4rkal/monero
1
0
Fork 0
mirror of https://github.com/monero-project/monero.git synced 2025-02-07 16:43:41 +02:00
Code Issues Actions 5 Packages Projects Releases Wiki Activity
564fa30966
monero/src/crypto/crypto.cpp
j-berman ea87b30f89 Add view tags to outputs to reduce wallet scanning time 
Implements view tags as proposed by @UkoeHB in MRL issue
https://github.com/monero-project/research-lab/issues/73

At tx construction, the sender adds a 1-byte view tag to each
output. The view tag is derived from the sender-receiver
shared secret. When scanning for outputs, the receiver can
check the view tag for a match, in order to reduce scanning
time. When the view tag does not match, the wallet avoids the
more expensive EC operations when deriving the output public
key using the shared secret.
2022-04-18 00:49:53 -07:00

777 lines
24 KiB
C++
Raw Blame History

// Copyright (c) 2014-2022, The Monero Project
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, are
// permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this list of
// conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice, this list
// of conditions and the following disclaimer in the documentation and/or other
// materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its contributors may be
// used to endorse or promote products derived from this software without specific
// prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
#include <unistd.h>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <boost/thread/mutex.hpp>
#include <boost/thread/lock_guard.hpp>
#include <boost/shared_ptr.hpp>
#include "common/varint.h"
#include "warnings.h"
#include "crypto.h"
#include "hash.h"
#include "cryptonote_config.h"
namespace {
static void local_abort(const char *msg)
{
fprintf(stderr, "%s\n", msg);
#ifdef NDEBUG
_exit(1);
#else
abort();
#endif
}
}
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"
#include "random.h"
}
const crypto::public_key null_pkey = crypto::public_key{};
const crypto::secret_key null_skey = crypto::secret_key{};
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);
}
boost::mutex &get_random_lock()
{
static boost::mutex random_lock;
return random_lock;
}
void generate_random_bytes_thread_safe(size_t N, uint8_t *bytes)
{
boost::lock_guard<boost::mutex> lock(get_random_lock());
generate_random_bytes_not_thread_safe(N, bytes);
}
void add_extra_entropy_thread_safe(const void *ptr, size_t bytes)
{
boost::lock_guard<boost::mutex> lock(get_random_lock());
add_extra_entropy_not_thread_safe(ptr, bytes);
}
static inline bool less32(const unsigned char *k0, const unsigned char *k1)
{
for (int n = 31; n >= 0; --n)
{
if (k0[n] < k1[n])
return true;
if (k0[n] > k1[n])
return false;
}
return false;
}
void random32_unbiased(unsigned char *bytes)
{
// l = 2^252 + 27742317777372353535851937790883648493.
// l fits 15 times in 32 bytes (iow, 15 l is the highest multiple of l that fits in 32 bytes)
static const unsigned char limit[32] = { 0xe3, 0x6a, 0x67, 0x72, 0x8b, 0xce, 0x13, 0x29, 0x8f, 0x30, 0x82, 0x8c, 0x0b, 0xa4, 0x10, 0x39, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf0 };
while(1)
{
generate_random_bytes_thread_safe(32, bytes);
if (!less32(bytes, limit))
continue;
sc_reduce32(bytes);
if (sc_isnonzero(bytes))
break;
}
}
/* generate a random 32-byte (256-bit) integer and copy it to res */
static inline void random_scalar(ec_scalar &res) {
random32_unbiased((unsigned char*)res.data);
}
void hash_to_scalar(const void *data, size_t length, ec_scalar &res) {
cn_fast_hash(data, length, reinterpret_cast<hash &>(res));
sc_reduce32(&res);
}
/*
* generate public and secret keys from a random 256-bit integer
* TODO: allow specifying random value (for wallet recovery)
*
*/
secret_key crypto_ops::generate_keys(public_key &pub, secret_key &sec, const secret_key& recovery_key, bool recover) {
ge_p3 point;
secret_key rng;
if (recover)
{
rng = recovery_key;
}
else
{
random_scalar(rng);
}
sec = rng;
sc_reduce32(&unwrap(sec)); // reduce in case second round of keys (sendkeys)
ge_scalarmult_base(&point, &unwrap(sec));
ge_p3_tobytes(&pub, &point);
return rng;
}
bool crypto_ops::check_key(const public_key &key) {
ge_p3 point;
return ge_frombytes_vartime(&point, &key) == 0;
}
bool crypto_ops::secret_key_to_public_key(const secret_key &sec, public_key &pub) {
ge_p3 point;
if (sc_check(&unwrap(sec)) != 0) {
return false;
}
ge_scalarmult_base(&point, &unwrap(sec));
ge_p3_tobytes(&pub, &point);
return true;
}
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, &unwrap(key2), &point);
ge_mul8(&point3, &point2);
ge_p1p1_to_p2(&point2, &point3);
ge_tobytes(&derivation, &point2);
return true;
}
void crypto_ops::derivation_to_scalar(const key_derivation &derivation, size_t output_index, ec_scalar &res) {
struct {
key_derivation derivation;
char output_index[(sizeof(size_t) * 8 + 6) / 7];
} buf;
char *end = buf.output_index;
buf.derivation = derivation;
tools::write_varint(end, output_index);
assert(end <= buf.output_index + sizeof buf.output_index);
hash_to_scalar(&buf, end - reinterpret_cast<char *>(&buf), res);
}
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;
}
void crypto_ops::derive_secret_key(const key_derivation &derivation, size_t output_index,
const secret_key &base, secret_key &derived_key) {
ec_scalar scalar;
assert(sc_check(&base) == 0);
derivation_to_scalar(derivation, output_index, scalar);
sc_add(&unwrap(derived_key), &unwrap(base), &scalar);
}
bool crypto_ops::derive_subaddress_public_key(const public_key &out_key, const key_derivation &derivation, std::size_t output_index, 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, &out_key) != 0) {
return false;
}
derivation_to_scalar(derivation, output_index, scalar);
ge_scalarmult_base(&point2, &scalar);
ge_p3_to_cached(&point3, &point2);
ge_sub(&point4, &point1, &point3);
ge_p1p1_to_p2(&point5, &point4);
ge_tobytes(&derived_key, &point5);
return true;
}
struct s_comm {
hash h;
ec_point key;
ec_point comm;
};
// Used in v1 tx proofs
struct s_comm_2_v1 {
hash msg;
ec_point D;
ec_point X;
ec_point Y;
};
// Used in v1/v2 tx proofs
struct s_comm_2 {
hash msg;
ec_point D;
ec_point X;
ec_point Y;
hash sep; // domain separation
ec_point R;
ec_point A;
ec_point B;
};
void crypto_ops::generate_signature(const hash &prefix_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 = prefix_hash;
buf.key = pub;
try_again:
random_scalar(k);
ge_scalarmult_base(&tmp3, &k);
ge_p3_tobytes(&buf.comm, &tmp3);
hash_to_scalar(&buf, sizeof(s_comm), sig.c);
if (!sc_isnonzero((const unsigned char*)sig.c.data))
goto try_again;
sc_mulsub(&sig.r, &sig.c, &unwrap(sec), &k);
if (!sc_isnonzero((const unsigned char*)sig.r.data))
goto try_again;
memwipe(&k, sizeof(k));
}
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) {
return false;
}
if (sc_check(&sig.c) != 0 || sc_check(&sig.r) != 0 || !sc_isnonzero(&sig.c)) {
return false;
}
ge_double_scalarmult_base_vartime(&tmp2, &sig.c, &tmp3, &sig.r);
ge_tobytes(&buf.comm, &tmp2);
static const ec_point infinity = {{ 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}};
if (memcmp(&buf.comm, &infinity, 32) == 0)
return false;
hash_to_scalar(&buf, sizeof(s_comm), c);
sc_sub(&c, &c, &sig.c);
return sc_isnonzero(&c) == 0;
}
// Generate a proof of knowledge of `r` such that (`R = rG` and `D = rA`) or (`R = rB` and `D = rA`) via a Schnorr proof
// This handles use cases for both standard addresses and subaddresses
//
// NOTE: This generates old v1 proofs, and is for TESTING ONLY
void crypto_ops::generate_tx_proof_v1(const hash &prefix_hash, const public_key &R, const public_key &A, const boost::optional<public_key> &B, const public_key &D, const secret_key &r, signature &sig) {
// sanity check
ge_p3 R_p3;
ge_p3 A_p3;
ge_p3 B_p3;
ge_p3 D_p3;
if (ge_frombytes_vartime(&R_p3, &R) != 0) throw std::runtime_error("tx pubkey is invalid");
if (ge_frombytes_vartime(&A_p3, &A) != 0) throw std::runtime_error("recipient view pubkey is invalid");
if (B && ge_frombytes_vartime(&B_p3, &*B) != 0) throw std::runtime_error("recipient spend pubkey is invalid");
if (ge_frombytes_vartime(&D_p3, &D) != 0) throw std::runtime_error("key derivation is invalid");
#if !defined(NDEBUG)
{
assert(sc_check(&r) == 0);
// check R == r*G or R == r*B
public_key dbg_R;
if (B)
{
ge_p2 dbg_R_p2;
ge_scalarmult(&dbg_R_p2, &r, &B_p3);
ge_tobytes(&dbg_R, &dbg_R_p2);
}
else
{
ge_p3 dbg_R_p3;
ge_scalarmult_base(&dbg_R_p3, &r);
ge_p3_tobytes(&dbg_R, &dbg_R_p3);
}
assert(R == dbg_R);
// check D == r*A
ge_p2 dbg_D_p2;
ge_scalarmult(&dbg_D_p2, &r, &A_p3);
public_key dbg_D;
ge_tobytes(&dbg_D, &dbg_D_p2);
assert(D == dbg_D);
}
#endif
// pick random k
ec_scalar k;
random_scalar(k);
s_comm_2_v1 buf;
buf.msg = prefix_hash;
buf.D = D;
if (B)
{
// compute X = k*B
ge_p2 X_p2;
ge_scalarmult(&X_p2, &k, &B_p3);
ge_tobytes(&buf.X, &X_p2);
}
else
{
// compute X = k*G
ge_p3 X_p3;
ge_scalarmult_base(&X_p3, &k);
ge_p3_tobytes(&buf.X, &X_p3);
}
// compute Y = k*A
ge_p2 Y_p2;
ge_scalarmult(&Y_p2, &k, &A_p3);
ge_tobytes(&buf.Y, &Y_p2);
// sig.c = Hs(Msg || D || X || Y)
hash_to_scalar(&buf, sizeof(buf), sig.c);
// sig.r = k - sig.c*r
sc_mulsub(&sig.r, &sig.c, &unwrap(r), &k);
}
// Generate a proof of knowledge of `r` such that (`R = rG` and `D = rA`) or (`R = rB` and `D = rA`) via a Schnorr proof
// This handles use cases for both standard addresses and subaddresses
//
// Generates only proofs for InProofV2 and OutProofV2
void crypto_ops::generate_tx_proof(const hash &prefix_hash, const public_key &R, const public_key &A, const boost::optional<public_key> &B, const public_key &D, const secret_key &r, signature &sig) {
// sanity check
ge_p3 R_p3;
ge_p3 A_p3;
ge_p3 B_p3;
ge_p3 D_p3;
if (ge_frombytes_vartime(&R_p3, &R) != 0) throw std::runtime_error("tx pubkey is invalid");
if (ge_frombytes_vartime(&A_p3, &A) != 0) throw std::runtime_error("recipient view pubkey is invalid");
if (B && ge_frombytes_vartime(&B_p3, &*B) != 0) throw std::runtime_error("recipient spend pubkey is invalid");
if (ge_frombytes_vartime(&D_p3, &D) != 0) throw std::runtime_error("key derivation is invalid");
#if !defined(NDEBUG)
{
assert(sc_check(&r) == 0);
// check R == r*G or R == r*B
public_key dbg_R;
if (B)
{
ge_p2 dbg_R_p2;
ge_scalarmult(&dbg_R_p2, &r, &B_p3);
ge_tobytes(&dbg_R, &dbg_R_p2);
}
else
{
ge_p3 dbg_R_p3;
ge_scalarmult_base(&dbg_R_p3, &r);
ge_p3_tobytes(&dbg_R, &dbg_R_p3);
}
assert(R == dbg_R);
// check D == r*A
ge_p2 dbg_D_p2;
ge_scalarmult(&dbg_D_p2, &r, &A_p3);
public_key dbg_D;
ge_tobytes(&dbg_D, &dbg_D_p2);
assert(D == dbg_D);
}
#endif
// pick random k
ec_scalar k;
random_scalar(k);
// if B is not present
static const ec_point zero = {{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }};
s_comm_2 buf;
buf.msg = prefix_hash;
buf.D = D;
buf.R = R;
buf.A = A;
if (B)
buf.B = *B;
else
buf.B = zero;
cn_fast_hash(config::HASH_KEY_TXPROOF_V2, sizeof(config::HASH_KEY_TXPROOF_V2)-1, buf.sep);
if (B)
{
// compute X = k*B
ge_p2 X_p2;
ge_scalarmult(&X_p2, &k, &B_p3);
ge_tobytes(&buf.X, &X_p2);
}
else
{
// compute X = k*G
ge_p3 X_p3;
ge_scalarmult_base(&X_p3, &k);
ge_p3_tobytes(&buf.X, &X_p3);
}
// compute Y = k*A
ge_p2 Y_p2;
ge_scalarmult(&Y_p2, &k, &A_p3);
ge_tobytes(&buf.Y, &Y_p2);
// sig.c = Hs(Msg || D || X || Y || sep || R || A || B)
hash_to_scalar(&buf, sizeof(buf), sig.c);
// sig.r = k - sig.c*r
sc_mulsub(&sig.r, &sig.c, &unwrap(r), &k);
memwipe(&k, sizeof(k));
}
// Verify a proof: either v1 (version == 1) or v2 (version == 2)
bool crypto_ops::check_tx_proof(const hash &prefix_hash, const public_key &R, const public_key &A, const boost::optional<public_key> &B, const public_key &D, const signature &sig, const int version) {
// sanity check
ge_p3 R_p3;
ge_p3 A_p3;
ge_p3 B_p3;
ge_p3 D_p3;
if (ge_frombytes_vartime(&R_p3, &R) != 0) return false;
if (ge_frombytes_vartime(&A_p3, &A) != 0) return false;
if (B && ge_frombytes_vartime(&B_p3, &*B) != 0) return false;
if (ge_frombytes_vartime(&D_p3, &D) != 0) return false;
if (sc_check(&sig.c) != 0 || sc_check(&sig.r) != 0) return false;
// compute sig.c*R
ge_p3 cR_p3;
{
ge_p2 cR_p2;
ge_scalarmult(&cR_p2, &sig.c, &R_p3);
public_key cR;
ge_tobytes(&cR, &cR_p2);
if (ge_frombytes_vartime(&cR_p3, &cR) != 0) return false;
}
ge_p1p1 X_p1p1;
if (B)
{
// compute X = sig.c*R + sig.r*B
ge_p2 rB_p2;
ge_scalarmult(&rB_p2, &sig.r, &B_p3);
public_key rB;
ge_tobytes(&rB, &rB_p2);
ge_p3 rB_p3;
if (ge_frombytes_vartime(&rB_p3, &rB) != 0) return false;
ge_cached rB_cached;
ge_p3_to_cached(&rB_cached, &rB_p3);
ge_add(&X_p1p1, &cR_p3, &rB_cached);
}
else
{
// compute X = sig.c*R + sig.r*G
ge_p3 rG_p3;
ge_scalarmult_base(&rG_p3, &sig.r);
ge_cached rG_cached;
ge_p3_to_cached(&rG_cached, &rG_p3);
ge_add(&X_p1p1, &cR_p3, &rG_cached);
}
ge_p2 X_p2;
ge_p1p1_to_p2(&X_p2, &X_p1p1);
// compute sig.c*D
ge_p2 cD_p2;
ge_scalarmult(&cD_p2, &sig.c, &D_p3);
// compute sig.r*A
ge_p2 rA_p2;
ge_scalarmult(&rA_p2, &sig.r, &A_p3);
// compute Y = sig.c*D + sig.r*A
public_key cD;
public_key rA;
ge_tobytes(&cD, &cD_p2);
ge_tobytes(&rA, &rA_p2);
ge_p3 cD_p3;
ge_p3 rA_p3;
if (ge_frombytes_vartime(&cD_p3, &cD) != 0) return false;
if (ge_frombytes_vartime(&rA_p3, &rA) != 0) return false;
ge_cached rA_cached;
ge_p3_to_cached(&rA_cached, &rA_p3);
ge_p1p1 Y_p1p1;
ge_add(&Y_p1p1, &cD_p3, &rA_cached);
ge_p2 Y_p2;
ge_p1p1_to_p2(&Y_p2, &Y_p1p1);
// Compute hash challenge
// for v1, c2 = Hs(Msg || D || X || Y)
// for v2, c2 = Hs(Msg || D || X || Y || sep || R || A || B)
// if B is not present
static const ec_point zero = {{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }};
s_comm_2 buf;
buf.msg = prefix_hash;
buf.D = D;
buf.R = R;
buf.A = A;
if (B)
buf.B = *B;
else
buf.B = zero;
cn_fast_hash(config::HASH_KEY_TXPROOF_V2, sizeof(config::HASH_KEY_TXPROOF_V2)-1, buf.sep);
ge_tobytes(&buf.X, &X_p2);
ge_tobytes(&buf.Y, &Y_p2);
ec_scalar c2;
// Hash depends on version
if (version == 1) hash_to_scalar(&buf, sizeof(s_comm_2) - 3*sizeof(ec_point) - sizeof(hash), c2);
else if (version == 2) hash_to_scalar(&buf, sizeof(s_comm_2), c2);
else return false;
// test if c2 == sig.c
sc_sub(&c2, &c2, &sig.c);
return sc_isnonzero(&c2) == 0;
}
static void hash_to_ec(const public_key &key, ge_p3 &res) {
hash h;
ge_p2 point;
ge_p1p1 point2;
cn_fast_hash(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, &unwrap(sec), &point);
ge_tobytes(&image, &point2);
}
PUSH_WARNINGS
DISABLE_VS_WARNINGS(4200)
struct ec_point_pair {
ec_point a, b;
};
struct rs_comm {
hash h;
struct ec_point_pair ab[];
};
POP_WARNINGS
static inline size_t rs_comm_size(size_t pubs_count) {
return sizeof(rs_comm) + pubs_count * sizeof(ec_point_pair);
}
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) {
size_t i;
ge_p3 image_unp;
ge_dsmp image_pre;
ec_scalar sum, k, h;
boost::shared_ptr<rs_comm> buf(reinterpret_cast<rs_comm *>(malloc(rs_comm_size(pubs_count))), free);
if (!buf)
local_abort("malloc failure");
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) {
local_abort("invalid key image");
}
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) {
memwipe(&k, sizeof(k));
local_abort("invalid pubkey");
}
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.get(), rs_comm_size(pubs_count), h);
sc_sub(&sig[sec_index].c, &h, &sum);
sc_mulsub(&sig[sec_index].r, &sig[sec_index].c, &unwrap(sec), &k);
memwipe(&k, sizeof(k));
}
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;
boost::shared_ptr<rs_comm> buf(reinterpret_cast<rs_comm *>(malloc(rs_comm_size(pubs_count))), free);
if (!buf)
return false;
#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) {
return false;
}
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.get(), rs_comm_size(pubs_count), h);
sc_sub(&h, &h, &sum);
return sc_isnonzero(&h) == 0;
}
void crypto_ops::derive_view_tag(const key_derivation &derivation, size_t output_index, view_tag &view_tag) {
#pragma pack(push, 1)
struct {
char salt[8]; // view tag domain-separator
key_derivation derivation;
char output_index[(sizeof(size_t) * 8 + 6) / 7];
} buf;
#pragma pack(pop)
char *end = buf.output_index;
memcpy(buf.salt, "view_tag", 8); // leave off null terminator
buf.derivation = derivation;
tools::write_varint(end, output_index);
assert(end <= buf.output_index + sizeof buf.output_index);
// view_tag_full = H[salt|derivation|output_index]
hash view_tag_full;
cn_fast_hash(&buf, end - reinterpret_cast<char *>(&buf), view_tag_full);
// only need a slice of view_tag_full to realize optimal perf/space efficiency
static_assert(sizeof(crypto::view_tag) <= sizeof(view_tag_full), "view tag should not be larger than hash result");
memcpy(&view_tag, &view_tag_full, sizeof(crypto::view_tag));
}
}
Reference in New Issue View Git Blame Copy Permalink