1# 使用AES对称密钥(GCM模式)加解密(C/C++) 2 3 4对应的算法规格请查看[对称密钥加解密算法规格:AES](crypto-sym-encrypt-decrypt-spec.md#aes)。 5 6 7## 在CMake脚本中链接相关动态库 8```txt 9 target_link_libraries(entry PUBLIC libohcrypto.so) 10``` 11 12## 开发步骤 13 14**加密** 15 16 171. 调用[OH_CryptoSymKeyGenerator_Create](../../reference/apis-crypto-architecture-kit/_crypto_sym_key_api.md#oh_cryptosymkeygenerator_create)、[OH_CryptoSymKeyGenerator_Generate](../../reference/apis-crypto-architecture-kit/_crypto_sym_key_api.md#oh_cryptosymkeygenerator_generate),生成密钥算法为AES、密钥长度为128位的对称密钥(OH_CryptoSymKey)。 18 19 如何生成AES对称密钥,开发者可参考下文示例,并结合[对称密钥生成和转换规格:AES](crypto-sym-key-generation-conversion-spec.md#aes)和[随机生成对称密钥](crypto-generate-sym-key-randomly-ndk.md)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。 20 212. 调用[OH_CryptoSymCipher_Create](../../reference/apis-crypto-architecture-kit/_crypto_sym_cipher_api.md#oh_cryptosymcipher_create),指定字符串参数'AES128|GCM|PKCS7',创建对称密钥类型为AES128、分组模式为GCM、填充模式为PKCS7的Cipher实例,用于完成加解密操作。 22 233. 调用[OH_CryptoSymCipherParams_Create](../../reference/apis-crypto-architecture-kit/_crypto_sym_cipher_api.md#oh_cryptosymcipherparams_create)创建参数对象,调用[OH_CryptoSymCipherParams_SetParam](../../reference/apis-crypto-architecture-kit/_crypto_sym_cipher_api.md#oh_cryptosymcipherparams_setparam)设置对应的加密参数。 24 254. 调用[OH_CryptoSymCipher_Init](../../reference/apis-crypto-architecture-kit/_crypto_sym_cipher_api.md#oh_cryptosymcipher_init),设置模式为加密(CRYPTO_ENCRYPT_MODE),指定加密密钥(OH_CryptoSymKey)和GCM模式对应的加密参数(OH_CryptoSymCipherParams),初始化加密Cipher实例。 26 275. 调用[OH_CryptoSymCipher_Update](../../reference/apis-crypto-architecture-kit/_crypto_sym_cipher_api.md#oh_cryptosymcipher_update),更新数据(明文)。 28 29 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。 30 31 - 当数据量较小时,可以在init完成后直接调用final。 32 - 当数据量较大时,可以多次调用update,即分段加解密。 33 346. 调用[OH_CryptoSymCipher_Final](../../reference/apis-crypto-architecture-kit/_crypto_sym_cipher_api.md#oh_cryptosymcipher_final),获取加密后的数据。 35 - 由于已使用update传入数据,此处data传入null。 36 - 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。 37 387. 使用[OH_CryptoSymCipherParams_Create](../../reference/apis-crypto-architecture-kit/_crypto_sym_cipher_api.md#oh_cryptosymcipherparams_create)创建Params,使用[OH_CryptoSymCipherParams_SetParam](../../reference/apis-crypto-architecture-kit/_crypto_sym_cipher_api.md#oh_cryptosymcipherparams_setparam)设置authTag,作为解密的认证信息。 39 在GCM模式下,需要从加密后的数据中取出末尾16字节,作为解密时初始化的认证信息。示例中authTag恰好为16字节。 40 418. 调用[OH_CryptoSymKeyGenerator_Destroy](../../reference/apis-crypto-architecture-kit/_crypto_sym_key_api.md#oh_cryptosymkeygenerator_destroy)、[OH_CryptoSymCipher_Destroy](../../reference/apis-crypto-architecture-kit/_crypto_sym_cipher_api.md#oh_cryptosymcipher_destroy)、[OH_CryptoSymCipherParams_Destroy](../../reference/apis-crypto-architecture-kit/_crypto_sym_cipher_api.md#oh_cryptosymcipherparams_destroy)销毁各对象。 42 43 44**解密** 45 46 471. 调用[OH_CryptoSymCipher_Init](../../reference/apis-crypto-architecture-kit/_crypto_sym_cipher_api.md#oh_cryptosymcipher_init),设置模式为解密(CRYPTO_DECRYPT_MODE),指定解密密钥(OH_CryptoSymKey)和GCM模式对应的解密参数(OH_CryptoSymCipherParams),初始化解密Cipher实例。 48 492. 调用[OH_CryptoSymCipher_Update](../../reference/apis-crypto-architecture-kit/_crypto_sym_cipher_api.md#oh_cryptosymcipher_update),更新数据(密文)。 50 513. 调用[OH_CryptoSymCipher_Final](../../reference/apis-crypto-architecture-kit/_crypto_sym_cipher_api.md#oh_cryptosymcipher_final),获取解密后的数据。 52 53 54- AES GCM模式加解密示例如下: 55 56```c++ 57#include "CryptoArchitectureKit/crypto_common.h" 58#include "CryptoArchitectureKit/crypto_sym_cipher.h" 59#include <string.h> 60 61static OH_Crypto_ErrCode doTestAesGcm() 62{ 63 OH_CryptoSymKeyGenerator *genCtx = nullptr; 64 OH_CryptoSymCipher *encCtx = nullptr; 65 OH_CryptoSymCipher *decCtx = nullptr; 66 OH_CryptoSymKey *keyCtx = nullptr; 67 OH_CryptoSymCipherParams *params = nullptr; 68 69 Crypto_DataBlob outUpdate = {.data = nullptr, .len = 0}; 70 Crypto_DataBlob decUpdate = {.data = nullptr, .len = 0}; 71 72 uint8_t aad[8] = {1, 2, 3, 4, 5, 6, 7, 8}; 73 uint8_t tag[16] = {0}; 74 uint8_t iv[12] = {1, 2, 4, 12, 3, 4, 2, 3, 3, 2, 0, 4}; // iv使用安全随机数生成 75 Crypto_DataBlob ivData = {.data = iv, .len = sizeof(iv)}; 76 Crypto_DataBlob aadData = {.data = aad, .len = sizeof(aad)}; 77 Crypto_DataBlob tagData = {.data = tag, .len = sizeof(tag)}; 78 Crypto_DataBlob tagOutPut = {.data = nullptr, .len = 0}; 79 char *plainText = const_cast<char *>("this is test!"); 80 Crypto_DataBlob msgBlob = {.data = (uint8_t *)(plainText), .len = strlen(plainText)}; 81 82 // 生成对称密钥 83 OH_Crypto_ErrCode ret; 84 ret = OH_CryptoSymKeyGenerator_Create("AES128", &genCtx); 85 if (ret != CRYPTO_SUCCESS) { 86 goto end; 87 } 88 ret = OH_CryptoSymKeyGenerator_Generate(genCtx, &keyCtx); 89 if (ret != CRYPTO_SUCCESS) { 90 goto end; 91 } 92 93 // 设置参数 94 ret = OH_CryptoSymCipherParams_Create(¶ms); 95 if (ret != CRYPTO_SUCCESS) { 96 goto end; 97 } 98 ret = OH_CryptoSymCipherParams_SetParam(params, CRYPTO_IV_DATABLOB, &ivData); 99 if (ret != CRYPTO_SUCCESS) { 100 goto end; 101 } 102 ret = OH_CryptoSymCipherParams_SetParam(params, CRYPTO_AAD_DATABLOB, &aadData); 103 if (ret != CRYPTO_SUCCESS) { 104 goto end; 105 } 106 ret = OH_CryptoSymCipherParams_SetParam(params, CRYPTO_TAG_DATABLOB, &tagData); 107 if (ret != CRYPTO_SUCCESS) { 108 goto end; 109 } 110 111 // 加密 112 ret = OH_CryptoSymCipher_Create("AES128|GCM|PKCS7", &encCtx); 113 if (ret != CRYPTO_SUCCESS) { 114 goto end; 115 } 116 ret = OH_CryptoSymCipher_Init(encCtx, CRYPTO_ENCRYPT_MODE, keyCtx, params); 117 if (ret != CRYPTO_SUCCESS) { 118 goto end; 119 } 120 ret = OH_CryptoSymCipher_Update(encCtx, &msgBlob, &outUpdate); 121 if (ret != CRYPTO_SUCCESS) { 122 goto end; 123 } 124 ret = OH_CryptoSymCipher_Final(encCtx, nullptr, &tagOutPut); 125 if (ret != CRYPTO_SUCCESS) { 126 goto end; 127 } 128 129 // 解密 130 ret = OH_CryptoSymCipher_Create("AES128|GCM|PKCS7", &decCtx); 131 if (ret != CRYPTO_SUCCESS) { 132 goto end; 133 } 134 ret = OH_CryptoSymCipherParams_SetParam(params, CRYPTO_TAG_DATABLOB, &tagOutPut); 135 if (ret != CRYPTO_SUCCESS) { 136 goto end; 137 } 138 ret = OH_CryptoSymCipher_Init(decCtx, CRYPTO_DECRYPT_MODE, keyCtx, params); 139 if (ret != CRYPTO_SUCCESS) { 140 goto end; 141 } 142 ret = OH_CryptoSymCipher_Final(decCtx, &outUpdate, &decUpdate); 143 if (ret != CRYPTO_SUCCESS) { 144 goto end; 145 } 146 147end: 148 OH_CryptoSymCipherParams_Destroy(params); 149 OH_CryptoSymCipher_Destroy(encCtx); 150 OH_CryptoSymCipher_Destroy(decCtx); 151 OH_CryptoSymKeyGenerator_Destroy(genCtx); 152 OH_CryptoSymKey_Destroy(keyCtx); 153 OH_Crypto_FreeDataBlob(&outUpdate); 154 OH_Crypto_FreeDataBlob(&decUpdate); 155 OH_Crypto_FreeDataBlob(&tagOutPut); 156 return ret; 157} 158```