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Add SM2 ElGamal

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Zhi Guan
2022-10-19 21:31:48 +08:00
parent f906d1c44f
commit 085a4d1310
2 changed files with 298 additions and 0 deletions
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45
include/gmssl/sm2_elgamal.h Normal file
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/*
* Copyright 2014-2022 The GmSSL Project. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the License); you may
* not use this file except in compliance with the License.
*
* http://www.apache.org/licenses/LICENSE-2.0
*/
#ifndef GMSSL_SM2_ELGAMAL_H
#define GMSSL_SM2_ELGAMAL_H
#include <string.h>
#include <stdint.h>
#include <gmssl/sm2.h>
#ifdef __cplusplus
extern "C" {
#endif
typedef uint32_t sm2_elgamal_plaintext_t;
typedef struct {
SM2_POINT C1;
SM2_POINT C2;
} SM2_ELGAMAL_CIPHERTEXT;
int sm2_elgamal_encrypt(const SM2_KEY *pub_key, sm2_elgamal_plaintext_t in, SM2_ELGAMAL_CIPHERTEXT *out);
int sm2_elgamal_decrypt(const SM2_KEY *key, const SM2_ELGAMAL_CIPHERTEXT *in, sm2_elgamal_plaintext_t *out);
int sm2_elgamal_ciphertext_add(SM2_ELGAMAL_CIPHERTEXT *r, const SM2_ELGAMAL_CIPHERTEXT *a, const SM2_ELGAMAL_CIPHERTEXT *b, const SM2_KEY *pub_key);
int sm2_elgamal_cipehrtext_sub(SM2_ELGAMAL_CIPHERTEXT *r, const SM2_ELGAMAL_CIPHERTEXT *a, const SM2_ELGAMAL_CIPHERTEXT *b, const SM2_KEY *pub_key);
int sm2_elgamal_cipehrtext_neg(SM2_ELGAMAL_CIPHERTEXT *r, const SM2_ELGAMAL_CIPHERTEXT *a, const SM2_KEY *pub_key);
int sm2_elgamal_ciphertext_scalar_mul(SM2_ELGAMAL_CIPHERTEXT *r, uint32_t scalar, const SM2_ELGAMAL_CIPHERTEXT *a, const SM2_KEY *pub_key);
int sm2_elgamal_ciphertext_to_der(const SM2_ELGAMAL_CIPHERTEXT *c, uint8_t **out, size_t *outlen);
int sm2_elgamal_ciphertext_from_der(SM2_ELGAMAL_CIPHERTEXT *c, const uint8_t **in, size_t *inlen);
#ifdef __cplusplus
}
#endif
#endif

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src/sm2_elgamal.c Normal file
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/*
* Copyright 2014-2022 The GmSSL Project. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the License); you may
* not use this file except in compliance with the License.
*
* http://www.apache.org/licenses/LICENSE-2.0
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <limits.h>
#include <stdint.h>
#include <gmssl/sm2.h>
#include <gmssl/asn1.h>
#include <gmssl/error.h>
#include "sm2_elgamal.h"
int sm2_elgamal_encrypt(const SM2_KEY *pub_key, sm2_elgamal_plaintext_t in, SM2_ELGAMAL_CIPHERTEXT *out)
{
SM2_Fn k;
uint8_t k_bytes[32];
SM2_Fn m;
uint8_t m_bytes[32];
do {
sm2_fn_rand(k); // FIXME: sm2_fn_rand() return value!
} while (sm2_bn_is_zero(k));
sm2_bn_to_bytes(k, k_bytes);
if (sm2_point_mul_generator(&out->C1, k_bytes) != 1) {
error_print();
return -1;
}
sm2_bn_set_word(m, in);
sm2_bn_to_bytes(m, m_bytes);
if (sm2_point_mul_sum(&out->C2, k_bytes, &pub_key->public_key, m_bytes) != 1) {
error_print();
return -1;
}
return 1;
}
// M = m * G = -[x]C1 + C2
int sm2_elgamal_decrypt(const SM2_KEY *key, const SM2_ELGAMAL_CIPHERTEXT *in, sm2_elgamal_plaintext_t *out)
{
SM2_Fn x;
SM2_JACOBIAN_POINT M;
SM2_JACOBIAN_POINT M_;
SM2_JACOBIAN_POINT C1;
SM2_JACOBIAN_POINT C2;
uint8_t bytes[64];
uint32_t m;
sm2_bn_from_bytes(x, key->private_key);
sm2_jacobian_point_from_bytes(&C1, (const uint8_t *)&in->C1);
sm2_jacobian_point_from_bytes(&C2, (const uint8_t *)&in->C2);
sm2_jacobian_point_mul(&C1, x, &C1);
sm2_jacobian_point_neg(&C1, &C1);
sm2_jacobian_point_add(&M, &C1, &C2);
sm2_jacobian_point_to_bytes(&M, bytes);
sm2_jacobian_point_init(&M_);
// TODO: a real algor required
for (m = 1; m < INT_MAX; m++) {
uint8_t point[64];
sm2_jacobian_point_add(&M_, &M_, SM2_G);
sm2_jacobian_point_to_bytes(&M_, point);
if (memcmp(point, bytes, 64) == 0) {
*out = m;
return 1;
}
}
error_print();
return -1;
}
int test_sm2_elgamal_encrypt(void)
{
SM2_KEY key;
SM2_ELGAMAL_CIPHERTEXT C1;
SM2_ELGAMAL_CIPHERTEXT C2;
sm2_elgamal_plaintext_t m = 1555;
sm2_key_generate(&key);
sm2_elgamal_encrypt(&key, m, &C1);
m = 0;
sm2_elgamal_decrypt(&key, &C1, &m);
printf("m = %u\n", m);
return 1;
}
// ([k1]G, [m1]G + [k1]P) + ([k2]G, [m2]G + [k2]P) =>
// ([k1]G + [k2]G + [r]G, [m1]G + [m2]G + [k1]P + [k2]P + [r]P)
int sm2_elgamal_ciphertext_add(SM2_ELGAMAL_CIPHERTEXT *r,
const SM2_ELGAMAL_CIPHERTEXT *a,
const SM2_ELGAMAL_CIPHERTEXT *b,
const SM2_KEY *pub_key)
{
SM2_Fn k;
SM2_JACOBIAN_POINT A1;
SM2_JACOBIAN_POINT A2;
SM2_JACOBIAN_POINT B1;
SM2_JACOBIAN_POINT B2;
SM2_JACOBIAN_POINT R1;
SM2_JACOBIAN_POINT R2;
sm2_jacobian_point_from_bytes(&A1, (uint8_t *)&a->C1);
sm2_jacobian_point_from_bytes(&A2, (uint8_t *)&a->C2);
sm2_jacobian_point_from_bytes(&B1, (uint8_t *)&b->C1);
sm2_jacobian_point_from_bytes(&B2, (uint8_t *)&b->C2);
sm2_jacobian_point_add(&A1, &A1, &B1);
sm2_jacobian_point_add(&A2, &A2, &B2);
do {
sm2_fn_rand(k);
} while (sm2_bn_is_zero(k));
sm2_jacobian_point_mul_generator(&R1, k);
sm2_jacobian_point_add(&A1, &A1, &R1);
sm2_jacobian_point_from_bytes(&R2, (const uint8_t *)&pub_key->public_key);
sm2_jacobian_point_mul(&R2, k, &R2);
sm2_jacobian_point_add(&A2, &A2, &R2);
sm2_jacobian_point_to_bytes(&A1, (uint8_t *)&r->C1);
sm2_jacobian_point_to_bytes(&A2, (uint8_t *)&r->C2);
return 1;
}
int sm2_elgamal_cipehrtext_sub(SM2_ELGAMAL_CIPHERTEXT *r,
const SM2_ELGAMAL_CIPHERTEXT *a, const SM2_ELGAMAL_CIPHERTEXT *b,
const SM2_KEY *pub_key)
{
error_print();
return -1;
}
int sm2_elgamal_cipehrtext_neg(SM2_ELGAMAL_CIPHERTEXT *r, const SM2_ELGAMAL_CIPHERTEXT *a, const SM2_KEY *pub_key)
{
error_print();
return -1;
}
// s * (C1, C2) := ([s]C1 + [r]G, [s]C2 + [r]P)
int sm2_elgamal_ciphertext_scalar_mul(SM2_ELGAMAL_CIPHERTEXT *r, const uint8_t scalar[32], const SM2_ELGAMAL_CIPHERTEXT *a, const SM2_KEY *pub_key)
{
SM2_BN r;
uint8_t r_bytes[32];
SM2_BN s;
SM2_JACOBIAN_POINT C;
SM2_JACOBIAN_POINT P;
do {
sm2_fn_rand(r); // FIXME: return value
} while (sm2_bn_is_zero(r));
sm2_bn_to_bytes(r, r_bytes);
sm2_point_mul_sum(&r->C1, scalar, &a->C1, r_bytes);
sm2_bn_from_bytes(s, scalar);
sm2_jacobian_point_from_bytes(&C, &a->C2);
sm2_jacobian_point_from_bytes(&P, &pub_key->public_key);
sm2_jacobian_point_mul(&C, s, &C);
sm2_jacobian_point_mul(&P, r, &P);
sm2_jacobian_point_add(&C, &C, &P);
sm2_jacobian_point_to_bytes(&C, (uint8_t *)&r->C2);
return 1;
}
int sm2_elgamal_ciphertext_to_der(const SM2_ELGAMAL_CIPHERTEXT *c, uint8_t **out, size_t *outlen)
{
uint8_t c1[65];
uint8_t c2[65];
size_t len;
sm2_point_to_uncompressed_octets(&c->C1, c1);
sm2_point_to_uncompressed_octets(&c->C2, c2);
if (asn1_octet_string_to_der(c1, sizeof(c1), NULL, &len) != 1
|| asn1_octet_string_to_der(c2, sizeof(c2), NULL, &len) != 1
|| asn1_sequence_header_to_der(len, out, outlen) != 1
|| asn1_octet_string_to_der(c1, sizeof(c1), out, outlen) != 1
|| asn1_octet_string_to_der(c2, sizeof(c2), out, outlen) != 1) {
error_print();
return -1;
}
return 1;
}
int sm2_elgamal_ciphertext_from_der(SM2_ELGAMAL_CIPHERTEXT *c, const uint8_t **in, size_t *inlen)
{
int ret;
const uint8_t *d;
size_t dlen;
const uint8_t *c1;
size_t c1len;
const uint8_t *c2;
size_t c2len;
if ((ret = asn1_sequence_from_der(&d, &dlen, in, inlen)) != 1) {
error_print();
return -1;
}
if (asn1_octet_string_from_der(&c1, &c1len, &d, &dlen) != 1
|| asn1_octet_string_from_der(&c2, &c2len, &d, &dlen) != 1
|| asn1_length_is_zero(dlen) != 1) {
error_print();
return -1;
}
if (sm2_point_from_octets(&c->C1, c1, c1len) != 1
|| sm2_point_from_octets(&c->C2, c2, c2len) != 1) {
error_print();
return -1;
}
return 1;
}
#if 0
int main(void)
{
test_sm2_elgamal_encrypt();
return 0;
}
#endif