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Add SM2 ElGamal
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Zhi Guan
45
include/gmssl/sm2_elgamal.h
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45
include/gmssl/sm2_elgamal.h
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/*
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* Copyright 2014-2022 The GmSSL Project. All Rights Reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*/
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#ifndef GMSSL_SM2_ELGAMAL_H
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#define GMSSL_SM2_ELGAMAL_H
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#include <string.h>
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#include <stdint.h>
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#include <gmssl/sm2.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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typedef uint32_t sm2_elgamal_plaintext_t;
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typedef struct {
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SM2_POINT C1;
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SM2_POINT C2;
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} SM2_ELGAMAL_CIPHERTEXT;
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int sm2_elgamal_encrypt(const SM2_KEY *pub_key, sm2_elgamal_plaintext_t in, SM2_ELGAMAL_CIPHERTEXT *out);
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int sm2_elgamal_decrypt(const SM2_KEY *key, const SM2_ELGAMAL_CIPHERTEXT *in, sm2_elgamal_plaintext_t *out);
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int sm2_elgamal_ciphertext_add(SM2_ELGAMAL_CIPHERTEXT *r, const SM2_ELGAMAL_CIPHERTEXT *a, const SM2_ELGAMAL_CIPHERTEXT *b, const SM2_KEY *pub_key);
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int sm2_elgamal_cipehrtext_sub(SM2_ELGAMAL_CIPHERTEXT *r, const SM2_ELGAMAL_CIPHERTEXT *a, const SM2_ELGAMAL_CIPHERTEXT *b, const SM2_KEY *pub_key);
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int sm2_elgamal_cipehrtext_neg(SM2_ELGAMAL_CIPHERTEXT *r, const SM2_ELGAMAL_CIPHERTEXT *a, const SM2_KEY *pub_key);
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int sm2_elgamal_ciphertext_scalar_mul(SM2_ELGAMAL_CIPHERTEXT *r, uint32_t scalar, const SM2_ELGAMAL_CIPHERTEXT *a, const SM2_KEY *pub_key);
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int sm2_elgamal_ciphertext_to_der(const SM2_ELGAMAL_CIPHERTEXT *c, uint8_t **out, size_t *outlen);
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int sm2_elgamal_ciphertext_from_der(SM2_ELGAMAL_CIPHERTEXT *c, const uint8_t **in, size_t *inlen);
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#ifdef __cplusplus
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}
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#endif
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#endif
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253
src/sm2_elgamal.c
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253
src/sm2_elgamal.c
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/*
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* Copyright 2014-2022 The GmSSL Project. All Rights Reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*/
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <limits.h>
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#include <stdint.h>
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#include <gmssl/sm2.h>
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#include <gmssl/asn1.h>
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#include <gmssl/error.h>
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#include "sm2_elgamal.h"
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int sm2_elgamal_encrypt(const SM2_KEY *pub_key, sm2_elgamal_plaintext_t in, SM2_ELGAMAL_CIPHERTEXT *out)
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{
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SM2_Fn k;
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uint8_t k_bytes[32];
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SM2_Fn m;
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uint8_t m_bytes[32];
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do {
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sm2_fn_rand(k); // FIXME: sm2_fn_rand() return value!
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} while (sm2_bn_is_zero(k));
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sm2_bn_to_bytes(k, k_bytes);
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if (sm2_point_mul_generator(&out->C1, k_bytes) != 1) {
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error_print();
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return -1;
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}
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sm2_bn_set_word(m, in);
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sm2_bn_to_bytes(m, m_bytes);
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if (sm2_point_mul_sum(&out->C2, k_bytes, &pub_key->public_key, m_bytes) != 1) {
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error_print();
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return -1;
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}
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return 1;
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}
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// M = m * G = -[x]C1 + C2
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int sm2_elgamal_decrypt(const SM2_KEY *key, const SM2_ELGAMAL_CIPHERTEXT *in, sm2_elgamal_plaintext_t *out)
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{
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SM2_Fn x;
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SM2_JACOBIAN_POINT M;
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SM2_JACOBIAN_POINT M_;
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SM2_JACOBIAN_POINT C1;
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SM2_JACOBIAN_POINT C2;
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uint8_t bytes[64];
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uint32_t m;
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sm2_bn_from_bytes(x, key->private_key);
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sm2_jacobian_point_from_bytes(&C1, (const uint8_t *)&in->C1);
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sm2_jacobian_point_from_bytes(&C2, (const uint8_t *)&in->C2);
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sm2_jacobian_point_mul(&C1, x, &C1);
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sm2_jacobian_point_neg(&C1, &C1);
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sm2_jacobian_point_add(&M, &C1, &C2);
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sm2_jacobian_point_to_bytes(&M, bytes);
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sm2_jacobian_point_init(&M_);
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// TODO: a real algor required
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for (m = 1; m < INT_MAX; m++) {
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uint8_t point[64];
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sm2_jacobian_point_add(&M_, &M_, SM2_G);
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sm2_jacobian_point_to_bytes(&M_, point);
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if (memcmp(point, bytes, 64) == 0) {
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*out = m;
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return 1;
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}
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}
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error_print();
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return -1;
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}
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int test_sm2_elgamal_encrypt(void)
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{
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SM2_KEY key;
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SM2_ELGAMAL_CIPHERTEXT C1;
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SM2_ELGAMAL_CIPHERTEXT C2;
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sm2_elgamal_plaintext_t m = 1555;
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sm2_key_generate(&key);
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sm2_elgamal_encrypt(&key, m, &C1);
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m = 0;
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sm2_elgamal_decrypt(&key, &C1, &m);
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printf("m = %u\n", m);
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return 1;
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}
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// ([k1]G, [m1]G + [k1]P) + ([k2]G, [m2]G + [k2]P) =>
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// ([k1]G + [k2]G + [r]G, [m1]G + [m2]G + [k1]P + [k2]P + [r]P)
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int sm2_elgamal_ciphertext_add(SM2_ELGAMAL_CIPHERTEXT *r,
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const SM2_ELGAMAL_CIPHERTEXT *a,
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const SM2_ELGAMAL_CIPHERTEXT *b,
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const SM2_KEY *pub_key)
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{
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SM2_Fn k;
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SM2_JACOBIAN_POINT A1;
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SM2_JACOBIAN_POINT A2;
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SM2_JACOBIAN_POINT B1;
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SM2_JACOBIAN_POINT B2;
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SM2_JACOBIAN_POINT R1;
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SM2_JACOBIAN_POINT R2;
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sm2_jacobian_point_from_bytes(&A1, (uint8_t *)&a->C1);
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sm2_jacobian_point_from_bytes(&A2, (uint8_t *)&a->C2);
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sm2_jacobian_point_from_bytes(&B1, (uint8_t *)&b->C1);
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sm2_jacobian_point_from_bytes(&B2, (uint8_t *)&b->C2);
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sm2_jacobian_point_add(&A1, &A1, &B1);
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sm2_jacobian_point_add(&A2, &A2, &B2);
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do {
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sm2_fn_rand(k);
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} while (sm2_bn_is_zero(k));
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sm2_jacobian_point_mul_generator(&R1, k);
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sm2_jacobian_point_add(&A1, &A1, &R1);
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sm2_jacobian_point_from_bytes(&R2, (const uint8_t *)&pub_key->public_key);
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sm2_jacobian_point_mul(&R2, k, &R2);
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sm2_jacobian_point_add(&A2, &A2, &R2);
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sm2_jacobian_point_to_bytes(&A1, (uint8_t *)&r->C1);
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sm2_jacobian_point_to_bytes(&A2, (uint8_t *)&r->C2);
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return 1;
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}
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int sm2_elgamal_cipehrtext_sub(SM2_ELGAMAL_CIPHERTEXT *r,
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const SM2_ELGAMAL_CIPHERTEXT *a, const SM2_ELGAMAL_CIPHERTEXT *b,
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const SM2_KEY *pub_key)
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{
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error_print();
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return -1;
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}
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int sm2_elgamal_cipehrtext_neg(SM2_ELGAMAL_CIPHERTEXT *r, const SM2_ELGAMAL_CIPHERTEXT *a, const SM2_KEY *pub_key)
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{
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error_print();
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return -1;
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}
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// s * (C1, C2) := ([s]C1 + [r]G, [s]C2 + [r]P)
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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)
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{
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SM2_BN r;
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uint8_t r_bytes[32];
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SM2_BN s;
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SM2_JACOBIAN_POINT C;
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SM2_JACOBIAN_POINT P;
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do {
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sm2_fn_rand(r); // FIXME: return value
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} while (sm2_bn_is_zero(r));
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sm2_bn_to_bytes(r, r_bytes);
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sm2_point_mul_sum(&r->C1, scalar, &a->C1, r_bytes);
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sm2_bn_from_bytes(s, scalar);
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sm2_jacobian_point_from_bytes(&C, &a->C2);
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sm2_jacobian_point_from_bytes(&P, &pub_key->public_key);
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sm2_jacobian_point_mul(&C, s, &C);
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sm2_jacobian_point_mul(&P, r, &P);
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sm2_jacobian_point_add(&C, &C, &P);
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sm2_jacobian_point_to_bytes(&C, (uint8_t *)&r->C2);
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return 1;
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}
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int sm2_elgamal_ciphertext_to_der(const SM2_ELGAMAL_CIPHERTEXT *c, uint8_t **out, size_t *outlen)
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{
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uint8_t c1[65];
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uint8_t c2[65];
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size_t len;
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sm2_point_to_uncompressed_octets(&c->C1, c1);
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sm2_point_to_uncompressed_octets(&c->C2, c2);
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if (asn1_octet_string_to_der(c1, sizeof(c1), NULL, &len) != 1
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|| asn1_octet_string_to_der(c2, sizeof(c2), NULL, &len) != 1
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|| asn1_sequence_header_to_der(len, out, outlen) != 1
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|| asn1_octet_string_to_der(c1, sizeof(c1), out, outlen) != 1
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|| asn1_octet_string_to_der(c2, sizeof(c2), out, outlen) != 1) {
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error_print();
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return -1;
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}
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return 1;
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}
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int sm2_elgamal_ciphertext_from_der(SM2_ELGAMAL_CIPHERTEXT *c, const uint8_t **in, size_t *inlen)
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{
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int ret;
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const uint8_t *d;
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size_t dlen;
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const uint8_t *c1;
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size_t c1len;
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const uint8_t *c2;
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size_t c2len;
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if ((ret = asn1_sequence_from_der(&d, &dlen, in, inlen)) != 1) {
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error_print();
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return -1;
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}
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if (asn1_octet_string_from_der(&c1, &c1len, &d, &dlen) != 1
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|| asn1_octet_string_from_der(&c2, &c2len, &d, &dlen) != 1
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|| asn1_length_is_zero(dlen) != 1) {
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error_print();
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return -1;
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}
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if (sm2_point_from_octets(&c->C1, c1, c1len) != 1
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|| sm2_point_from_octets(&c->C2, c2, c2len) != 1) {
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error_print();
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return -1;
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}
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return 1;
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}
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#if 0
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int main(void)
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{
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test_sm2_elgamal_encrypt();
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return 0;
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}
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#endif
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