1# 使用AES对称密钥（GCM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：AES](crypto-sym-encrypt-decrypt-spec.md#aes)。
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6
7**加密**
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9
101. 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AES、密钥长度为128位的对称密钥（SymKey）。
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12   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.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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142. 调用[cryptoFramework.createCipher](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#cryptoframeworkcreatecipher)，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。
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163. 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GCM模式对应的加密参数（GcmParamsSpec），初始化加密Cipher实例。
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184. 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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20   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。
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22   - 当数据量较小时，可以在init完成后直接调用doFinal。
23   - 当数据量较大时，可以多次调用update，即分段加解密。
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255. 调用[Cipher.doFinal](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#dofinal-1)，获取加密后的数据。
26   - 由于已使用update传入数据，此处data传入null。
27   - 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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296. 读取[GcmParamsSpec](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#gcmparamsspec).authTag作为解密的认证信息。
30   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。
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32
33**解密**
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361. 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GCM模式对应的解密参数（GcmParamsSpec），初始化解密Cipher实例。
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382. 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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403. 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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42
43- 异步方法示例：
44
45  ```ts
46  import { cryptoFramework } from '@kit.CryptoArchitectureKit';
47  import { buffer } from '@kit.ArkTS';
48
49  function generateRandom(len: number) {
50    let rand = cryptoFramework.createRandom();
51    let generateRandSync = rand.generateRandomSync(len);
52    return generateRandSync;
53  }
54
55  function genGcmParamsSpec() {
56    let ivBlob = generateRandom(12);
57    let arr = [1, 2, 3, 4, 5, 6, 7, 8]; // 8 bytes
58    let dataAad = new Uint8Array(arr);
59    let aadBlob: cryptoFramework.DataBlob = { data: dataAad };
60    arr = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]; // 16 bytes
61    let dataTag = new Uint8Array(arr);
62    let tagBlob: cryptoFramework.DataBlob = {
63      data: dataTag
64    };
65    // GCM的authTag在加密时从doFinal结果中获取，在解密时填入init函数的params参数中
66    let gcmParamsSpec: cryptoFramework.GcmParamsSpec = {
67      iv: ivBlob,
68      aad: aadBlob,
69      authTag: tagBlob,
70      algName: "GcmParamsSpec"
71    };
72    return gcmParamsSpec;
73  }
74
75  let gcmParams = genGcmParamsSpec();
76
77  // 加密消息
78  async function encryptMessagePromise(symKey: cryptoFramework.SymKey, plainText: cryptoFramework.DataBlob) {
79    let cipher = cryptoFramework.createCipher('AES128|GCM|PKCS7');
80    await cipher.init(cryptoFramework.CryptoMode.ENCRYPT_MODE, symKey, gcmParams);
81    let encryptUpdate = await cipher.update(plainText);
82    // gcm模式加密doFinal时传入空，获得tag数据，并更新至gcmParams对象中。
83    gcmParams.authTag = await cipher.doFinal(null);
84    return encryptUpdate;
85  }
86  // 解密消息
87  async function decryptMessagePromise(symKey: cryptoFramework.SymKey, cipherText: cryptoFramework.DataBlob) {
88    let decoder = cryptoFramework.createCipher('AES128|GCM|PKCS7');
89    await decoder.init(cryptoFramework.CryptoMode.DECRYPT_MODE, symKey, gcmParams);
90    let decryptUpdate = await decoder.update(cipherText);
91    // gcm模式解密doFinal时传入空，验证init时传入的tag数据，如果验证失败会抛出异常。
92    let decryptData = await decoder.doFinal(null);
93    if (decryptData == null) {
94      console.info('GCM decrypt success, decryptData is null');
95    }
96    return decryptUpdate;
97  }
98  async function genSymKeyByData(symKeyData: Uint8Array) {
99    let symKeyBlob: cryptoFramework.DataBlob = { data: symKeyData };
100    let aesGenerator = cryptoFramework.createSymKeyGenerator('AES128');
101    let symKey = await aesGenerator.convertKey(symKeyBlob);
102    console.info('convertKey success');
103    return symKey;
104  }
105  async function main() {
106    let keyData = new Uint8Array([83, 217, 231, 76, 28, 113, 23, 219, 250, 71, 209, 210, 205, 97, 32, 159]);
107    let symKey = await genSymKeyByData(keyData);
108    let message = "This is a test";
109    let plainText: cryptoFramework.DataBlob = { data: new Uint8Array(buffer.from(message, 'utf-8').buffer) };
110    let encryptText = await encryptMessagePromise(symKey, plainText);
111    let decryptText = await decryptMessagePromise(symKey, encryptText);
112    if (plainText.data.toString() === decryptText.data.toString()) {
113      console.info('decrypt ok');
114      console.info('decrypt plainText: ' + buffer.from(decryptText.data).toString('utf-8'));
115    } else {
116      console.error('decrypt failed');
117    }
118  }
119  ```
120
121- 同步方法示例：
122
123  ```ts
124  import { cryptoFramework } from '@kit.CryptoArchitectureKit';
125  import { buffer } from '@kit.ArkTS';
126
127  function generateRandom(len: number) {
128    let rand = cryptoFramework.createRandom();
129    let generateRandSync = rand.generateRandomSync(len);
130    return generateRandSync;
131  }
132
133  function genGcmParamsSpec() {
134    let ivBlob = generateRandom(12);
135    let arr = [1, 2, 3, 4, 5, 6, 7, 8]; // 8 bytes
136    let dataAad = new Uint8Array(arr);
137    let aadBlob: cryptoFramework.DataBlob = { data: dataAad };
138    arr = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]; // 16 bytes
139    let dataTag = new Uint8Array(arr);
140    let tagBlob: cryptoFramework.DataBlob = {
141      data: dataTag
142    };
143    // GCM的authTag在加密时从doFinal结果中获取，在解密时填入init函数的params参数中
144    let gcmParamsSpec: cryptoFramework.GcmParamsSpec = {
145      iv: ivBlob,
146      aad: aadBlob,
147      authTag: tagBlob,
148      algName: "GcmParamsSpec"
149    };
150    return gcmParamsSpec;
151  }
152
153  let gcmParams = genGcmParamsSpec();
154
155  // 加密消息
156  function encryptMessage(symKey: cryptoFramework.SymKey, plainText: cryptoFramework.DataBlob) {
157    let cipher = cryptoFramework.createCipher('AES128|GCM|PKCS7');
158    cipher.initSync(cryptoFramework.CryptoMode.ENCRYPT_MODE, symKey, gcmParams);
159    let encryptUpdate = cipher.updateSync(plainText);
160    // gcm模式加密doFinal时传入空，获得tag数据，并更新至gcmParams对象中。
161    gcmParams.authTag = cipher.doFinalSync(null);
162    return encryptUpdate;
163  }
164  // 解密消息
165  function decryptMessage(symKey: cryptoFramework.SymKey, cipherText: cryptoFramework.DataBlob) {
166    let decoder = cryptoFramework.createCipher('AES128|GCM|PKCS7');
167    decoder.initSync(cryptoFramework.CryptoMode.DECRYPT_MODE, symKey, gcmParams);
168    let decryptUpdate = decoder.updateSync(cipherText);
169    // gcm模式解密doFinal时传入空，验证init时传入的tag数据，如果验证失败会抛出异常。
170    let decryptData = decoder.doFinalSync(null);
171    if (decryptData == null) {
172      console.info('GCM decrypt success, decryptData is null');
173    }
174    return decryptUpdate;
175  }
176  function genSymKeyByData(symKeyData: Uint8Array) {
177    let symKeyBlob: cryptoFramework.DataBlob = { data: symKeyData };
178    let aesGenerator = cryptoFramework.createSymKeyGenerator('AES128');
179    let symKey = aesGenerator.convertKeySync(symKeyBlob);
180    console.info('convertKeySync success');
181    return symKey;
182  }
183  function main() {
184    let keyData = new Uint8Array([83, 217, 231, 76, 28, 113, 23, 219, 250, 71, 209, 210, 205, 97, 32, 159]);
185    let symKey = genSymKeyByData(keyData);
186    let message = "This is a test";
187    let plainText: cryptoFramework.DataBlob = { data: new Uint8Array(buffer.from(message, 'utf-8').buffer) };
188    let encryptText = encryptMessage(symKey, plainText);
189    let decryptText = decryptMessage(symKey, encryptText);
190    if (plainText.data.toString() === decryptText.data.toString()) {
191      console.info('decrypt ok');
192      console.info('decrypt plainText: ' + buffer.from(decryptText.data).toString('utf-8'));
193    } else {
194      console.error('decrypt failed');
195    }
196  }
197  ```