1# Signature Verification with an RSA Key Pair (PKCS1 Mode) (C/C++)
2
3
4For details about the algorithm specifications, see [RSA](crypto-sign-sig-verify-overview.md#rsa).
5
6
7## Adding the Dynamic Library in the CMake Script
8```txt
9   target_link_libraries(entry PUBLIC libohcrypto.so)
10```
11
12## How to Develop
13
14
151. Use [OH_CryptoVerify_Create](../../reference/apis-crypto-architecture-kit/_crypto_signature_api.md#oh_cryptoverify_create) with the string parameter **'RSA1024|PKCS1|SHA256'** to create a **Verify** instance. The string parameter must be the same as that used to create the **Sign** instance.
16
172. Use [OH_CryptoVerify_Init](../../reference/apis-crypto-architecture-kit/_crypto_signature_api.md#oh_cryptoverify_init) to initialize the **Verify** instance by using the public key (**OH_CryptoPubKey**).
18
193. Use [OH_CryptoVerify_Update](../../reference/apis-crypto-architecture-kit/_crypto_signature_api.md#oh_cryptoverify_update) to pass in the data to be verified.
20
21   Currently, the amount of data to be passed in by a single **OH_CryptoVerify_Update** is not limited. You can determine how to pass in data based on the data volume.
22
23   - If a small amount of data is to be verified, you can directly call [OH_CryptoVerify_Final](../../reference/apis-crypto-architecture-kit/_crypto_signature_api.md#oh_cryptoverify_final) after **OH_CryptoVerify_Init()**.
24   - If a large amount of data is to be verified, call **OH_CryptoVerify_Update()** multiple times to [pass in data by segment](crypto-rsa-sign-sig-verify-pkcs1-by-segment-ndk.md).
25
264. Use [OH_CryptoVerify_Final](../../reference/apis-crypto-architecture-kit/_crypto_signature_api.md#oh_cryptoverify_final) to verify the signature.
27
28
29**Example**
30
31```c++
32#include "CryptoArchitectureKit/crypto_common.h"
33#include "CryptoArchitectureKit/crypto_asy_key.h"
34
35static bool doTestRsaSignature()
36{
37   OH_CryptoAsymKeyGenerator *keyCtx = nullptr;
38   OH_CryptoKeyPair *keyPair = nullptr;
39   OH_CryptoVerify *verify = nullptr;
40
41   uint8_t plainText[] = {
42      0x43, 0x31, 0x7d, 0xb5, 0x85, 0x2e, 0xd4, 0xef, 0x08, 0x7a, 0x17, 0x96, 0xbc, 0x7c, 0x8f, 0x80,
43      0x8c, 0xa7, 0x63, 0x7f, 0x26, 0x89, 0x8f, 0xf0, 0xfa, 0xa7, 0x51, 0xbd, 0x9c, 0x69, 0x17, 0xf3,
44      0xd1, 0xb5, 0xc7, 0x12, 0xbf, 0xcf, 0x91, 0x25, 0x82, 0x23, 0x6b, 0xd6, 0x64, 0x52, 0x77, 0x93,
45      0x01, 0x9d, 0x70, 0xa3, 0xf4, 0x92, 0x16, 0xec, 0x3f, 0xa7, 0x3c, 0x83, 0x8d, 0x40, 0x41, 0xfc,
46   };
47   Crypto_DataBlob msgBlob = {
48      .data = reinterpret_cast<uint8_t *>(plainText),
49      .len = sizeof(plainText)
50   };
51
52   uint8_t pubKeyText[] = {
53      0x2d, 0x2d, 0x2d, 0x2d, 0x2d, 0x42, 0x45, 0x47, 0x49, 0x4e, 0x20, 0x52, 0x53, 0x41, 0x20, 0x50,
54      0x55, 0x42, 0x4c, 0x49, 0x43, 0x20, 0x4b, 0x45, 0x59, 0x2d, 0x2d, 0x2d, 0x2d, 0x2d, 0x0a, 0x4d,
55      0x49, 0x47, 0x4a, 0x41, 0x6f, 0x47, 0x42, 0x41, 0x4d, 0x78, 0x63, 0x44, 0x4d, 0x6f, 0x61, 0x59,
56      0x52, 0x58, 0x6f, 0x78, 0x65, 0x69, 0x33, 0x49, 0x6d, 0x33, 0x33, 0x78, 0x4a, 0x76, 0x61, 0x73,
57      0x63, 0x43, 0x62, 0x77, 0x31, 0x6f, 0x73, 0x63, 0x32, 0x56, 0x56, 0x69, 0x47, 0x6a, 0x56, 0x47,
58      0x47, 0x4a, 0x37, 0x6c, 0x75, 0x4e, 0x41, 0x58, 0x6b, 0x6a, 0x73, 0x56, 0x46, 0x64, 0x35, 0x0a,
59      0x58, 0x37, 0x4c, 0x4d, 0x6c, 0x46, 0x34, 0x63, 0x35, 0x5a, 0x75, 0x59, 0x2f, 0x61, 0x69, 0x57,
60      0x77, 0x70, 0x54, 0x69, 0x63, 0x62, 0x67, 0x49, 0x33, 0x43, 0x66, 0x50, 0x6f, 0x32, 0x6a, 0x6c,
61      0x52, 0x74, 0x67, 0x41, 0x46, 0x6b, 0x44, 0x71, 0x7a, 0x4b, 0x53, 0x46, 0x62, 0x46, 0x47, 0x51,
62      0x6b, 0x43, 0x6e, 0x64, 0x63, 0x2b, 0x54, 0x59, 0x6b, 0x5a, 0x42, 0x32, 0x70, 0x45, 0x6f, 0x72,
63      0x0a, 0x7a, 0x73, 0x61, 0x56, 0x58, 0x77, 0x5a, 0x47, 0x45, 0x34, 0x41, 0x43, 0x70, 0x59, 0x35,
64      0x79, 0x65, 0x66, 0x49, 0x44, 0x6c, 0x45, 0x57, 0x49, 0x51, 0x4f, 0x6a, 0x59, 0x4b, 0x2f, 0x6c,
65      0x58, 0x71, 0x7a, 0x48, 0x47, 0x69, 0x4f, 0x69, 0x32, 0x75, 0x4a, 0x45, 0x75, 0x44, 0x43, 0x50,
66      0x6a, 0x51, 0x64, 0x6a, 0x54, 0x41, 0x67, 0x4d, 0x42, 0x41, 0x41, 0x45, 0x3d, 0x0a, 0x2d, 0x2d,
67      0x2d, 0x2d, 0x2d, 0x45, 0x4e, 0x44, 0x20, 0x52, 0x53, 0x41, 0x20, 0x50, 0x55, 0x42, 0x4c, 0x49,
68      0x43, 0x20, 0x4b, 0x45, 0x59, 0x2d, 0x2d, 0x2d, 0x2d, 0x2d, 0x0a,
69   };
70
71   Crypto_DataBlob keyBlob = {
72      .data = reinterpret_cast<uint8_t *>(pubKeyText),
73      .len = sizeof(pubKeyText)
74   };
75
76   uint8_t signText[] = {
77      0x68, 0x2f, 0x3b, 0xe6, 0xa6, 0x5c, 0xb8, 0x60, 0xd4, 0xe1, 0x64, 0xa7, 0xd8, 0x0c, 0x9c, 0x89,
78      0x39, 0xb4, 0xf0, 0xb7, 0xad, 0xb5, 0x8a, 0x71, 0x04, 0xf1, 0xa5, 0x63, 0xdd, 0x32, 0x6a, 0x44,
79      0xeb, 0xff, 0xb7, 0xe6, 0x85, 0xe5, 0xa5, 0x55, 0x5d, 0x5b, 0x28, 0x53, 0x63, 0xe4, 0xb3, 0xb9,
80      0xa8, 0x70, 0xc8, 0x8f, 0xcd, 0x21, 0x8d, 0xe6, 0x1f, 0xe5, 0x78, 0x34, 0xd3, 0x45, 0x0c, 0x9c,
81      0x7a, 0x22, 0x1b, 0x63, 0x55, 0xca, 0x14, 0xa5, 0x0c, 0x7a, 0x40, 0x8e, 0xa1, 0x14, 0x78, 0xa1,
82      0xf1, 0x36, 0x78, 0xbd, 0xba, 0x37, 0x3b, 0x5b, 0xb0, 0x8e, 0xb3, 0x4a, 0x9b, 0x1b, 0x0c, 0xfa,
83      0xfa, 0xc7, 0x9f, 0xb1, 0x35, 0x48, 0x82, 0x73, 0xf8, 0x6b, 0xd4, 0x76, 0x33, 0x5c, 0xed, 0x9c,
84      0xd8, 0x4b, 0xc9, 0x92, 0xa0, 0x3f, 0x6e, 0xba, 0x78, 0x2e, 0x80, 0x78, 0x1e, 0x74, 0xa0, 0x47,
85   };
86
87   Crypto_DataBlob signBlob = {
88      .data = reinterpret_cast<uint8_t *>(signText),
89      .len = sizeof(signText)
90   };
91
92   // keypair
93   OH_Crypto_ErrCode ret = CRYPTO_SUCCESS;
94   ret = OH_CryptoAsymKeyGenerator_Create((const char *)"RSA2048", &keyCtx);
95   if (ret != CRYPTO_SUCCESS) {
96      return false;
97   }
98   ret = OH_CryptoAsymKeyGenerator_Convert(keyCtx, CRYPTO_PEM, &keyBlob, nullptr, &keyPair);
99   if (ret != CRYPTO_SUCCESS) {
100      OH_CryptoAsymKeyGenerator_Destroy(keyCtx);
101      return false;
102   }
103   OH_CryptoPubKey *pubKey = OH_CryptoKeyPair_GetPubKey(keyPair);
104   // verify
105   ret = OH_CryptoVerify_Create((const char *)"RSA1024|PKCS1|SHA256", &verify);
106   if (ret != CRYPTO_SUCCESS) {
107      OH_CryptoVerify_Destroy(verify);
108      OH_CryptoAsymKeyGenerator_Destroy(keyCtx);
109      return false;
110   }
111   ret = OH_CryptoVerify_Init(verify, pubKey);
112   if (ret != CRYPTO_SUCCESS) {
113      OH_CryptoVerify_Destroy(verify);
114      OH_CryptoAsymKeyGenerator_Destroy(keyCtx);
115      return false;
116   }
117   bool res = OH_CryptoVerify_Final(verify, &msgBlob, &signBlob);
118   if (res != true) {
119      OH_CryptoVerify_Destroy(verify);
120      OH_CryptoAsymKeyGenerator_Destroy(keyCtx);
121      return false;
122   }
123
124   OH_CryptoVerify_Destroy(verify);
125   OH_CryptoAsymKeyGenerator_Destroy(keyCtx);
126   OH_CryptoKeyPair_Destroy(keyPair);
127   return res;
128}
129```
130