Android AES加密算法及其实现

       昨天老大叫我看看android加密算法。于是网上找了找，找到了AES加密算法。（当然还有MD5,BASE64什么的http://snowolf.iteye.com/blog/379860这篇文章列举了很多，但是基本都是j2se平台的，android平台不一定支持，但是AES算法Android是自带了包的，从官方的http://developer.android.com/reference/javax/crypto/Cipher.html可以看到。
）

 AES加密算法是什么？大家可以自己去google，专家级程序员写好包，工程人员会用就行了。

这个例子其实是来自http://www.tutorials-android.com/learn/How_to_encrypt_and_decrypt_strings.rhtml。

src目录主文件：

package com.qq;
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.util.Log;

public class SimpleCrypto extends Activity {
	 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);    
	    }    
	   
	    private static byte[] getRawKey(byte[] seed) throws Exception {    
	        KeyGenerator kgen = KeyGenerator.getInstance("AES");    
	        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");    
	        sr.setSeed(seed);    
	        kgen.init(128, sr); // 192 and 256 bits may not be available    
	        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 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));    
	    } 
	/** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        String masterPassword = "a";
        String originalText = "0123456789";
        byte[] text = new byte[]{'0','1','2','3','4','5','6','7','8','9'};
        byte[] password = new byte[]{'a'};
        try {
    		String encryptingCode = SimpleCrypto.encrypt(masterPassword,originalText);
//    		System.out.println("加密结果为 " + encryptingCode);
    		Log.i("加密结果为 ",encryptingCode);
    		String decryptingCode = SimpleCrypto.decrypt(masterPassword, encryptingCode);
    		System.out.println("解密结果为 " + decryptingCode);
    		Log.i("解密结果",decryptingCode);
    	   } catch (Exception e) {
    		// TODO Auto-generated catch block
    		e.printStackTrace();
    }
    }
}

运行结果（从log日志中看到的）：

I/加密结果为 (  190): BFB77D8F1E1EE9D5E252926A12659DE8

I/解密结果(  190): 0123456789