sm2有公钥和私钥加解密 C

是的，SM2加密算法支持使用公钥进行加密和私钥进行解密。以下是一个示例代码，展示了如何使用C语言的OpenSSL库来进行SM2的公钥加密和私钥解密：

#include <stdio.h>
#include <string.h>
#include <openssl/evp.h>
#include <openssl/pem.h>

int main() {
    // 加载公钥
    EVP_PKEY *pkey = NULL;
    FILE *public_key_file = fopen("public_key.pem", "r");
    if (public_key_file == NULL) {
        printf("Failed to open public key file.\n");
        return 1;
    }
    pkey = PEM_read_PUBKEY(public_key_file, NULL, NULL, NULL);
    fclose(public_key_file);
    if (pkey == NULL) {
        printf("Failed to load public key.\n");
        return 1;
    }

    // 待加密的明文
    unsigned char plaintext[] = "Hello, SM2!";
    int plaintext_len = strlen((char *)plaintext);

    // 创建EVP加密上下文
    EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
    if (ctx == NULL) {
        printf("Failed to create EVP_CIPHER_CTX.\n");
        EVP_PKEY_free(pkey);
        return 1;
    }

    // 设置加密算法为SM2
    if (!EVP_EncryptInit_ex(ctx, EVP_sm2(), NULL, NULL, NULL)) {
        printf("Failed to set SM2 encryption algorithm.\n");
        EVP_CIPHER_CTX_free(ctx);
        EVP_PKEY_free(pkey);
        return 1;
    }

    // 设置公钥
    if (!EVP_PKEY_CTX_ctrl(pkey->pkey.ctx, -1, EVP_PKEY_OP_ENCRYPT, EVP_PKEY_CTRL_SET_KEY, 32, NULL)) {
        printf("Failed to set public key.\n");
        EVP_CIPHER_CTX_free(ctx);
        EVP_PKEY_free(pkey);
        return 1;
    }

    // 计算加密后的密文长度
    int ciphertext_len = 0;
    if (!EVP_EncryptUpdate(ctx, NULL, &ciphertext_len, plaintext, plaintext_len)) {
        printf("Failed to calculate ciphertext length.\n");
        EVP_CIPHER_CTX_free(ctx);
        EVP_PKEY_free(pkey);
        return 1;
    }

    // 执行加密
    unsigned char ciphertext[ciphertext_len];
    if (!EVP_EncryptUpdate(ctx, ciphertext, &ciphertext_len, plaintext, plaintext_len)) {
        printf("Failed to encrypt.\n");
        EVP_CIPHER_CTX_free(ctx);
        EVP_PKEY_free(pkey);
        return 1;
    }

    // 完成加密
    int final_len;
    if (!EVP_EncryptFinal_ex(ctx, ciphertext + ciphertext_len, &final_len)) {
        printf("Failed to finish encrypt.\n");
        EVP_CIPHER_CTX_free(ctx);
        EVP_PKEY_free(pkey);
        return 1;
    }
    ciphertext_len += final_len;

    // 输出加密结果
    printf("Encrypted ciphertext: ");
    for (int i = 0; i < ciphertext_len; i++) {
        printf("%02X ", ciphertext[i]);
    }
    printf("\n");

    // 解密
    unsigned char decrypted[plaintext_len];
    int decrypted_len = 0;

    // 创建EVP解密上下文
    EVP_CIPHER_CTX *decrypt_ctx = EVP_CIPHER_CTX_new();
    if (decrypt_ctx == NULL) {
        printf("Failed to create EVP_CIPHER_CTX for decryption.\n");
        EVP_CIPHER_CTX_free(ctx);
        EVP_PKEY_free(pkey);
        return 1;
    }

    // 设置解密算法为SM2
    if (!EVP_DecryptInit_ex(decrypt_ctx, EVP_sm2(), NULL, NULL, NULL)) {
        printf("Failed to set SM2 decryption algorithm.\n");
        EVP_CIPHER_CTX_free(ctx);
        EVP_CIPHER_CTX_free(decrypt_ctx);
        EVP_PKEY_free(pkey);
        return 1;
    }

    // 设置私钥
    if (!EVP_PKEY_CTX_ctrl(pkey->pkey.ctx, -1, EVP_PKEY_OP_DECRYPT, EVP_PKEY_CTRL_SET_KEY, 32, NULL)) {
        printf("Failed to set private key.\n");
        EVP_CIPHER_CTX_free(ctx);
        EVP_CIPHER_CTX_free(decrypt_ctx);
        EVP_PKEY_free(pkey);
        return 1;
    }

    // 解密
    if (!EVP_DecryptUpdate(decrypt_ctx, decrypted, &decrypted_len, ciphertext, ciphertext_len)) {
        printf("Failed to decrypt.\n");
        EVP_CIPHER_CTX_free(ctx);
        EVP_CIPHER_CTX_free(decrypt_ctx);
        EVP_PKEY_free(pkey);
        return 1;
    }

    // 完成解密
    int decrypt_final_len;
    if (!EVP_DecryptFinal_ex(decrypt_ctx, decrypted + decrypted_len, &decrypt_final_len)) {
        printf("Failed to finish decrypt.\n");
        EVP_CIPHER_CTX_free(ctx);
        EVP_CIPHER_CTX_free(decrypt_ctx);
        EVP_PKEY_free(pkey);
        return 1;
    }
    decrypted_len += decrypt_final_len;

    // 输出解密结果
    printf("Decrypted plaintext: %s\n", decrypted);

    // 释放资源
    EVP_CIPHER_CTX_free(ctx);
    EVP_CIPHER_CTX_free(decrypt_ctx);
    EVP_PKEY_free(pkey);

    return 0;
}

请注意，上述示例中的公钥文件为`public_key.pem`，私钥文件需要根据实际情况进行加载。

希望这个示例对您有所帮助！如果您有任何其他问题，请随时提问。