1# 使用SM4对称密钥（CBC模式）加解密(ArkTS)
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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)。
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6**加密**
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8
91. 调用[cryptoFramework.createSymKeyGenerator](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#cryptoframeworkcreatesymkeygenerator)、[SymKeyGenerator.generateSymKey](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#generatesymkey-1)，生成密钥算法为SM4、密钥长度为128位的对称密钥（SymKey）。
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11   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.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。
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132. 调用[cryptoFramework.createCipher](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#cryptoframeworkcreatecipher)，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。
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153. 调用[Cipher.init](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#init-1)，设置模式为加密（CryptoMode.ENCRYPT_MODE），指定加密密钥（SymKey）和CBC模式对应的加密参数（IvParamsSpec），初始化加密Cipher实例。
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174. 调用[Cipher.update](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#update-1)，更新数据（明文）。
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19   - 当数据量较小时，可以在init完成后直接调用doFinal。
20   - 当数据量较大时，可以多次调用update，即分段加解密。
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225. 调用[Cipher.doFinal](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#dofinal-1)，获取加密后的数据。
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24   - 由于已使用update传入数据，此处data传入null。
25   - doFinal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。
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27
28**解密**
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311. 调用[Cipher.init](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#init-1)，设置模式为解密（CryptoMode.DECRYPT_MODE），指定解密密钥（SymKey）和CBC模式对应的解密参数（IvParamsSpec），初始化解密Cipher实例。
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332. 调用[Cipher.update](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#update-1)，更新数据（密文）。
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353. 调用[Cipher.doFinal](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#dofinal-1)，获取解密后的数据。
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37
38- 异步方法示例：
39
40  ```ts
41  import { cryptoFramework } from '@kit.CryptoArchitectureKit';
42  import { buffer } from '@kit.ArkTS';
43
44  function generateRandom(len: number) {
45    let rand = cryptoFramework.createRandom();
46    let generateRandSync = rand.generateRandomSync(len);
47    return generateRandSync;
48  }
49
50  function genIvParamsSpec() {
51    let ivBlob = generateRandom(16); // 16 bytes
52    let ivParamsSpec: cryptoFramework.IvParamsSpec = {
53      algName: "IvParamsSpec",
54      iv: ivBlob
55    };
56    return ivParamsSpec;
57  }
58  let iv = genIvParamsSpec();
59  // 加密消息
60  async function encryptMessagePromise(symKey: cryptoFramework.SymKey, plainText: cryptoFramework.DataBlob) {
61    let cipher = cryptoFramework.createCipher('SM4_128|CBC|PKCS7');
62    await cipher.init(cryptoFramework.CryptoMode.ENCRYPT_MODE, symKey, iv);
63    let encryptData = await cipher.doFinal(plainText);
64    return encryptData;
65  }
66  // 解密消息
67  async function decryptMessagePromise(symKey: cryptoFramework.SymKey, cipherText: cryptoFramework.DataBlob) {
68    let decoder = cryptoFramework.createCipher('SM4_128|CBC|PKCS7');
69    await decoder.init(cryptoFramework.CryptoMode.DECRYPT_MODE, symKey, iv);
70    let decryptData = await decoder.doFinal(cipherText);
71    return decryptData;
72  }
73  async function genSymKeyByData(symKeyData: Uint8Array) {
74    let symKeyBlob: cryptoFramework.DataBlob = { data: symKeyData };
75    let symGenerator = cryptoFramework.createSymKeyGenerator('SM4_128');
76    let symKey = await symGenerator.convertKey(symKeyBlob);
77    console.info('convertKey success');
78    return symKey;
79  }
80  async function main() {
81    try {
82      let keyData = new Uint8Array([7, 154, 52, 176, 4, 236, 150, 43, 237, 9, 145, 166, 141, 174, 224, 131]);
83      let symKey = await genSymKeyByData(keyData);
84      let message = "This is a test";
85      let plainText: cryptoFramework.DataBlob = { data: new Uint8Array(buffer.from(message, 'utf-8').buffer) };
86      let encryptText = await encryptMessagePromise(symKey, plainText);
87      let decryptText = await decryptMessagePromise(symKey, encryptText);
88      if (plainText.data.toString() === decryptText.data.toString()) {
89        console.info('decrypt ok');
90        console.info('decrypt plainText: ' + buffer.from(decryptText.data).toString('utf-8'));
91      } else {
92        console.error('decrypt failed');
93      }
94    } catch (error) {
95      console.error(`SM4 “${error}“, error code: ${error.code}`);
96    }
97  }
98  ```
99
100- 同步方法示例：
101
102  ```ts
103  import { cryptoFramework } from '@kit.CryptoArchitectureKit';
104  import { buffer } from '@kit.ArkTS';
105
106  function generateRandom(len: number) {
107    let rand = cryptoFramework.createRandom();
108    let generateRandSync = rand.generateRandomSync(len);
109    return generateRandSync;
110  }
111
112  function genIvParamsSpec() {
113    let ivBlob = generateRandom(16); // 16 bytes
114    let ivParamsSpec: cryptoFramework.IvParamsSpec = {
115      algName: "IvParamsSpec",
116      iv: ivBlob
117    };
118    return ivParamsSpec;
119  }
120  let iv = genIvParamsSpec();
121  // 加密消息
122  function encryptMessage(symKey: cryptoFramework.SymKey, plainText: cryptoFramework.DataBlob) {
123    let cipher = cryptoFramework.createCipher('SM4_128|CBC|PKCS7');
124    cipher.initSync(cryptoFramework.CryptoMode.ENCRYPT_MODE, symKey, iv);
125    let encryptData = cipher.doFinalSync(plainText);
126    return encryptData;
127  }
128  // 解密消息
129  function decryptMessage(symKey: cryptoFramework.SymKey, cipherText: cryptoFramework.DataBlob) {
130    let decoder = cryptoFramework.createCipher('SM4_128|CBC|PKCS7');
131    decoder.initSync(cryptoFramework.CryptoMode.DECRYPT_MODE, symKey, iv);
132    let decryptData = decoder.doFinalSync(cipherText);
133    return decryptData;
134  }
135  function genSymKeyByData(symKeyData: Uint8Array) {
136    let symKeyBlob: cryptoFramework.DataBlob = { data: symKeyData };
137    let symGenerator = cryptoFramework.createSymKeyGenerator('SM4_128');
138    let symKey = symGenerator.convertKeySync(symKeyBlob);
139    console.info('convertKeySync success');
140    return symKey;
141  }
142  function main() {
143    try {
144      let keyData = new Uint8Array([7, 154, 52, 176, 4, 236, 150, 43, 237, 9, 145, 166, 141, 174, 224, 131]);
145      let symKey = genSymKeyByData(keyData);
146      let message = "This is a test";
147      let plainText: cryptoFramework.DataBlob = { data: new Uint8Array(buffer.from(message, 'utf-8').buffer) };
148      let encryptText = encryptMessage(symKey, plainText);
149      let decryptText = decryptMessage(symKey, encryptText);
150      if (plainText.data.toString() === decryptText.data.toString()) {
151        console.info('decrypt ok');
152        console.info('decrypt plainText: ' + buffer.from(decryptText.data).toString('utf-8'));
153      } else {
154        console.error('decrypt failed');
155      }
156    } catch (error) {
157      console.error(`SM4 “${error}“, error code: ${error.code}`);
158    }
159  }
160  ```