简单字符串加密工具

在网上找了一个简单的字符串DES加密解密工具:DesUtil

package com.ftk.eloan.framework.utils;

import java.security.Key;
import java.security.Security;

import javax.crypto.Cipher;

/**
 * DES加密 解密算法
 * 
 * @author lifq
 * @date 2015-3-17 上午10:12:11
 */
public class DesUtil {
	private static String strDefaultKey = "tourhb";

	private Cipher encryptCipher = null;

	private Cipher decryptCipher = null;
	
	private static DesUtil desUtil;

	public static void main(String[] args) {
		try {
			String test = "43020719800203401X_20170802";
			DesUtil des = DesUtil.getInstance(null);// 自定义密钥
			System.out.println("加密前的字符：" + test);
			System.out.println("加密后的字符：" + des.encrypt(test));
			System.out.println("解密后的字符：" + des.decrypt(des.encrypt(test)));

			System.out.println("解密后的字符：" + des.decrypt("fe14c7c41f7d2a94b07d7928b21346e7"));

		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public static DesUtil getInstance(String key){
		if(desUtil == null) {
			try {
				if(key == null||key.trim().length()<=0){
					desUtil = new DesUtil();
				}else{
					desUtil = new DesUtil(key);
				}
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		return desUtil;
	}
	
	public static String byteArr2HexStr(byte[] arrB) throws Exception {
		int iLen = arrB.length;
		// 每个byte用两个字符才能表示，所以字符串的长度是数组长度的两倍
		StringBuffer sb = new StringBuffer(iLen * 2);
		for (int i = 0; i < iLen; i++) {
			int intTmp = arrB[i];
			// 把负数转换为正数
			while (intTmp < 0) {
				intTmp = intTmp + 256;
			}
			// 小于0F的数需要在前面补0
			if (intTmp < 16) {
				sb.append("0");
			}
			sb.append(Integer.toString(intTmp, 16));
		}
		return sb.toString();
	}

	public static byte[] hexStr2ByteArr(String strIn) throws Exception {
		byte[] arrB = strIn.getBytes();
		int iLen = arrB.length;

		// 两个字符表示一个字节，所以字节数组长度是字符串长度除以2
		byte[] arrOut = new byte[iLen / 2];
		for (int i = 0; i < iLen; i = i + 2) {
			String strTmp = new String(arrB, i, 2);
			arrOut[i / 2] = (byte) Integer.parseInt(strTmp, 16);
		}
		return arrOut;
	}

	private DesUtil() throws Exception{
		
			this(strDefaultKey);
	}

	private DesUtil(String strKey) throws Exception {
		Security.addProvider(new com.sun.crypto.provider.SunJCE());
		Key key = getKey(strKey.getBytes());

		encryptCipher = Cipher.getInstance("DES");
		encryptCipher.init(Cipher.ENCRYPT_MODE, key);

		decryptCipher = Cipher.getInstance("DES");
		decryptCipher.init(Cipher.DECRYPT_MODE, key);
	}

	public byte[] encrypt(byte[] arrB) throws Exception {
		return encryptCipher.doFinal(arrB);
	}

	public String encrypt(String strIn) throws Exception {
		return byteArr2HexStr(encrypt(strIn.getBytes()));
	}

	public byte[] decrypt(byte[] arrB) throws Exception {
		return decryptCipher.doFinal(arrB);
	}

	public String decrypt(String strIn) throws Exception {
		try {
			return new String(decrypt(hexStr2ByteArr(strIn)));
		} catch (Exception e) {
			return "";
		}
	}

	private Key getKey(byte[] arrBTmp) throws Exception {
		// 创建一个空的8位字节数组（默认值为0）
		byte[] arrB = new byte[8];
		// 将原始字节数组转换为8位
		for (int i = 0; i < arrBTmp.length && i < arrB.length; i++) {
			arrB[i] = arrBTmp[i];
		}
		// 生成密钥
		Key key = new javax.crypto.spec.SecretKeySpec(arrB, "DES");
		return key;
	}
}