package com.example.qurenwu.qurenwu_2.util;

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");

        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG","Crypto");

        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;

    }

    /**

     * 加密

     * @param raw

     * @param clear

     * @return

     * @throws Exception

     */

    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;

    }

    /**

     * 解密

     * @param raw

     * @param encrypted

     * @return

     * @throws Exception

     */

    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));

    }

}

password = AESEncryptor.decrypt(AES_SEED, password);  // AES_SEED是种子码，我也不清楚具体什么作用，反正可以随自己定义