Android AES加密算法及其实现

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();
     }
     }
 }

布局文件main.xml和配置文件AndroidManifest.xml默认就好了。最后结果在Log里面看，利用adb logcat > d:\1.txt定位到D盘的1.txt文件，然后用记事本打开就，查找”加密结果为“就可以看到了：

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