//subtract Keys (subtracts curve points)
//AB = A - B where A, B are curve points
void subKeys(key & AB, const key &A, const key &B) {
ge_p3 B2, A2;
CHECK_AND_ASSERT_THROW_MES(ge_frombytes_vartime(&B2, B.bytes) == 0, "ge_frombytes_vartime failed at "+boost::lexical_cast<std::string>(__LINE__));
CHECK_AND_ASSERT_THROW_MES(ge_frombytes_vartime(&A2, A.bytes) == 0, "ge_frombytes_vartime failed at "+boost::lexical_cast<std::string>(__LINE__));
ge_cached tmp2;
ge_p3_to_cached(&tmp2, &B2);
ge_p1p1 tmp3;
ge_sub(&tmp3, &A2, &tmp2);
ge_p1p1_to_p3(&A2, &tmp3);
ge_p3_tobytes(AB.bytes, &A2);
}
//addKeys3
//aAbB = a*A + b*B where a, b are scalars, A, B are curve points
//B must be input after applying "precomp"
void addKeys3(key &aAbB, const key &a, const key &A, const key &b, const ge_dsmp B) {
ge_p2 rv;
ge_p3 A2;
CHECK_AND_ASSERT_THROW_MES(ge_frombytes_vartime(&A2, A.bytes) == 0, "ge_frombytes_vartime failed at "+boost::lexical_cast<std::string>(__LINE__));
ge_double_scalarmult_precomp_vartime(&rv, a.bytes, &A2, b.bytes, B);
ge_tobytes(aAbB.bytes, &rv);
}
//addKeys2
//aGbB = aG + bB where a, b are scalars, G is the basepoint and B is a point
void addKeys2(key &aGbB, const key &a, const key &b, const key & B) {
ge_p2 rv;
ge_p3 B2;
CHECK_AND_ASSERT_THROW_MES(ge_frombytes_vartime(&B2, B.bytes) == 0, "ge_frombytes_vartime failed at "+boost::lexical_cast<std::string>(__LINE__));
ge_double_scalarmult_base_vartime(&rv, b.bytes, &B2, a.bytes);
ge_tobytes(aGbB.bytes, &rv);
}
//does a * P where a is a scalar and P is an arbitrary point
void scalarmultKey(key & aP, const key &P, const key &a) {
ge_p3 A;
ge_p2 R;
CHECK_AND_ASSERT_THROW_MES(ge_frombytes_vartime(&A, P.bytes) == 0, "ge_frombytes_vartime failed at "+boost::lexical_cast<std::string>(__LINE__));
ge_scalarmult(&R, a.bytes, &A);
ge_tobytes(aP.bytes, &R);
}
//Computes aH where H= toPoint(cn_fast_hash(G)), G the basepoint
key scalarmultH(const key & a) {
ge_p3 A;
ge_p2 R;
CHECK_AND_ASSERT_THROW_MES(ge_frombytes_vartime(&A, H.bytes) == 0, "ge_frombytes_vartime failed at "+boost::lexical_cast<std::string>(__LINE__));
ge_scalarmult(&R, a.bytes, &A);
key aP;
ge_tobytes(aP.bytes, &R);
return aP;
}
static void corrupt_bob_step2(secure_comparator_t *bob, const void *input, size_t input_length, void *output, size_t *output_length)
{
/* Let's assume bob is malicious and uses zeroes instead of random numbers */
ge_p3 g2a;
ge_p3 g3a;
ge_p3 g2b;
ge_p3 g3b;
ge_frombytes_vartime(&g2a, (const unsigned char *)input);
ge_frombytes_vartime(&g3a, ((const unsigned char *)input) + (3 * ED25519_GE_LENGTH));
if (THEMIS_SCOMPARE_SEND_OUTPUT_TO_PEER != secure_comparator_proceed_compare(bob, input, input_length, output, output_length))
{
testsuite_fail_if(true, "secure_comparator_proceed_compare failed");
return;
}
memset(bob->rand2, 0, sizeof(bob->rand2));
memset(bob->rand3, 0, sizeof(bob->rand3));
ge_scalarmult_base(&g2b, bob->rand2);
ge_scalarmult_base(&g3b, bob->rand3);
ge_scalarmult_blinded(&(bob->g2), bob->rand2, &g2a);
ge_scalarmult_blinded(&(bob->g3), bob->rand3, &g3a);
memset(bob->rand, 0, sizeof(bob->rand));
ge_scalarmult_blinded(&(bob->P), bob->rand, &(bob->g3));
ge_double_scalarmult_vartime((ge_p2 *)&(bob->Q), bob->secret, &(bob->g2), bob->rand);
ge_p2_to_p3(&(bob->Q), (const ge_p2 *)&(bob->Q));
ge_p3_tobytes((unsigned char *)output, &g2b);
ed_sign(3, bob->rand2, ((unsigned char *)output) + ED25519_GE_LENGTH);
ge_p3_tobytes(((unsigned char *)output) + (3 * ED25519_GE_LENGTH), &g3b);
ed_sign(4, bob->rand3, ((unsigned char *)output) + (4 * ED25519_GE_LENGTH));
ge_p3_tobytes(((unsigned char *)output) + (6 * ED25519_GE_LENGTH), &(bob->P));
ge_p3_tobytes(((unsigned char *)output) + (7 * ED25519_GE_LENGTH), &(bob->Q));
ed_dbl_base_sign(5, bob->rand, bob->secret, &(bob->g2), &(bob->g3), ((unsigned char *)output) + (8 * ED25519_GE_LENGTH));
}
bool crypto_ops::check_ring_signature(const hash &prefix_hash, const key_image &image,
const public_key *const *pubs, size_t pubs_count,
const signature *sig) {
size_t i;
ge_p3 image_unp;
ge_dsmp image_pre;
ec_scalar sum, h;
rs_comm *const buf = reinterpret_cast<rs_comm *>(alloca(rs_comm_size(pubs_count)));
#if !defined(NDEBUG)
for (i = 0; i < pubs_count; i++) {
assert(check_key(*pubs[i]));
}
#endif
if (ge_frombytes_vartime(&image_unp, &image) != 0) {
return false;
}
ge_dsm_precomp(image_pre, &image_unp);
sc_0(&sum);
buf->h = prefix_hash;
for (i = 0; i < pubs_count; i++) {
ge_p2 tmp2;
ge_p3 tmp3;
if (sc_check(&sig[i].c) != 0 || sc_check(&sig[i].r) != 0) {
return false;
}
if (ge_frombytes_vartime(&tmp3, &*pubs[i]) != 0) {
abort();
}
ge_double_scalarmult_base_vartime(&tmp2, &sig[i].c, &tmp3, &sig[i].r);
ge_tobytes(&buf->ab[i].a, &tmp2);
hash_to_ec(*pubs[i], tmp3);
ge_double_scalarmult_precomp_vartime(&tmp2, &sig[i].r, &tmp3, &sig[i].c, image_pre);
ge_tobytes(&buf->ab[i].b, &tmp2);
sc_add(&sum, &sum, &sig[i].c);
}
hash_to_scalar(buf, rs_comm_size(pubs_count), h);
sc_sub(&h, &h, &sum);
return sc_isnonzero(&h) == 0;
}
key hashToPointSimple(const key & hh) {
key pointk;
ge_p1p1 point2;
ge_p2 point;
ge_p3 res;
key h = cn_fast_hash(hh);
CHECK_AND_ASSERT_THROW_MES(ge_frombytes_vartime(&res, h.bytes) == 0, "ge_frombytes_vartime failed at "+boost::lexical_cast<std::string>(__LINE__));
ge_p3_to_p2(&point, &res);
ge_mul8(&point2, &point);
ge_p1p1_to_p3(&res, &point2);
ge_p3_tobytes(pointk.bytes, &res);
return pointk;
}
bool crypto_ops::generate_key_derivation(const public_key &key1, const secret_key &key2, key_derivation &derivation) {
ge_p3 point;
ge_p2 point2;
ge_p1p1 point3;
assert(sc_check(&key2) == 0);
if (ge_frombytes_vartime(&point, &key1) != 0) {
return false;
}
ge_scalarmult(&point2, &key2, &point);
ge_mul8(&point3, &point2);
ge_p1p1_to_p2(&point2, &point3);
ge_tobytes(&derivation, &point2);
return true;
}
bool crypto_ops::derive_public_key(const key_derivation &derivation, size_t output_index,
const public_key &base, public_key &derived_key) {
ec_scalar scalar;
ge_p3 point1;
ge_p3 point2;
ge_cached point3;
ge_p1p1 point4;
ge_p2 point5;
if (ge_frombytes_vartime(&point1, &base) != 0) {
return false;
}
derivation_to_scalar(derivation, output_index, scalar);
ge_scalarmult_base(&point2, &scalar);
ge_p3_to_cached(&point3, &point2);
ge_add(&point4, &point1, &point3);
ge_p1p1_to_p2(&point5, &point4);
ge_tobytes(&derived_key, &point5);
return true;
}
bool crypto_ops::check_signature(const hash &prefix_hash, const public_key &pub, const signature &sig) {
ge_p2 tmp2;
ge_p3 tmp3;
ec_scalar c;
s_comm buf;
assert(check_key(pub));
buf.h = prefix_hash;
buf.key = pub;
if (ge_frombytes_vartime(&tmp3, &pub) != 0) {
abort();
}
if (sc_check(&sig.c) != 0 || sc_check(&sig.r) != 0) {
return false;
}
ge_double_scalarmult_base_vartime(&tmp2, &sig.c, &tmp3, &sig.r);
ge_tobytes(&buf.comm, &tmp2);
hash_to_scalar(&buf, sizeof(s_comm), c);
sc_sub(&c, &c, &sig.c);
return sc_isnonzero(&c) == 0;
}
bool crypto_ops::check_key(const public_key &key) {
ge_p3 point;
return ge_frombytes_vartime(&point, &key) == 0;
}
void crypto_ops::generate_ring_signature(const hash &prefix_hash, const key_image &image,
const public_key *const *pubs, size_t pubs_count,
const secret_key &sec, size_t sec_index,
signature *sig) {
lock_guard<mutex> lock(random_lock);
size_t i;
ge_p3 image_unp;
ge_dsmp image_pre;
ec_scalar sum, k, h;
rs_comm *const buf = reinterpret_cast<rs_comm *>(alloca(rs_comm_size(pubs_count)));
assert(sec_index < pubs_count);
#if !defined(NDEBUG)
{
ge_p3 t;
public_key t2;
key_image t3;
assert(sc_check(&sec) == 0);
ge_scalarmult_base(&t, &sec);
ge_p3_tobytes(&t2, &t);
assert(*pubs[sec_index] == t2);
generate_key_image(*pubs[sec_index], sec, t3);
assert(image == t3);
for (i = 0; i < pubs_count; i++) {
assert(check_key(*pubs[i]));
}
}
#endif
if (ge_frombytes_vartime(&image_unp, &image) != 0) {
abort();
}
ge_dsm_precomp(image_pre, &image_unp);
sc_0(&sum);
buf->h = prefix_hash;
for (i = 0; i < pubs_count; i++) {
ge_p2 tmp2;
ge_p3 tmp3;
if (i == sec_index) {
random_scalar(k);
ge_scalarmult_base(&tmp3, &k);
ge_p3_tobytes(&buf->ab[i].a, &tmp3);
hash_to_ec(*pubs[i], tmp3);
ge_scalarmult(&tmp2, &k, &tmp3);
ge_tobytes(&buf->ab[i].b, &tmp2);
} else {
random_scalar(sig[i].c);
random_scalar(sig[i].r);
if (ge_frombytes_vartime(&tmp3, &*pubs[i]) != 0) {
abort();
}
ge_double_scalarmult_base_vartime(&tmp2, &sig[i].c, &tmp3, &sig[i].r);
ge_tobytes(&buf->ab[i].a, &tmp2);
hash_to_ec(*pubs[i], tmp3);
ge_double_scalarmult_precomp_vartime(&tmp2, &sig[i].r, &tmp3, &sig[i].c, image_pre);
ge_tobytes(&buf->ab[i].b, &tmp2);
sc_add(&sum, &sum, &sig[i].c);
}
}
hash_to_scalar(buf, rs_comm_size(pubs_count), h);
sc_sub(&sig[sec_index].c, &h, &sum);
sc_mulsub(&sig[sec_index].r, &sig[sec_index].c, &sec, &k);
}
//Does some precomputation to make addKeys3 more efficient
// input B a curve point and output a ge_dsmp which has precomputation applied
void precomp(ge_dsmp rv, const key & B) {
ge_p3 B2;
CHECK_AND_ASSERT_THROW_MES(ge_frombytes_vartime(&B2, B.bytes) == 0, "ge_frombytes_vartime failed at "+boost::lexical_cast<std::string>(__LINE__));
ge_dsm_precomp(rv, &B2);
}
