1# HMAC (C/C++)
2
3
4A Hash-based Message Authentication Code (HMAC) is a specific type of message authentication code (MAC) involving a cryptographic has function and a secret cryptographic key. For details about the scenarios and supported algorithm specifications, see [HMAC Overview and Algorithm Specifications](huks-hmac-overview.md).
5
6## Add the dynamic library in the CMake script.
7```txt
8   target_link_libraries(entry PUBLIC libhuks_ndk.z.so)
9```
10
11## How to Develop
12
13**Key Generation**
14
151. Set the key alias.
16
172. Initialize the key property set.
18
193. Use [OH_Huks_GenerateKeyItem](../../reference/apis-universal-keystore-kit/_huks_key_api.md#oh_huks_generatekeyitem) to generate a key. For details about the HMAC specifications, see [Key Generation](huks-key-generation-overview.md#supported-algorithms).
20
21You can also import a key. For details about the supported algorithms, see [Supported Algorithms](huks-key-import-overview.md#supported-algorithms).
22
23**HMAC Generation**
24
251. Obtain the key alias.
26
272. Obtains the data to be calculated.
28
293. Use [OH_Huks_InitParamSet](../../reference/apis-universal-keystore-kit/_huks_param_set_api.md#oh_huks_initparamset) to configure algorithm parameters.
30
31
324. Use [OH_Huks_InitSession](../../reference/apis-universal-keystore-kit/_huks_key_api.md#oh_huks_initsession) to initialize a key session. The session handle is returned after the initialization.
33
345. Use [OH_Huks_FinishSession](../../reference/apis-universal-keystore-kit/_huks_key_api.md#oh_huks_finishsession) to obtain the hashed data.
35
36```c++
37#include "huks/native_huks_api.h"
38#include "huks/native_huks_param.h"
39#include <string.h>
40OH_Huks_Result InitParamSet(
41    struct OH_Huks_ParamSet **paramSet,
42    const struct OH_Huks_Param *params,
43    uint32_t paramCount)
44{
45    OH_Huks_Result ret = OH_Huks_InitParamSet(paramSet);
46    if (ret.errorCode != OH_HUKS_SUCCESS) {
47        return ret;
48    }
49    ret = OH_Huks_AddParams(*paramSet, params, paramCount);
50    if (ret.errorCode != OH_HUKS_SUCCESS) {
51        OH_Huks_FreeParamSet(paramSet);
52        return ret;
53    }
54    ret = OH_Huks_BuildParamSet(paramSet);
55    if (ret.errorCode != OH_HUKS_SUCCESS) {
56        OH_Huks_FreeParamSet(paramSet);
57        return ret;
58    }
59    return ret;
60}
61
62static struct OH_Huks_Param g_genHmacParams[] = {
63    {
64        .tag = OH_HUKS_TAG_ALGORITHM,
65        .uint32Param = OH_HUKS_ALG_HMAC
66    }, {
67        .tag = OH_HUKS_TAG_PURPOSE,
68        .uint32Param = OH_HUKS_KEY_PURPOSE_MAC
69    }, {
70        .tag = OH_HUKS_TAG_KEY_SIZE,
71        .uint32Param = OH_HUKS_AES_KEY_SIZE_256
72    }, {
73        .tag = OH_HUKS_TAG_DIGEST,
74        .uint32Param = OH_HUKS_DIGEST_SHA384
75    }
76};
77
78static const uint32_t HMAC_COMMON_SIZE = 1024;
79OH_Huks_Result HksHmacTest(
80        const struct OH_Huks_Blob *keyAlias,
81        const struct OH_Huks_ParamSet *hmacParamSet, const struct OH_Huks_Blob *inData, struct OH_Huks_Blob *hashText)
82{
83    uint8_t handleE[sizeof(uint64_t)] = {0};
84    struct OH_Huks_Blob handle = {sizeof(uint64_t), handleE};
85    OH_Huks_Result ret = OH_Huks_InitSession(keyAlias, hmacParamSet, &handle, nullptr);
86    if (ret.errorCode != OH_HUKS_SUCCESS) {
87        return ret;
88    }
89    ret = OH_Huks_FinishSession(&handle, hmacParamSet, inData, hashText);
90    return ret;
91}
92
93static napi_value HmacKey(napi_env env, napi_callback_info info)
94{
95    /* 1. Generate Key */
96    /*
97    * Simulate the key generation scenario.
98    * 1.1. Set the key alias.
99    */
100    char tmpKeyAlias[] = "test_hmac";
101    struct OH_Huks_Blob keyAlias = { (uint32_t)strlen(tmpKeyAlias), (uint8_t *)tmpKeyAlias };
102    struct OH_Huks_ParamSet *hmacParamSet = nullptr;
103    OH_Huks_Result ohResult;
104    do {
105        /*
106        * 1.2. Obtain the parameters for key generation.
107        */
108        ohResult = InitParamSet(&hmacParamSet, g_genHmacParams, sizeof(g_genHmacParams) / sizeof(OH_Huks_Param));
109        if (ohResult.errorCode != OH_HUKS_SUCCESS) {
110            break;
111        }
112        /*
113        * 1.3. Call generateKeyItem to generate a key.
114        */
115        ohResult = OH_Huks_GenerateKeyItem(&keyAlias, hmacParamSet, nullptr);
116        if (ohResult.errorCode != OH_HUKS_SUCCESS) {
117            break;
118        }
119        /* 2. HMAC */
120        /*
121        * Simulate a hash scenario.
122        * 2.1. Obtain the key alias.
123        */
124        /*
125        * 2.2. Obtain the data to be hashed.
126        */
127        char tmpInData[] = "HMAC_MAC_INDATA_1";
128        struct OH_Huks_Blob inData = { (uint32_t)strlen(tmpInData), (uint8_t *)tmpInData };
129        uint8_t cipher[HMAC_COMMON_SIZE] = {0};
130        struct OH_Huks_Blob hashText = {HMAC_COMMON_SIZE, cipher};
131        /*
132        * 2.3. Call initSession to obtain a session handle.
133        */
134        /*
135        * 2.4. Call finishSession to obtain the hashed data.
136        */
137        ohResult = HksHmacTest(&keyAlias, hmacParamSet, &inData, &hashText);
138        if (ohResult.errorCode != OH_HUKS_SUCCESS) {
139            break;
140        }
141    } while (0);
142    OH_Huks_FreeParamSet(&hmacParamSet);
143}
144```
145