1# 使用RSA非对称密钥分段加解密
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4对应的算法规格请查看[非对称密钥加解密算法规格：RSA](crypto-asym-encrypt-decrypt-spec.md#rsa)。
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7**加密**
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101. 调用[cryptoFramework.createAsyKeyGenerator](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#cryptoframeworkcreateasykeygenerator)、[AsyKeyGenerator.generateKeyPair](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#generatekeypair-1)，生成RSA密钥类型为RSA1024、素数个数为2（不填默认）的非对称密钥对（KeyPair）。KeyPair对象中包括公钥PubKey、私钥PriKey。
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12   如何生成RSA非对称密钥对，开发者可参考下文示例，并结合[非对称密钥生成和转换规格：RSA](crypto-asym-key-generation-conversion-spec.md#rsa)和[随机生成非对称密钥对](crypto-generate-asym-key-pair-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'RSA1024|PKCS1'，创建非对称密钥类型为RSA1024、填充模式为PKCS1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（KeyPair.PubKey），初始化加密Cipher实例。
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184. 多次调用[Cipher.doFinal](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#dofinal-1)，传入明文，获取加密后的数据。
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20   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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22   此处将明文按64个字节一组拆分，多次加密。使用1024位密钥，每次将生成128字节密文。
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25**解密**
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281. 由于RSA算法的Cipher实例不支持重复init操作，需要调用[cryptoFramework.createCipher](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#cryptoframeworkcreatecipher)，重新生成Cipher实例。
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302. 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（KeyPair.PriKey）初始化解密Cipher实例。PKCS1模式无加密参数，直接传入null。
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323. 多次调用[Cipher.doFinal](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#dofinal-1)，传入密文，获取解密后的数据。
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34
35- 异步方法示例：
36
37  ```ts
38  import { cryptoFramework } from '@kit.CryptoArchitectureKit';
39  import { buffer } from '@kit.ArkTS';
40  // 分段加密消息
41  async function rsaEncryptBySegment(pubKey: cryptoFramework.PubKey, plainText: cryptoFramework.DataBlob) {
42    let cipher = cryptoFramework.createCipher('RSA1024|PKCS1');
43    await cipher.init(cryptoFramework.CryptoMode.ENCRYPT_MODE, pubKey, null);
44    let plainTextSplitLen = 64;
45    let cipherText = new Uint8Array();
46    for (let i = 0; i < plainText.data.length; i += plainTextSplitLen ) {
47      let updateMessage = plainText.data.subarray(i, i + plainTextSplitLen );
48      let updateMessageBlob: cryptoFramework.DataBlob = { data: updateMessage };
49      // 将原文按64字符进行拆分，循环调用doFinal进行加密，使用1024bit密钥时，每次加密生成128字节长度的密文
50      let updateOutput = await cipher.doFinal(updateMessageBlob);
51      let mergeText = new Uint8Array(cipherText.length + updateOutput.data.length);
52      mergeText.set(cipherText);
53      mergeText.set(updateOutput.data, cipherText.length);
54      cipherText = mergeText;
55    }
56    let cipherBlob: cryptoFramework.DataBlob = { data: cipherText };
57    return cipherBlob;
58  }
59  // 分段解密消息
60  async function rsaDecryptBySegment(priKey: cryptoFramework.PriKey, cipherText: cryptoFramework.DataBlob) {
61    let decoder = cryptoFramework.createCipher('RSA1024|PKCS1');
62    await decoder.init(cryptoFramework.CryptoMode.DECRYPT_MODE, priKey, null);
63    let cipherTextSplitLen = 128; // RSA密钥每次加密生成的密文字节长度计算方式：密钥位数/8
64    let decryptText = new Uint8Array();
65    for (let i = 0; i < cipherText.data.length; i += cipherTextSplitLen) {
66      let updateMessage = cipherText.data.subarray(i, i + cipherTextSplitLen);
67      let updateMessageBlob: cryptoFramework.DataBlob = { data: updateMessage };
68      // 将密文按128字节进行拆分解密，得到原文后进行拼接
69      let updateOutput = await decoder.doFinal(updateMessageBlob);
70      let mergeText = new Uint8Array(decryptText.length + updateOutput.data.length);
71      mergeText.set(decryptText);
72      mergeText.set(updateOutput.data, decryptText.length);
73      decryptText = mergeText;
74    }
75    let decryptBlob: cryptoFramework.DataBlob = { data: decryptText };
76    return decryptBlob;
77  }
78  async function rsaEncryptLongMessage() {
79    let message = "This is a long plainTest! This is a long plainTest! This is a long plainTest!" +
80      "This is a long plainTest! This is a long plainTest! This is a long plainTest! This is a long plainTest!" +
81      "This is a long plainTest! This is a long plainTest! This is a long plainTest! This is a long plainTest!" +
82      "This is a long plainTest! This is a long plainTest! This is a long plainTest! This is a long plainTest!" +
83      "This is a long plainTest! This is a long plainTest! This is a long plainTest! This is a long plainTest!" +
84      "This is a long plainTest! This is a long plainTest! This is a long plainTest! This is a long plainTest!" +
85      "This is a long plainTest! This is a long plainTest! This is a long plainTest! This is a long plainTest!" +
86      "This is a long plainTest! This is a long plainTest! This is a long plainTest! This is a long plainTest!";
87    let asyKeyGenerator = cryptoFramework.createAsyKeyGenerator("RSA1024"); // 创建非对称密钥生成器对象
88    let keyPair = await asyKeyGenerator.generateKeyPair(); // 随机生成RSA密钥
89    let plainText: cryptoFramework.DataBlob = { data: new Uint8Array(buffer.from(message, 'utf-8').buffer) };
90    let encryptText = await rsaEncryptBySegment(keyPair.pubKey, plainText);
91    let decryptText = await rsaDecryptBySegment(keyPair.priKey, 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  }
99  ```
100
101- 同步方法示例：
102
103  ```ts
104  import { cryptoFramework } from '@kit.CryptoArchitectureKit';
105  import { buffer } from '@kit.ArkTS';
106  // 分段加密消息
107  function rsaEncryptBySegment(pubKey: cryptoFramework.PubKey, plainText: cryptoFramework.DataBlob) {
108    let cipher = cryptoFramework.createCipher('RSA1024|PKCS1');
109    cipher.initSync(cryptoFramework.CryptoMode.ENCRYPT_MODE, pubKey, null);
110    let plainTextSplitLen = 64;
111    let cipherText = new Uint8Array();
112    for (let i = 0; i < plainText.data.length; i += plainTextSplitLen ) {
113      let updateMessage = plainText.data.subarray(i, i + plainTextSplitLen );
114      let updateMessageBlob: cryptoFramework.DataBlob = { data: updateMessage };
115      // 将原文按64字符进行拆分，循环调用doFinal进行加密，使用1024bit密钥时，每次加密生成128字节长度的密文
116      let updateOutput = cipher.doFinalSync(updateMessageBlob);
117      let mergeText = new Uint8Array(cipherText.length + updateOutput.data.length);
118      mergeText.set(cipherText);
119      mergeText.set(updateOutput.data, cipherText.length);
120      cipherText = mergeText;
121    }
122    let cipherBlob: cryptoFramework.DataBlob = { data: cipherText };
123    return cipherBlob;
124  }
125  // 分段解密消息
126  function rsaDecryptBySegment(priKey: cryptoFramework.PriKey, cipherText: cryptoFramework.DataBlob) {
127    let decoder = cryptoFramework.createCipher('RSA1024|PKCS1');
128    decoder.initSync(cryptoFramework.CryptoMode.DECRYPT_MODE, priKey, null);
129    let cipherTextSplitLen = 128; // RSA密钥每次加密生成的密文字节长度计算方式：密钥位数/8
130    let decryptText = new Uint8Array();
131    for (let i = 0; i < cipherText.data.length; i += cipherTextSplitLen) {
132      let updateMessage = cipherText.data.subarray(i, i + cipherTextSplitLen);
133      let updateMessageBlob: cryptoFramework.DataBlob = { data: updateMessage };
134      // 将密文按128字节进行拆分解密，得到原文后进行拼接
135      let updateOutput = decoder.doFinalSync(updateMessageBlob);
136      let mergeText = new Uint8Array(decryptText.length + updateOutput.data.length);
137      mergeText.set(decryptText);
138      mergeText.set(updateOutput.data, decryptText.length);
139      decryptText = mergeText;
140    }
141    let decryptBlob: cryptoFramework.DataBlob = { data: decryptText };
142    return decryptBlob;
143  }
144  function main() {
145    let message = "This is a long plainTest! This is a long plainTest! This is a long plainTest!" +
146      "This is a long plainTest! This is a long plainTest! This is a long plainTest! This is a long plainTest!" +
147      "This is a long plainTest! This is a long plainTest! This is a long plainTest! This is a long plainTest!" +
148      "This is a long plainTest! This is a long plainTest! This is a long plainTest! This is a long plainTest!" +
149      "This is a long plainTest! This is a long plainTest! This is a long plainTest! This is a long plainTest!" +
150      "This is a long plainTest! This is a long plainTest! This is a long plainTest! This is a long plainTest!" +
151      "This is a long plainTest! This is a long plainTest! This is a long plainTest! This is a long plainTest!" +
152      "This is a long plainTest! This is a long plainTest! This is a long plainTest! This is a long plainTest!";
153    let asyKeyGenerator = cryptoFramework.createAsyKeyGenerator("RSA1024"); // 创建非对称密钥生成器对象
154    let keyPair = asyKeyGenerator.generateKeyPairSync(); // 随机生成RSA密钥
155    let plainText: cryptoFramework.DataBlob = { data: new Uint8Array(buffer.from(message, 'utf-8').buffer) };
156    let encryptText = rsaEncryptBySegment(keyPair.pubKey, plainText);
157    let decryptText = rsaDecryptBySegment(keyPair.priKey, encryptText);
158    if (plainText.data.toString() === decryptText.data.toString()) {
159      console.info('decrypt ok');
160      console.info('decrypt plainText: ' + buffer.from(decryptText.data).toString('utf-8'));
161    } else {
162      console.error('decrypt failed');
163    }
164  }
165  ```