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1# 使用SM4对称密钥（CBC模式）加解密(ArkTS)
2
3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)。
4
5**加密**
6
71. 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）。
8
9   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。
10
112. 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，用于完成加密操作。
12
133. 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。
14
154. 调用[Cipher.update](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#update-1)，更新数据（明文）。
16
17   - 当数据量较小时，可以在init完成后直接调用doFinal。
18   - 当数据量较大时，可以多次调用update，即分段加解密。
19
205. 调用[Cipher.doFinal](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#dofinal-1)，获取加密后的数据。
21
22   - 由于已使用update传入数据，此处data传入null。
23   - 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。
24
25**解密**
26
271. 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，用于完成解密操作。
28
292. 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。
30
313. 调用[Cipher.update](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#update-1)，更新数据（密文）。
32
334. 调用[Cipher.doFinal](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#dofinal-1)，获取解密后的数据。
34
35- 异步方法示例：
36
37  ```ts
38  import { cryptoFramework } from '@kit.CryptoArchitectureKit';
39  import { buffer } from '@kit.ArkTS';
40
41  function generateRandom(len: number) {
42    let rand = cryptoFramework.createRandom();
43    let generateRandSync = rand.generateRandomSync(len);
44    return generateRandSync;
45  }
46
47  function genIvParamsSpec() {
48    let ivBlob = generateRandom(16); // 16 bytes
49    let ivParamsSpec: cryptoFramework.IvParamsSpec = {
50      algName: "IvParamsSpec",
51      iv: ivBlob
52    };
53    return ivParamsSpec;
54  }
55  let iv = genIvParamsSpec();
56  // 加密消息。
57  async function encryptMessagePromise(symKey: cryptoFramework.SymKey, plainText: cryptoFramework.DataBlob) {
58    let cipher = cryptoFramework.createCipher('SM4_128|CBC|PKCS7');
59    await cipher.init(cryptoFramework.CryptoMode.ENCRYPT_MODE, symKey, iv);
60    let encryptData = await cipher.doFinal(plainText);
61    return encryptData;
62  }
63  // 解密消息。
64  async function decryptMessagePromise(symKey: cryptoFramework.SymKey, cipherText: cryptoFramework.DataBlob) {
65    let decoder = cryptoFramework.createCipher('SM4_128|CBC|PKCS7');
66    await decoder.init(cryptoFramework.CryptoMode.DECRYPT_MODE, symKey, iv);
67    let decryptData = await decoder.doFinal(cipherText);
68    return decryptData;
69  }
70  async function genSymKeyByData(symKeyData: Uint8Array) {
71    let symKeyBlob: cryptoFramework.DataBlob = { data: symKeyData };
72    let symGenerator = cryptoFramework.createSymKeyGenerator('SM4_128');
73    let symKey = await symGenerator.convertKey(symKeyBlob);
74    console.info('convertKey success');
75    return symKey;
76  }
77  async function main() {
78    try {
79      let keyData = new Uint8Array([7, 154, 52, 176, 4, 236, 150, 43, 237, 9, 145, 166, 141, 174, 224, 131]);
80      let symKey = await genSymKeyByData(keyData);
81      let message = "This is a test";
82      let plainText: cryptoFramework.DataBlob = { data: new Uint8Array(buffer.from(message, 'utf-8').buffer) };
83      let encryptText = await encryptMessagePromise(symKey, plainText);
84      let decryptText = await decryptMessagePromise(symKey, encryptText);
85      if (plainText.data.toString() === decryptText.data.toString()) {
86        console.info('decrypt ok');
87        console.info('decrypt plainText: ' + buffer.from(decryptText.data).toString('utf-8'));
88      } else {
89        console.error('decrypt failed');
90      }
91    } catch (error) {
92      console.error(`SM4 “${error}“, error code: ${error.code}`);
93    }
94  }
95  ```
96
97- 同步方法示例：
98
99  ```ts
100  import { cryptoFramework } from '@kit.CryptoArchitectureKit';
101  import { buffer } from '@kit.ArkTS';
102
103  function generateRandom(len: number) {
104    let rand = cryptoFramework.createRandom();
105    let generateRandSync = rand.generateRandomSync(len);
106    return generateRandSync;
107  }
108
109  function genIvParamsSpec() {
110    let ivBlob = generateRandom(16); // 16 bytes
111    let ivParamsSpec: cryptoFramework.IvParamsSpec = {
112      algName: "IvParamsSpec",
113      iv: ivBlob
114    };
115    return ivParamsSpec;
116  }
117  let iv = genIvParamsSpec();
118  // 加密消息。
119  function encryptMessage(symKey: cryptoFramework.SymKey, plainText: cryptoFramework.DataBlob) {
120    let cipher = cryptoFramework.createCipher('SM4_128|CBC|PKCS7');
121    cipher.initSync(cryptoFramework.CryptoMode.ENCRYPT_MODE, symKey, iv);
122    let encryptData = cipher.doFinalSync(plainText);
123    return encryptData;
124  }
125  // 解密消息。
126  function decryptMessage(symKey: cryptoFramework.SymKey, cipherText: cryptoFramework.DataBlob) {
127    let decoder = cryptoFramework.createCipher('SM4_128|CBC|PKCS7');
128    decoder.initSync(cryptoFramework.CryptoMode.DECRYPT_MODE, symKey, iv);
129    let decryptData = decoder.doFinalSync(cipherText);
130    return decryptData;
131  }
132  function genSymKeyByData(symKeyData: Uint8Array) {
133    let symKeyBlob: cryptoFramework.DataBlob = { data: symKeyData };
134    let symGenerator = cryptoFramework.createSymKeyGenerator('SM4_128');
135    let symKey = symGenerator.convertKeySync(symKeyBlob);
136    console.info('convertKeySync success');
137    return symKey;
138  }
139  function main() {
140    try {
141      let keyData = new Uint8Array([7, 154, 52, 176, 4, 236, 150, 43, 237, 9, 145, 166, 141, 174, 224, 131]);
142      let symKey = genSymKeyByData(keyData);
143      let message = "This is a test";
144      let plainText: cryptoFramework.DataBlob = { data: new Uint8Array(buffer.from(message, 'utf-8').buffer) };
145      let encryptText = encryptMessage(symKey, plainText);
146      let decryptText = decryptMessage(symKey, encryptText);
147      if (plainText.data.toString() === decryptText.data.toString()) {
148        console.info('decrypt ok');
149        console.info('decrypt plainText: ' + buffer.from(decryptText.data).toString('utf-8'));
150      } else {
151        console.error('decrypt failed');
152      }
153    } catch (error) {
154      console.error(`SM4 “${error}“, error code: ${error.code}`);
155    }
156  }
157  ```