如何实现SM4加解密工具
============

#### 问题现象

如何实现一个SM4加解密工具，例如其中入参symAlgName的值为SM4\_128，symKeyData的长度是32位，请提供一个SM4加解密Demo。

#### 背景知识

*   在数据存储或传输场景中，可以使用加解密操作用于保证数据的机密性，防止敏感数据泄露，加解密开发可参考[加解密开发指导](https://developer.huawei.com/consumer/cn/doc/harmonyos-guides/crypto-encrypt-decrypt-dev)。
*   [算法库](https://developer.huawei.com/consumer/cn/doc/harmonyos-guides/crypto-sym-encrypt-decrypt-spec)当前提供了[SM4加解密](https://developer.huawei.com/consumer/cn/doc/harmonyos-guides/crypto-sym-encrypt-decrypt-spec#sm4)常用的7种加密模式：ECB、CBC、CTR、OFB、CFB、CFB128和GCM。
*   由于SM4为分组加密算法，分组长度为128位。在实际应用中，最后一组明文可能不足128位（16字节），此时可以通过不同的填充模式进行数据填充。

#### 解决方案

import { cryptoFramework } from '@kit.CryptoArchitectureKit';
import { buffer } from '@kit.ArkTS';

@Entry
@Component
struct Index {
  build() {
    Column({ space: 30 }) {
      Text('SM4加密')
        .fontSize(50)
        .fontWeight(FontWeight.Bold)
        .onClick(async () \=\> {
          const symAlgName \= 'SM4\_128';
          const sKey: string \= '9f35eda67432c4ae3892305801b9d0b6';
          const symKeyData \= buffer.from(sKey, 'hex');
          let symKeyBlob: cryptoFramework.DataBlob \= { data: new Uint8Array(symKeyData.buffer) };
          try {
            let aesGenerator \= cryptoFramework.createSymKeyGenerator(symAlgName);
            let symKey \= await aesGenerator.convertKey(symKeyBlob);
            console.info(\`wsf: sm4 转密钥成功\`);
            let plainText: cryptoFramework.DataBlob \=
              { data: new Uint8Array(buffer.from('This is a test', 'utf-8').buffer) };
            const cipher \= cryptoFramework.createCipher('SM4\_128|ECB|PKCS7');
            await cipher.init(cryptoFramework.CryptoMode.ENCRYPT\_MODE, symKey, null);
            const encryptData \= await cipher.doFinal(plainText);
            if (encryptData){
              console.info(\`wsf: 加密成功\`);
            }
          } catch (e) {
            console.error(\`wsf: 转密钥报错 e = ${e.code} ${e.message}\`);
          }
        })
      Text('SM4解密')
        .fontSize(50)
        .fontWeight(FontWeight.Bold)
        .onClick(async () \=\> {
          const symAlgName \= 'SM4\_128';
          const sKey: string \= '9f35eda67432c4ae3892305801b9d0b6';
          const symKeyData \= buffer.from(sKey, 'hex');
          let symKeyBlob: cryptoFramework.DataBlob \= { data: new Uint8Array(symKeyData.buffer) };
          try {
            let aesGenerator \= cryptoFramework.createSymKeyGenerator(symAlgName);
            let symKey \= await aesGenerator.convertKey(symKeyBlob);
            let arr \= \[186, 255, 20, 91, 43, 218, 215, 77, 185, 100, 22, 186, 42, 178, 121, 45\];
            let dataAad \= new Uint8Array(arr);
            let encryptData: cryptoFramework.DataBlob \= { data: dataAad };
            let decoder \= cryptoFramework.createCipher('SM4\_128|ECB|PKCS7');
            await decoder.init(cryptoFramework.CryptoMode.DECRYPT\_MODE, symKey, null);
            let decryptData \= await decoder.doFinal(encryptData);
            console.info(\`wsf: 解密成功 ${buffer.from(decryptData.data).toString()}\`);
          } catch (e) {
            console.error(\`wsf: 转密钥报错 e = ${e.code} ${e.message}\`);
          }
        })
    }
    .height('100%')
    .width('100%')
  }
}