# 使用SM2密钥对验签(C/C++)


对应的算法规格请查看[验签算法规格：SM2](crypto-sign-sig-verify-overview.md#sm2)。


## 在CMake脚本中链接相关动态库
```txt
   target_link_libraries(entry PUBLIC libohcrypto.so)
```

## 开发步骤


1. 调用[OH_CryptoVerify_Create](../../reference/apis-crypto-architecture-kit/_crypto_signature_api.md#oh_cryptoverify_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Verify实例，用于完成验签操作。

2. 调用[OH_CryptoVerify_Init](../../reference/apis-crypto-architecture-kit/_crypto_signature_api.md#oh_cryptoverify_init)，使用公钥（OH_CryptoPubKey）初始化Verify实例。

3. 调用[OH_CryptoVerify_Update](../../reference/apis-crypto-architecture-kit/_crypto_signature_api.md#oh_cryptoverify_update)，传入待验证的数据。
   当前单次update长度没有限制，开发者可以根据数据量判断如何调用update，如果数据量较小，可以直接调用OH_CryptoVerify_Final接口一次性传入。

4. 调用[OH_CryptoVerify_Final](../../reference/apis-crypto-architecture-kit/_crypto_signature_api.md#oh_cryptoverify_final)，对数据进行验签。



```c++
#include "CryptoArchitectureKit/crypto_common.h"
#include "CryptoArchitectureKit/crypto_signature.h"
#include "CryptoArchitectureKit/crypto_asym_key.h"

static bool doTestSm2Signature()
{
   OH_CryptoAsymKeyGenerator *keyCtx = nullptr;
   OH_CryptoKeyPair *keyPair = nullptr;
   OH_CryptoVerify *verify = nullptr;

   uint8_t plainText[] = {
      0x96, 0x46, 0x2e, 0xde, 0x3f, 0x47, 0xbf, 0xd6, 0x87, 0x48, 0x36, 0x1d, 0x75, 0x35, 0xbd, 0xbc,
      0x6b, 0x06, 0xe8, 0xb3, 0x68, 0x91, 0x53, 0xce, 0x76, 0x5d, 0x24, 0xda, 0xdc, 0xc4, 0x9f, 0x94,
   };
   Crypto_DataBlob msgBlob = {
      .data = reinterpret_cast<uint8_t *>(plainText),
      .len = sizeof(plainText)
   };

   uint8_t pubKeyText[] = {
      0x30, 0x59, 0x30, 0x13, 0x06, 0x07, 0x2a, 0x86, 0x48, 0xce, 0x3d, 0x02, 0x01, 0x06, 0x08, 0x2a,
      0x81, 0x1c, 0xcf, 0x55, 0x01, 0x82, 0x2d, 0x03, 0x42, 0x00, 0x04, 0x80, 0x5b, 0x78, 0x04, 0xd7,
      0xcf, 0xc3, 0x99, 0x63, 0xae, 0x88, 0xcd, 0xfc, 0xd6, 0x18, 0xf4, 0x08, 0xe8, 0xe3, 0x68, 0x47,
      0x4f, 0x44, 0x0e, 0xb2, 0xba, 0x3a, 0xb3, 0x10, 0xf1, 0xc9, 0xd0, 0x84, 0xe2, 0xa4, 0x47, 0xbe,
      0x72, 0xae, 0xf8, 0x6a, 0xeb, 0x6e, 0x10, 0xab, 0x52, 0x6b, 0x6a, 0x58, 0xc6, 0xb5, 0x78, 0xaa,
      0x70, 0xe5, 0x58, 0x20, 0x4e, 0x34, 0x42, 0x77, 0x08, 0x27, 0x11,
   };

   Crypto_DataBlob keyBlob = {
      .data = reinterpret_cast<uint8_t *>(pubKeyText),
      .len = sizeof(pubKeyText)
   };

   uint8_t signText[] = {
      0x30, 0x45, 0x02, 0x21, 0x00, 0xf4, 0xe7, 0x9d, 0x35, 0x33, 0xa6, 0x86, 0x2e, 0x2a, 0x97, 0x72,
      0xc9, 0x46, 0x79, 0x65, 0xca, 0x4a, 0x71, 0x34, 0xca, 0xf7, 0x58, 0xb3, 0x26, 0xa5, 0xdb, 0xfa,
      0x8b, 0xbe, 0xbf, 0x5f, 0x90, 0x02, 0x20, 0x53, 0xb4, 0x23, 0xb1, 0xe2, 0x8f, 0x2f, 0xe9, 0xc8,
      0x22, 0xef, 0xab, 0x9b, 0x13, 0x08, 0x75, 0x8e, 0xb1, 0x9c, 0x59, 0xe5, 0xd6, 0x64, 0x35, 0xf5,
      0xd1, 0xde, 0xfa, 0xfe, 0x80, 0x37, 0x1a,
   };

   Crypto_DataBlob signBlob = {
      .data = reinterpret_cast<uint8_t *>(signText),
      .len = sizeof(signText)
   };
   
   // keypair
   OH_Crypto_ErrCode ret = CRYPTO_SUCCESS;
   ret = OH_CryptoAsymKeyGenerator_Create((const char *)"SM2_256", &keyCtx);
   if (ret != CRYPTO_SUCCESS) {
      return false;
   }
   ret = OH_CryptoAsymKeyGenerator_Convert(keyCtx, CRYPTO_DER, &keyBlob, nullptr, &keyPair);
   if (ret != CRYPTO_SUCCESS) {
      OH_CryptoAsymKeyGenerator_Destroy(keyCtx);
      return false;
   }
   OH_CryptoPubKey *pubKey = OH_CryptoKeyPair_GetPubKey(keyPair);
   // verify
   ret = OH_CryptoVerify_Create((const char *)"SM2_256|SM3", &verify);
   if (ret != CRYPTO_SUCCESS) {
      OH_CryptoVerify_Destroy(verify);
      OH_CryptoAsymKeyGenerator_Destroy(keyCtx);
      return false;
   }
   ret = OH_CryptoVerify_Init(verify, pubKey);
   if (ret != CRYPTO_SUCCESS) {
      OH_CryptoVerify_Destroy(verify);
      OH_CryptoAsymKeyGenerator_Destroy(keyCtx);
      return false;
   }
   bool res = OH_CryptoVerify_Final(verify, &msgBlob, &signBlob);
   if (res != true) {
      OH_CryptoVerify_Destroy(verify);
      OH_CryptoAsymKeyGenerator_Destroy(keyCtx);
      return false;
   }

   OH_CryptoVerify_Destroy(verify);
   OH_CryptoAsymKeyGenerator_Destroy(keyCtx);
   OH_CryptoKeyPair_Destroy(keyPair);
   return res;
}
  ```