AES加解密算法在Android中的应用及Android4.2以上版本调用问题

 from://http://blog.csdn.net/xinzheng_wang/article/details/9159969

AES加解密算法在Android中的应用及Android4.2以上版本调用问题

分类： Android2013-06-24 11:25 328人阅读 评论(3) 收藏 举报

　　

　　密码学中的高级加密标准（Advanced Encryption Standard，AES），又称高级加密标准Rijndael加密法，是美国联邦政府采用的一种区块加密标准。这个标准用来替代原先的DES，已经被多方分析且广为全世界所使用。该算法为比利时密码学家Joan Daemen和Vincent Rijmen所设计，结合两位作者的名字，以Rijndael之命名之。

 要区别4.2以上版本的调用方法，否则将会出现意想不到的问题。

AESCipher.java

package com.test;

import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

public class AESCipher {
    public static String encrypt(String key, String src) throws Exception {
        byte[] rawKey = getRawKey(key.getBytes());
        byte[] result = encrypt(rawKey, src.getBytes());
        return toHex(result);
    }

    public static String decrypt(String key, String encrypted) throws Exception {
        byte[] rawKey = getRawKey(key.getBytes());
        byte[] enc = toByte(encrypted);
        byte[] result = decrypt(rawKey, enc);
        return new String(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
         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[] key, byte[] src) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(key, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
        byte[] encrypted = cipher.doFinal(src);
        return encrypted;
    }

    private static byte[] decrypt(byte[] key, byte[] encrypted) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(key, "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 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;
    }

    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 final static String HEX = "0123456789ABCDEF";
    private static void appendHex(StringBuffer sb, byte b) {
        sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
    }
}

TestAES.java

package com.test;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class TestAES extends Activity implements OnClickListener {
    private TextView tvTip = null;
    private EditText etKey = null;
    private EditText etStr = null;
    private Button btnEncrypt = null;
    private Button btnDecrypt = null;
    //
    String src = null;
    String key = null;
    String dest = null;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        tvTip = (TextView) findViewById(R.id.tvTip);
        etKey = (EditText) findViewById(R.id.etKey);
        etStr = (EditText) findViewById(R.id.etStr);
        btnEncrypt = (Button) findViewById(R.id.btnEncrypt);
        btnEncrypt.setOnClickListener(this);
        btnDecrypt = (Button) findViewById(R.id.btnDecrypt);
        btnDecrypt.setOnClickListener(this);
        btnEncrypt.setEnabled(true);
        btnDecrypt.setEnabled(false);

    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        if (v == btnEncrypt) {
            src = etStr.getText().toString().trim();
            key = etKey.getText().toString().trim();
            if (!src.equals("") && !key.equals("")) {
                try {
                    dest = AESCipher.encrypt(key, src);
                    tvTip.setText("Encrypted:");
                    etStr.setText(dest);
                    btnEncrypt.setEnabled(false);
                    btnDecrypt.setEnabled(true);
                } catch (Exception e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }

        } else if (v == btnDecrypt) {
            src = etStr.getText().toString().trim();
            key = etKey.getText().toString().trim();
            if (!src.equals("") && !key.equals("")) {
                try {
                    dest = AESCipher.decrypt(key, src);
                    tvTip.setText("Decrypted:");
                    etStr.setText(dest);
                    btnDecrypt.setEnabled(false);
                    btnEncrypt.setEnabled(true);
                } catch (Exception e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }else{
                tvTip.setText("Source:");
                btnDecrypt.setEnabled(false);
                btnEncrypt.setEnabled(true);
            }
        }
    }
}

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical" >

        <TextView
            android:layout_width="100dp"
            android:layout_height="wrap_content"
            android:text="Key：" />

        <EditText
            android:id="@+id/etKey"
            android:layout_width="200dp"
            android:layout_height="40dp"
            android:maxLength="32"
            android:hint="Input the key" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical" >

        <TextView
            android:id="@+id/tvTip"
            android:layout_width="100dp"
            android:layout_height="wrap_content"
            android:text="Source:" />

        <EditText
            android:id="@+id/etStr"
            android:layout_width="400dp"
            android:layout_height="200dp"
            android:hint="Input the source"
            android:inputType="textMultiLine"
            android:maxLength="4096"
            android:maxLines="100"
            android:scrollHorizontally="false" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <Button
            android:id="@+id/btnEncrypt"
            android:layout_width="120dp"
            android:layout_height="50dp"
            android:text="加密字符串" />

        <Button
            android:id="@+id/btnDecrypt"
            android:layout_width="120dp"
            android:layout_height="50dp"
            android:text="解密字符串" />

    </LinearLayout>

</LinearLayout>