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#include <alloca.h>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <memory>
#include "crypto.h"
#include "random.h"
namespace crypto {
using std::abort;
using std::int32_t;
using std::int64_t;
using std::size_t;
using std::uint32_t;
using std::uint64_t;
extern "C" {
#include "crypto-ops.h"
}
static inline unsigned char *operator &(ec_point &point) {
return &reinterpret_cast<unsigned char &>(point);
}
static inline const unsigned char *operator &(const ec_point &point) {
return &reinterpret_cast<const unsigned char &>(point);
}
static inline unsigned char *operator &(ec_scalar &scalar) {
return &reinterpret_cast<unsigned char &>(scalar);
}
static inline const unsigned char *operator &(const ec_scalar &scalar) {
return &reinterpret_cast<const unsigned char &>(scalar);
}
static inline void random_scalar(ec_scalar &res) {
unsigned char tmp[64];
generate_random_bytes(64, tmp);
sc_reduce(tmp);
memcpy(&res, tmp, 32);
}
static inline void hash_to_scalar(const void *data, size_t length, ec_scalar &res) {
keccak(data, length, reinterpret_cast<hash &>(res));
sc_reduce32(&res);
}
void crypto_ops::generate_keys(public_key &pub, secret_key &sec) {
ge_p3 point;
random_scalar(sec);
ge_scalarmult_base(&point, &sec);
ge_p3_tobytes(&pub, &point);
}
bool crypto_ops::check_key(const public_key &key) {
ge_p3 point;
return ge_frombytes_vartime(&point, &key) == 0;
}
struct s_comm {
hash h;
ec_point key;
ec_point comm;
};
void crypto_ops::generate_signature(const hash &message_hash, const public_key &pub, const secret_key &sec, signature &sig) {
ge_p3 tmp3;
ec_scalar k;
s_comm buf;
#if !defined(NDEBUG)
{
ge_p3 t;
public_key t2;
assert(sc_check(&sec) == 0);
ge_scalarmult_base(&t, &sec);
ge_p3_tobytes(&t2, &t);
assert(pub == t2);
}
#endif
buf.h = message_hash;
buf.key = pub;
random_scalar(k);
ge_scalarmult_base(&tmp3, &k);
ge_p3_tobytes(&buf.comm, &tmp3);
hash_to_scalar(&buf, sizeof(s_comm), sig.c);
sc_mulsub(&sig.r, &sig.c, &sec, &k);
}
bool crypto_ops::check_signature(const hash &message_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 = message_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;
}
static void hash_to_ec(const public_key &key, ge_p3 &res) {
hash h;
ge_p2 point;
ge_p1p1 point2;
keccak(std::addressof(key), sizeof(public_key), h);
ge_fromfe_frombytes_vartime(&point, reinterpret_cast<const unsigned char *>(&h));
ge_mul8(&point2, &point);
ge_p1p1_to_p3(&res, &point2);
}
void crypto_ops::generate_key_image(const public_key &pub, const secret_key &sec, key_image &image) {
ge_p3 point;
ge_p2 point2;
assert(sc_check(&sec) == 0);
hash_to_ec(pub, point);
ge_scalarmult(&point2, &sec, &point);
ge_tobytes(&image, &point2);
}
struct rs_comm {
hash h;
struct {
ec_point a, b;
} ab[];
};
static inline size_t rs_comm_size(size_t pubs_count) {
return sizeof(rs_comm) + pubs_count * sizeof(rs_comm().ab[0]);
}
void crypto_ops::generate_ring_signature(const hash &message_hash, const key_image &image,
const public_key *const *pubs, size_t pubs_count,
const secret_key &sec, size_t sec_index,
signature *sig) {
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 = message_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);
}
bool crypto_ops::check_ring_signature(const hash &message_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 = message_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;
}
}
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