sm2 gmssl C语言

SM2是一种国密算法，GMSSL是一个开源的国密加密库，支持C语言等多种编程语言。可以使用GMSSL库来实现SM2算法的加密、解密、签名和验签等操作。

以下是使用GMSSL库实现SM2算法加密和解密的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/ec.h>
#include <openssl/ecdsa.h>
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/sm2.h>
#include <openssl/bn.h>

void print_hex(const char *title, const unsigned char *s, int len)
{
    int i;
    printf("%s", title);
    for (i = 0; i < len; ++i)
        printf("%02X", s[i]);
    printf("\n");
}

int main()
{
    const char *msg = "Hello, SM2!";
    const int msg_len = strlen(msg);

    // Generate random SM2 key pair
    EC_KEY *key = EC_KEY_new_by_curve_name(NID_sm2);
    EC_KEY_generate_key(key);

    // Get public key and private key
    const EC_GROUP *group = EC_KEY_get0_group(key);
    const EC_POINT *pub_key = EC_KEY_get0_public_key(key);
    const BIGNUM *priv_key = EC_KEY_get0_private_key(key);

    // Print public key and private key
    unsigned char *pub_key_buf = NULL;
    int pub_key_len = i2o_ECPublicKey((EC_KEY *)key, &pub_key_buf);
    print_hex("Public key: ", pub_key_buf, pub_key_len);
    unsigned char *priv_key_buf = BN_bn2hex(priv_key);
    printf("Private key: %s\n", priv_key_buf);
    OPENSSL_free(pub_key_buf);
    OPENSSL_free(priv_key_buf);

    // Encrypt message with SM2
    unsigned char *ciphertext = (unsigned char *)malloc(msg_len + 256);
    int ciphertext_len = SM2_encrypt(group, pub_key, (const unsigned char *)msg, msg_len, ciphertext, key);
    print_hex("Ciphertext: ", ciphertext, ciphertext_len);

    // Decrypt ciphertext with SM2
    unsigned char *plaintext = (unsigned char *)malloc(ciphertext_len);
    int plaintext_len = SM2_decrypt(group, priv_key, ciphertext, ciphertext_len, plaintext, key);
    printf("Plaintext: %s\n", plaintext);
    OPENSSL_free(ciphertext);
    OPENSSL_free(plaintext);

    EC_KEY_free(key);
    ERR_free_strings();
    return 0;
}

以上代码包含了SM2加密和解密的完整流程，包括生成随机SM2密钥对、获取公钥和私钥、加密消息、解密密文等。需要注意的是，GMSSL库需要安装并包含相应的头文件和链接库才能正常编译和运行。