使用AES加密进行Android的SharedPreferences存储

1.概述
SharedPreferences是Android提供用来存储一些简单配置信息的机制，其以KEY-VALUE对的方式进行存储，以便我们可以方便进行读取和存储。主要可以用来存储应用程序的欢迎语、常量参数或登录账号密码等。
2.实例
（1）创建项目SharedPreferencesDemo项目

（2）编辑主界面的布局文件main.xml如下：

[xhtml] view plain copy

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="SharedPreferences，是Android提供用来存储一些简单的配置信息的一种机制。"
    />
    <EditText android:layout_height="wrap_content" android:layout_width="fill_parent" android:id="@+id/edtAccount" android:text=""></EditText>
    <EditText android:layout_height="wrap_content" android:layout_width="fill_parent" android:id="@+id/edtPassword" android:text=""></EditText>
    <Button android:text="清空" android:id="@+id/btnClear" android:layout_width="fill_parent" android:layout_height="wrap_content">    </Button>
    <Button android:text="退出" android:id="@+id/btnExit" android:layout_width="fill_parent" android:layout_height="wrap_content"></Button>
</LinearLayout>

（3）创建AES加解密工具类AESEncryptor.java
其中主要提供加密encrypt、解密decrypt两个方法。（AES加解密算法具体大家可以到网上搜索相关资料）
以下为该类文件的源码：
[java] view plain copy

package ni.demo.sharedpreferences;
import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
/**
* AES加密器
* @author Eric_Ni
*
*/
public class AESEncryptor {
    /**
     * AES加密
     */
    public static String encrypt(String seed, String cleartext) throws Exception {
        byte[] rawKey = getRawKey(seed.getBytes());
        byte[] result = encrypt(rawKey, cleartext.getBytes());
        return toHex(result);
    }

    /**
     * AES解密
     */
    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 ""; &

补充：综合编程 , 安全编程 ,