1# 使用SM4对称密钥(CBC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:SM4](crypto-sym-encrypt-decrypt-spec.md#sm4)。 5 6## 在CMake脚本中链接相关动态库 7```txt 8 target_link_libraries(entry PUBLIC libohcrypto.so) 9``` 10 11**加密** 12 13 141. 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SM4、密钥长度为128位的对称密钥(OH_CryptoSymKey)。 15 16 如何生成SM4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:SM4](crypto-sym-key-generation-conversion-spec.md#sm4)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。 17 182. 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'SM4_128|CBC|PKCS7',创建对称密钥类型为SM4_128、分组模式为CBC、填充模式为PKCS7的Cipher实例,用于完成加解密操作。 19 203. 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。 21 224. 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CBC模式对应的加密参数(OH_CryptoSymCipherParams),初始化加密Cipher实例。 23 245. 调用[OH_CryptoSymCipher_Update](../../reference/apis-crypto-architecture-kit/_crypto_sym_cipher_api.md#oh_cryptosymcipher_update),更新数据(明文)。 25 26 - 当数据量较小时,可以在init完成后直接调用final。 27 - 当数据量较大时,可以多次调用update,即分段加解密。 28 296. 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。 30 31 - 由于已使用update传入数据,此处data传入null。 32 - 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。 33 347. 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。 35 36 37**解密** 38 39 401. 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CBC模式对应的解密参数(OH_CryptoSymCipherParams),初始化解密Cipher实例。 41 422. 调用[OH_CryptoSymCipher_Update](../../reference/apis-crypto-architecture-kit/_crypto_sym_cipher_api.md#oh_cryptosymcipher_update),更新数据(密文)。 43 443. 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。 45 46 47 48```c++ 49#include "CryptoArchitectureKit/crypto_common.h" 50#include "CryptoArchitectureKit/crypto_sym_cipher.h" 51#include <string.h> 52 53static OH_Crypto_ErrCode doTestSm4Cbc() 54{ 55 OH_CryptoSymKeyGenerator *genCtx = nullptr; 56 OH_CryptoSymCipher *encCtx = nullptr; 57 OH_CryptoSymCipher *decCtx = nullptr; 58 OH_CryptoSymKey *keyCtx = nullptr; 59 OH_CryptoSymCipherParams *params = nullptr; 60 Crypto_DataBlob outUpdate = {.data = nullptr, .len = 0}; 61 Crypto_DataBlob decUpdate = {.data = nullptr, .len = 0}; 62 63 char *plainText = const_cast<char *>("this is test!"); 64 Crypto_DataBlob msgBlob = {.data = (uint8_t *)(plainText), .len = strlen(plainText)}; 65 uint8_t iv[16] = {1, 2, 4, 12, 3, 4, 2, 3, 3, 2, 0, 4, 3, 1, 0, 10}; // iv使用安全随机数生成 66 Crypto_DataBlob ivBlob = {.data = iv, .len = sizeof(iv)}; 67 // 生成对称密钥 68 OH_Crypto_ErrCode ret; 69 ret = OH_CryptoSymKeyGenerator_Create("SM4_128", &genCtx); 70 if (ret != CRYPTO_SUCCESS) { 71 goto end; 72 } 73 ret = OH_CryptoSymKeyGenerator_Generate(genCtx, &keyCtx); 74 if (ret != CRYPTO_SUCCESS) { 75 goto end; 76 } 77 78 // 设置参数 79 ret = OH_CryptoSymCipherParams_Create(¶ms); 80 if (ret != CRYPTO_SUCCESS) { 81 goto end; 82 } 83 ret = OH_CryptoSymCipherParams_SetParam(params, CRYPTO_IV_DATABLOB, &ivBlob); 84 if (ret != CRYPTO_SUCCESS) { 85 goto end; 86 } 87 88 // 加密 89 ret = OH_CryptoSymCipher_Create("SM4_128|CBC|PKCS7", &encCtx); 90 if (ret != CRYPTO_SUCCESS) { 91 goto end; 92 } 93 ret = OH_CryptoSymCipher_Init(encCtx, CRYPTO_ENCRYPT_MODE, keyCtx, params); 94 if (ret != CRYPTO_SUCCESS) { 95 goto end; 96 } 97 ret = OH_CryptoSymCipher_Final(encCtx, &msgBlob, &outUpdate); 98 if (ret != CRYPTO_SUCCESS) { 99 goto end; 100 } 101 102 // 解密 103 ret = OH_CryptoSymCipher_Create("SM4_128|CBC|PKCS7", &decCtx); 104 if (ret != CRYPTO_SUCCESS) { 105 goto end; 106 } 107 ret = OH_CryptoSymCipher_Init(decCtx, CRYPTO_DECRYPT_MODE, keyCtx, params); 108 if (ret != CRYPTO_SUCCESS) { 109 goto end; 110 } 111 ret = OH_CryptoSymCipher_Final(decCtx, &outUpdate, &decUpdate); 112 if (ret != CRYPTO_SUCCESS) { 113 goto end; 114 } 115 116 // 资源释放 117end: 118 OH_CryptoSymCipherParams_Destroy(params); 119 OH_CryptoSymCipher_Destroy(encCtx); 120 OH_CryptoSymCipher_Destroy(decCtx); 121 OH_CryptoSymKeyGenerator_Destroy(genCtx); 122 OH_CryptoSymKey_Destroy(keyCtx); 123 OH_Crypto_FreeDataBlob(&outUpdate); 124 OH_Crypto_FreeDataBlob(&decUpdate); 125 return ret; 126} 127```