# 使用RC4对称密钥加解密(ArkTS)

从API版本26.0.0开始，算法库支持RC4对称密钥加解密。

对应的算法规格请参见对称密钥加解密算法规格：RC4。

RC4为流密码算法，无需分组模式与填充。

**加密**

1.  调用cryptoFramework.createSymKeyGenerator、SymKeyGenerator.generateSymKey或SymKeyGenerator.convertKey，生成密钥算法为RC4、密钥长度在8位～4096位范围内（如RC4\_128）的对称密钥（SymKey）。
    
    如何生成RC4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：RC4和指定二进制数据转换对称密钥理解，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。
    
2.  调用cryptoFramework.createCipher，指定字符串参数（如'RC4'），创建对称密钥类型为RC4的Cipher实例，用于完成加密操作。
    
3.  调用Cipher.init，设置模式为加密（cryptoFramework.CryptoMode.ENCRYPT\_MODE），指定加密密钥（SymKey），初始化加密Cipher实例。RC4为流密码，无IV等加解密参数时传入null。
    
4.  当加密内容长度较短时，可以直接调用 Cipher.doFinal 而无需调用update，以获取加密后的数据。
    

**解密**

1.  调用cryptoFramework.createCipher，指定字符串参数（如'RC4'），创建对称密钥类型为RC4的Cipher实例，用于完成解密操作。
    
2.  调用Cipher.init，设置模式为解密（cryptoFramework.CryptoMode.DECRYPT\_MODE），指定解密密钥（SymKey）初始化解密Cipher实例。无加解密参数时传入null。
    
3.  当解密内容长度较短时，可以省略调用update，直接调用Cipher.doFinal，获取解密后的数据。
    

*   异步方法示例：
    
    ```
    import { cryptoFramework } from '@kit.CryptoArchitectureKit';
    import { buffer } from '@kit.ArkTS';
    
    
    // 加密消息
    async function encryptMessagePromise(symKey: cryptoFramework.SymKey, plainText: cryptoFramework.DataBlob) {
      let cipher = cryptoFramework.createCipher('RC4');
      await cipher.init(cryptoFramework.CryptoMode.ENCRYPT_MODE, symKey, null);
      let cipherData = await cipher.doFinal(plainText);
      return cipherData;
    }
    
    // 解密消息
    async function decryptMessagePromise(symKey: cryptoFramework.SymKey, cipherText: cryptoFramework.DataBlob) {
      let decoder = cryptoFramework.createCipher('RC4');
      await decoder.init(cryptoFramework.CryptoMode.DECRYPT_MODE, symKey, null);
      let decryptData = await decoder.doFinal(cipherText);
      return decryptData;
    }
    
    async function genSymKeyByData(symKeyData: Uint8Array) {
      let symKeyBlob: cryptoFramework.DataBlob = { data: symKeyData };
      let rc4Generator = cryptoFramework.createSymKeyGenerator('RC4');
      let symKey = await rc4Generator.convertKey(symKeyBlob);
      console.info('convertKey result: success.');
      return symKey;
    }
    
    async function rc4EncryptionDecryption() {
      let keyData = new Uint8Array([83, 217, 231, 76, 28, 113, 23, 219, 250, 71, 209, 210, 205, 97, 32, 159]);
      let symKey = await genSymKeyByData(keyData);
      let message = 'This is a test';
      let plainText: cryptoFramework.DataBlob = { data: new Uint8Array(buffer.from(message, 'utf-8').buffer) };
      let encryptText = await encryptMessagePromise(symKey, plainText);
      let decryptText = await decryptMessagePromise(symKey, encryptText);
      if (plainText.data.toString() === decryptText.data.toString()) {
        console.info('decrypt ok.');
        console.info('decrypt plainText: ' + buffer.from(decryptText.data).toString('utf-8'));
      } else {
        console.error('decrypt failed.');
      }
    }
    ```
    
*   同步方法示例：
    
    ```
    import { cryptoFramework } from '@kit.CryptoArchitectureKit';
    import { buffer } from '@kit.ArkTS';
    
    
    // 加密消息
    function encryptMessage(symKey: cryptoFramework.SymKey, plainText: cryptoFramework.DataBlob) {
      let cipher = cryptoFramework.createCipher('RC4');
      cipher.initSync(cryptoFramework.CryptoMode.ENCRYPT_MODE, symKey, null);
      let cipherData = cipher.doFinalSync(plainText);
      return cipherData;
    }
    
    // 解密消息
    function decryptMessage(symKey: cryptoFramework.SymKey, cipherText: cryptoFramework.DataBlob) {
      let decoder = cryptoFramework.createCipher('RC4');
      decoder.initSync(cryptoFramework.CryptoMode.DECRYPT_MODE, symKey, null);
      let decryptData = decoder.doFinalSync(cipherText);
      return decryptData;
    }
    
    function genSymKeyByData(symKeyData: Uint8Array) {
      let symKeyBlob: cryptoFramework.DataBlob = { data: symKeyData };
      let rc4Generator = cryptoFramework.createSymKeyGenerator('RC4');
      let symKey = rc4Generator.convertKeySync(symKeyBlob);
      console.info('convertKeySync result: success.');
      return symKey;
    }
    
    function rc4EncryptionDecryption() {
      let keyData = new Uint8Array([83, 217, 231, 76, 28, 113, 23, 219, 250, 71, 209, 210, 205, 97, 32, 159]);
      let symKey = genSymKeyByData(keyData);
      let message = 'This is a test';
      let plainText: cryptoFramework.DataBlob = { data: new Uint8Array(buffer.from(message, 'utf-8').buffer) };
      let encryptText = encryptMessage(symKey, plainText);
      let decryptText = decryptMessage(symKey, encryptText);
      if (plainText.data.toString() === decryptText.data.toString()) {
        console.info('decrypt ok.');
        console.info('decrypt plainText: ' + buffer.from(decryptText.data).toString('utf-8'));
      } else {
        console.error('decrypt failed.');
      }
    }
    ```