BN_copy(ctx->p.gxd, received->p2.gx); + + return 1; + } + + +int JPAKE_STEP2_generate(JPAKE_STEP2 *send, JPAKE_CTX *ctx) + { + BIGNUM *t1 = BN_new(); + BIGNUM *t2 = BN_new(); + + // X = g^{(xa + xc + xd) * xb * s} + // t1 = g^xa + BN_mod_exp(t1, ctx->p.g, ctx->xa, ctx->p.p, ctx->ctx); + // t2 = t1 * g^{xc} = g^{xa} * g^{xc} = g^{xa + xc} + BN_mod_mul(t2, t1, ctx->p.gxc, ctx->p.p, ctx->ctx); + // t1 = t2 * g^{xd} = g^{xa + xc + xd} + BN_mod_mul(t1, t2, ctx->p.gxd, ctx->p.p, ctx->ctx); + // t2 = xb * s + BN_mod_mul(t2, ctx->xb, ctx->secret, ctx->p.q, ctx->ctx); + + // ZKP(xb * s) + // XXX: this is kinda funky, because we're using + // + // g' = g^{xa + xc + xd} + // + // as the generator, which means X is g'^{xb * s} + // X = t1^{t2} = t1^{xb * s} = g^{(xa + xc + xd) * xb * s} + generate_step_part(send, t2, t1, ctx); + + // cleanup + BN_free(t1); + BN_free(t2); + + return 1; + } + +// gx = g^{xc + xa + xb} * xd * s +static int compute_key(JPAKE_CTX *ctx, const BIGNUM *gx) + { + BIGNUM *t1 = BN_new(); + BIGNUM *t2 = BN_new(); + BIGNUM *t3 = BN_new(); + + // K = (gx/g^{xb * xd * s})^{xb} + // = (g^{(xc + xa + xb) * xd * s - xb * xd *s})^{xb} + // = (g^{(xa + xc) * xd * s})^{xb} + // = g^{(xa + xc) * xb * xd * s} + // [which is the same regardless of who calculates it] + + // t1 = (g^{xd})^{xb} = g^{xb * xd} + BN_mod_exp(t1, ctx->p.gxd, ctx->xb, ctx->p.p, ctx->ctx); + // t2 = -s = q-s + BN_sub(t2, ctx->p.q, ctx->secret); + // t3 = t1^t2 = g^{-xb * xd * s} + BN_mod_exp(t3, t1, t2, ctx->p.p, ctx->ctx); + // t1 = gx * t3 = X/g^{xb * xd * s} + BN_mod_mul(t1, gx, t3, ctx->p.p, ctx->ctx); + // K = t1^{xb} + BN_mod_exp(ctx->key, t1, ctx->xb, ctx->p.p, ctx->ctx); + + // cleanup + BN_free(t3); + BN_free(t2); + BN_free(t1); + + return 1; + } + +int JPAKE_STEP2_process(JPAKE_CTX *ctx, const JPAKE_STEP2 *received) + { + BIGNUM *t1 = BN_new(); + BIGNUM *t2 = BN_new(); + int ret = 0; + + // g' = g^{xc + xa + xb} [from our POV] + // t1 = xa + xb + BN_mod_add(t1, ctx->xa, ctx->xb, ctx->p.q, ctx->ctx); + // t2 = g^{t1} = g^{xa+xb} + BN_mod_exp(t2, ctx->p.g, t1, ctx->p.p, ctx->ctx); + // t1 = g^{xc} * t2 = g^{xc + xa + xb} + BN_mod_mul(t1, ctx->p.gxc, t2, ctx->p.p, ctx->ctx); + + if(verify_zkp(received, t1, ctx)) + ret = 1; + else + JPAKEerr(JPAKE_F_JPAKE_STEP2_PROCESS, JPAKE_R_VERIFY_B_FAILED); + + compute_key(ctx, received->gx); + + // cleanup + BN_free(t2); + BN_free(t1); + + return ret; + } + +static void quickhashbn(unsigned char *md, const BIGNUM *bn) + { + SHA_CTX sha; + + SHA1_Init(&sha); + hashbn(&sha, bn); + SHA1_Final(md, &sha); + } + +void JPAKE_STEP3A_init(JPAKE_STEP3A *s3a) + {} + +int JPAKE_STEP3A_generate(JPAKE_STEP3A *send, JPAKE_CTX *ctx) + { + quickhashbn(send->hhk, ctx->key); + SHA1(send->hhk, sizeof send->hhk, send->hhk); + + return 1; + } + +int JPAKE_STEP3A_process(JPAKE_CTX *ctx, const JPAKE_STEP3A *received) + { + unsigned char hhk[SHA_DIGEST_LENGTH]; + + quickhashbn(hhk, ctx->key); + SHA1(hhk, sizeof hhk, hhk); + if(memcmp(hhk, received->hhk, sizeof hhk)) + { + JPAKEerr(JPAKE_F_JPAKE_STEP3A_PROCESS, JPAKE_R_HASH_OF_HASH_OF_KEY_MISMATCH); + return 0; + } + return 1; + } + +void JPAKE_STEP3A_release(JPAKE_STEP3A *s3a) + {} + +void JPAKE_STEP3B_init(JPAKE_STEP3B *s3b) + {} + +int JPAKE_STEP3B_generate(JPAKE_STEP3B *send, JPAKE_CTX *ctx) + { + quickhashbn(send->hk, ctx->key); + + return 1; + } + +int JPAKE_STEP3B_process(JPAKE_CTX *ctx, const JPAKE_STEP3B *received) + { + unsigned char hk[SHA_DIGEST_LENGTH]; + + quickhashbn(hk, ctx->key); + if(memcmp(hk, received->hk, sizeof hk)) + { + JPAKEerr(JPAKE_F_JPAKE_STEP3B_PROCESS, JPAKE_R_HASH_OF_KEY_MISMATCH); + return 0; + } + return 1; + } + +void JPAKE_STEP3B_release(JPAKE_STEP3B *s3b) + {} + +const BIGNUM *JPAKE_get_shared_key(JPAKE_CTX *ctx) + { + return ctx->key; + } + |