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1# 使用SM4对称密钥（CBC模式）加解密(ArkTS)
2
3<!--Kit: Crypto Architecture Kit-->
4<!--Subsystem: Security-->
5<!--Owner: @zxz--3-->
6<!--Designer: @lanming-->
7<!--Tester: @PAFT-->
8<!--Adviser: @zengyawen-->
9
10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)。
11
12**加密**
13
141. 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）。
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.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[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。
19
203. 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。
21
224. 调用[Cipher.update](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#update-1)，更新数据（明文）。
23
24   - 当数据量较小时，可以在init完成后直接调用doFinal。
25   - 当数据量较大时，可以多次调用update，即分段加解密。
26
275. 调用[Cipher.doFinal](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#dofinal-1)，获取加密后的数据。
28
29   - 由于已使用update传入数据，此处data传入null。
30   - 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。
31
32**解密**
33
341. 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。
35
362. 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。
37
383. 调用[Cipher.update](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#update-1)，更新数据（密文）。
39
404. 调用[Cipher.doFinal](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#dofinal-1)，获取解密后的数据。
41
42- 异步方法示例：
43
44  ```ts
45  import { cryptoFramework } from '@kit.CryptoArchitectureKit';
46  import { buffer } from '@kit.ArkTS';
47
48  function generateRandom(len: number) {
49    let rand = cryptoFramework.createRandom();
50    let generateRandSync = rand.generateRandomSync(len);
51    return generateRandSync;
52  }
53
54  function genIvParamsSpec() {
55    let ivBlob = generateRandom(16); // 16 bytes
56    let ivParamsSpec: cryptoFramework.IvParamsSpec = {
57      algName: "IvParamsSpec",
58      iv: ivBlob
59    };
60    return ivParamsSpec;
61  }
62  let iv = genIvParamsSpec();
63  // 加密消息。
64  async function encryptMessagePromise(symKey: cryptoFramework.SymKey, plainText: cryptoFramework.DataBlob) {
65    let cipher = cryptoFramework.createCipher('SM4_128|CBC|PKCS7');
66    await cipher.init(cryptoFramework.CryptoMode.ENCRYPT_MODE, symKey, iv);
67    let encryptData = await cipher.doFinal(plainText);
68    return encryptData;
69  }
70  // 解密消息。
71  async function decryptMessagePromise(symKey: cryptoFramework.SymKey, cipherText: cryptoFramework.DataBlob) {
72    let decoder = cryptoFramework.createCipher('SM4_128|CBC|PKCS7');
73    await decoder.init(cryptoFramework.CryptoMode.DECRYPT_MODE, symKey, iv);
74    let decryptData = await decoder.doFinal(cipherText);
75    return decryptData;
76  }
77  async function genSymKeyByData(symKeyData: Uint8Array) {
78    let symKeyBlob: cryptoFramework.DataBlob = { data: symKeyData };
79    let symGenerator = cryptoFramework.createSymKeyGenerator('SM4_128');
80    let symKey = await symGenerator.convertKey(symKeyBlob);
81    console.info('convertKey success');
82    return symKey;
83  }
84  async function main() {
85    try {
86      let keyData = new Uint8Array([7, 154, 52, 176, 4, 236, 150, 43, 237, 9, 145, 166, 141, 174, 224, 131]);
87      let symKey = await genSymKeyByData(keyData);
88      let message = "This is a test";
89      let plainText: cryptoFramework.DataBlob = { data: new Uint8Array(buffer.from(message, 'utf-8').buffer) };
90      let encryptText = await encryptMessagePromise(symKey, plainText);
91      let decryptText = await decryptMessagePromise(symKey, encryptText);
92      if (plainText.data.toString() === decryptText.data.toString()) {
93        console.info('decrypt ok');
94        console.info('decrypt plainText: ' + buffer.from(decryptText.data).toString('utf-8'));
95      } else {
96        console.error('decrypt failed');
97      }
98    } catch (error) {
99      console.error(`SM4 “${error}“, error code: ${error.code}`);
100    }
101  }
102  ```
103
104- 同步方法示例：
105
106  ```ts
107  import { cryptoFramework } from '@kit.CryptoArchitectureKit';
108  import { buffer } from '@kit.ArkTS';
109
110  function generateRandom(len: number) {
111    let rand = cryptoFramework.createRandom();
112    let generateRandSync = rand.generateRandomSync(len);
113    return generateRandSync;
114  }
115
116  function genIvParamsSpec() {
117    let ivBlob = generateRandom(16); // 16 bytes
118    let ivParamsSpec: cryptoFramework.IvParamsSpec = {
119      algName: "IvParamsSpec",
120      iv: ivBlob
121    };
122    return ivParamsSpec;
123  }
124  let iv = genIvParamsSpec();
125  // 加密消息。
126  function encryptMessage(symKey: cryptoFramework.SymKey, plainText: cryptoFramework.DataBlob) {
127    let cipher = cryptoFramework.createCipher('SM4_128|CBC|PKCS7');
128    cipher.initSync(cryptoFramework.CryptoMode.ENCRYPT_MODE, symKey, iv);
129    let encryptData = cipher.doFinalSync(plainText);
130    return encryptData;
131  }
132  // 解密消息。
133  function decryptMessage(symKey: cryptoFramework.SymKey, cipherText: cryptoFramework.DataBlob) {
134    let decoder = cryptoFramework.createCipher('SM4_128|CBC|PKCS7');
135    decoder.initSync(cryptoFramework.CryptoMode.DECRYPT_MODE, symKey, iv);
136    let decryptData = decoder.doFinalSync(cipherText);
137    return decryptData;
138  }
139  function genSymKeyByData(symKeyData: Uint8Array) {
140    let symKeyBlob: cryptoFramework.DataBlob = { data: symKeyData };
141    let symGenerator = cryptoFramework.createSymKeyGenerator('SM4_128');
142    let symKey = symGenerator.convertKeySync(symKeyBlob);
143    console.info('convertKeySync success');
144    return symKey;
145  }
146  function main() {
147    try {
148      let keyData = new Uint8Array([7, 154, 52, 176, 4, 236, 150, 43, 237, 9, 145, 166, 141, 174, 224, 131]);
149      let symKey = genSymKeyByData(keyData);
150      let message = "This is a test";
151      let plainText: cryptoFramework.DataBlob = { data: new Uint8Array(buffer.from(message, 'utf-8').buffer) };
152      let encryptText = encryptMessage(symKey, plainText);
153      let decryptText = decryptMessage(symKey, encryptText);
154      if (plainText.data.toString() === decryptText.data.toString()) {
155        console.info('decrypt ok');
156        console.info('decrypt plainText: ' + buffer.from(decryptText.data).toString('utf-8'));
157      } else {
158        console.error('decrypt failed');
159      }
160    } catch (error) {
161      console.error(`SM4 “${error}“, error code: ${error.code}`);
162    }
163  }
164  ```