# 使用SM2非对称密钥加解密(C/C++)

对应的算法规格请查看非对称密钥加解密算法规格：SM2。

**加密**

1.  调用OH\_CryptoAsymKeyGenerator\_Create、OH\_CryptoAsymKeyGenerator\_Generate，生成SM2密钥类型为SM2\_256的非对称密钥对（keyPair）。keyPair对象中包括公钥PubKey、私钥PriKey。
    
    如何生成SM2非对称密钥对，开发者可参考下文示例，并结合非对称密钥生成和转换规格：SM2和随机生成非对称密钥对理解。参考文档与当前示例可能存在入参差异，请在阅读时注意区分。
    
2.  调用OH\_CryptoAsymCipher\_Create，指定字符串参数'SM2\_256|SM3'，创建非对称密钥类型为SM2\_256、摘要算法为SM3的Cipher实例，用于完成加解密操作。
    
3.  调用OH\_CryptoAsymCipher\_Init，设置模式为加密（CRYPTO\_ENCRYPT\_MODE），指定加密密钥（keyPair），初始化加密Cipher实例。
    
4.  调用OH\_CryptoAsymCipher\_Final，传入明文，获取加密后的数据。
    
    OH\_CryptoAsymCipher\_Final输出结果可能为NULL，在访问具体数据前，需要先判断结果是否为NULL，避免产生异常。
    

**解密**

1.  由于SM2算法的Cipher实例不支持重复init操作，需要调用OH\_CryptoAsymCipher\_Create，重新生成Cipher实例。
    
2.  调用OH\_CryptoAsymCipher\_Init，设置模式为解密（CRYPTO\_DECRYPT\_MODE），指定解密密钥（keyPair）初始化解密Cipher实例。
    
3.  调用OH\_CryptoAsymCipher\_Final，传入密文，获取解密后的数据。
    

```
#include "CryptoArchitectureKit/crypto_architecture_kit.h"
#include <algorithm>
#include <vector>
#include <string>

static std::vector<uint8_t> doTestSm2Enc(OH_CryptoKeyPair *keyPair, std::vector<uint8_t> &plainText)
{
    std::vector<uint8_t> cipherText;
    OH_CryptoAsymCipher *cipher = nullptr;
    OH_Crypto_ErrCode ret = OH_CryptoAsymCipher_Create("SM2_256|SM3", &cipher);
    if (ret != CRYPTO_SUCCESS) {
        return std::vector<uint8_t>{};
    }

    ret = OH_CryptoAsymCipher_Init(cipher, CRYPTO_ENCRYPT_MODE, keyPair);
    if (ret != CRYPTO_SUCCESS) {
        OH_CryptoAsymCipher_Destroy(cipher);
        return std::vector<uint8_t>{};
    }

    Crypto_DataBlob in = {};
    in.data = plainText.data();
    in.len = plainText.size();
    Crypto_DataBlob out = {};
    ret = OH_CryptoAsymCipher_Final(cipher, &in, &out);
    if (ret != CRYPTO_SUCCESS) {
        OH_CryptoAsymCipher_Destroy(cipher);
        return std::vector<uint8_t>{};
    }
    cipherText.insert(cipherText.end(), out.data, out.data + out.len);
    OH_Crypto_FreeDataBlob(&out);

    OH_CryptoAsymCipher_Destroy(cipher);
    return cipherText;
}

static std::vector<uint8_t> doTestSm2Dec(OH_CryptoKeyPair *keyPair, std::vector<uint8_t> &encryptText)
{
    std::vector<uint8_t> decryptText;
    OH_CryptoAsymCipher *cipher = nullptr;
    OH_Crypto_ErrCode ret = OH_CryptoAsymCipher_Create("SM2_256|SM3", &cipher);
    if (ret != CRYPTO_SUCCESS) {
        return std::vector<uint8_t>{};
    }

    ret = OH_CryptoAsymCipher_Init(cipher, CRYPTO_DECRYPT_MODE, keyPair);
    if (ret != CRYPTO_SUCCESS) {
        OH_CryptoAsymCipher_Destroy(cipher);
        return std::vector<uint8_t>{};
    }

    Crypto_DataBlob in = {};
    in.data = encryptText.data();
    in.len = encryptText.size();
    Crypto_DataBlob out = {};
    ret = OH_CryptoAsymCipher_Final(cipher, &in, &out);
    if (ret != CRYPTO_SUCCESS) {
        OH_CryptoAsymCipher_Destroy(cipher);
        return std::vector<uint8_t>{};
    }
    decryptText.insert(decryptText.end(), out.data, out.data + out.len);
    OH_Crypto_FreeDataBlob(&out);

    OH_CryptoAsymCipher_Destroy(cipher);
    return decryptText;
}

OH_Crypto_ErrCode doTestSm2EncMessage()
{
    OH_CryptoAsymKeyGenerator *keyGen = nullptr;
    OH_Crypto_ErrCode ret = OH_CryptoAsymKeyGenerator_Create("SM2_256", &keyGen);
    if (ret != CRYPTO_SUCCESS) {
        return ret;
    }
    OH_CryptoKeyPair *keyPair = nullptr;
    ret = OH_CryptoAsymKeyGenerator_Generate(keyGen, &keyPair);
    if (ret != CRYPTO_SUCCESS) {
        OH_CryptoAsymKeyGenerator_Destroy(keyGen);
        return ret;
    }

    std::string message = "This is a test";
    std::vector<uint8_t> plainText(message.begin(), message.end());
    std::vector<uint8_t> cipherText = doTestSm2Enc(keyPair, plainText);
    std::vector<uint8_t> decryptText = doTestSm2Dec(keyPair, cipherText);

    if ((plainText.size() != decryptText.size()) ||
        (!std::equal(plainText.begin(), plainText.end(), decryptText.begin()))) {
        OH_CryptoKeyPair_Destroy(keyPair);
        OH_CryptoAsymKeyGenerator_Destroy(keyGen);
        return CRYPTO_OPERTION_ERROR;
    }

    OH_CryptoKeyPair_Destroy(keyPair);
    OH_CryptoAsymKeyGenerator_Destroy(keyGen);
    return CRYPTO_SUCCESS;
}
```