小白成长记-----关于Android AES 加解密中的那些问题

来源：互联网发布：新农村频道网络直播编辑：程序博客网时间：2024/06/11 17:22

在网上看了很多关于AES解密的案例、代码，都没有解决加密后无法解密的问题，最后在一个很小很小的角落中找到了答案，学习之余也给大家分享一下。

废话不多说直接上代码。

import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import android.app.Activity;
import android.os.Bundle;
import android.widget.Toast;

public class MainActivity extends Activity {
   private final static String HEX = "0123456789ABCDEF";

    public static String encrypt(String seed, String cleartext) throws Exception {
        byte[] rawKey = getRawKey(seed.getBytes());
        byte[] result = encrypt(rawKey, cleartext.getBytes());
        return toHex(result);
    }

    public static String decrypt(String seed, String encrypted) throws Exception {
        byte[] rawKey = getRawKey(seed.getBytes());
        byte[] enc = toByte(encrypted);
        byte[] result = decrypt(rawKey, enc);
        return new String(result);
    }

    public static byte[] toByte(String hexString) {
        int len = hexString.length() / 2;
        byte[] result = new byte[len];
        for (int i = 0; i < len; i++)
            result[i] = Integer.valueOf(hexString.substring(2 * i, 2 * i + 2), 16).byteValue();
        return result;
    }

    private static byte[] getRawKey(byte[] seed) throws Exception {
       KeyGenerator kgen = KeyGenerator.getInstance("AES");
         // SHA1PRNG 强随机种子算法, 要区别4.2以上版本的调用方法如果不判断4.2版本以上无法解密
          SecureRandom sr = null;
        if (android.os.Build.VERSION.SDK_INT >= 17) {
          sr = SecureRandom.getInstance("SHA1PRNG", "Crypto");
        } else {
          sr = SecureRandom.getInstance("SHA1PRNG");
        }
         sr.setSeed(seed);
         kgen.init(256, sr); //256 bits or 128 bits,192bits
         SecretKey skey = kgen.generateKey();
         byte[] raw = skey.getEncoded();
         return raw;
     }

    private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
        byte[] encrypted = cipher.doFinal(clear);
        return encrypted;
    }

    private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.DECRYPT_MODE, skeySpec);
        byte[] decrypted = cipher.doFinal(encrypted);
        return decrypted;
    }

    public static String toHex(String txt) {
        return toHex(txt.getBytes());
    }

    public static String fromHex(String hex) {
        return new String(toByte(hex));
    }

    public static String toHex(byte[] buf) {
        if (buf == null)
            return "";
        StringBuffer result = new StringBuffer(2 * buf.length);
        for (int i = 0; i < buf.length; i++) {
            appendHex(result, buf[i]);
        }
        return result.toString();
    }

    private static void appendHex(StringBuffer sb, byte b) {
        sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
    }
   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);
       String masterPassword = "a";
        String originalText = "0123456789";
        try {
            System.out.println("加密文本为" + originalText);
            String encryptingCode = MainActivity.encrypt(masterPassword, originalText);
            System.out.println("加密结果为 " + encryptingCode);
            Toast.makeText(this, encryptingCode, 0).show();
            String decryptingCode = MainActivity.decrypt(masterPassword, encryptingCode);
            System.out.println("解密结果为 " + decryptingCode);
            Toast.makeText(this, decryptingCode, 0).show();
        } catch (Exception e) {

            e.printStackTrace();
        }
    }
    ｝

可以看到我的代码中多了一个版本判断，这样在4.2以上的版本就可以完美解密了。

新手勿喷，谢谢

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