EncrypAES.java

/**
 * 长大长新-长江大学校园安卓应用
 *
 * Copyright (C) 2014-2016 Rex Lee <duguying2008@gmail.com>
 *
 * This program is free and opensource software; 
 * you can redistribute it and/or modify
 * it under the terms of the MIT License
 */
package com.rex.yangtzeu.utils;

import java.security.SecureRandom;

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

import com.rex.yangtzeu.config.Key;

public class EncrypAES {
	/**
	 * 加密
	 * 
	 * @param cleartext
	 *            待加密文本
	 * @return 加密后文本
	 * @throws Exception
	 */
	public static String encrypt(String content) {
		String text = "";
		try {
			text = EncrypAES.encrypt(Key.secret_key, content);
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return text;
	}
	
	/**
	 * 解密
	 * 
	 * @param encrypted
	 *            密文
	 * @return 返回明文
	 * @throws Exception
	 */
	public static String decrypt(String content) {
		String text = "";
		try {
			text = EncrypAES.decrypt(Key.secret_key, content);
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return text;
	}

	private static String encrypt(String seed, String cleartext)
			throws Exception {
		byte[] rawKey = getRawKey(seed.getBytes());
		byte[] result = encrypt(rawKey, cleartext.getBytes());
		return toHex(result);
	}

	private 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;
	}

	private 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;
	}

	private 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));
	}

}