彥霖 實驗筆記

原文章：http://jian-zhoung.blogspot.tw/2013/12/java-des.html

原文寫得比較好，我這裡只是做紀錄 : D

輸出結果：

加密前的字符：這是測試資料
加密後的字符：6dc2c6cd7666d848eab7e08e0df223d7da55ce1144d711b8
解密後的字符：這是測試資料

程式碼：


public class Test {

    public static void main(String[] args) throws Exception {

        String test = "這是測試資料";
        DES des = new DES("蘿莉之門");//自定義密鑰
        System.out.println("加密前的字符：" + test);
        System.out.println("加密後的字符：" + des.encrypt(test));
        System.out.println("解密後的字符：" + des.decrypt(des.encrypt(test)));

    }

}

import javax.crypto.Cipher;

/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
/**
*
* @author Loli
*/
public class DES {

private static String strDefaultKey = "Loli"; //預設的金鑰
private StringBuffer objSb = null;
private Cipher objCipher = null;
private java.security.Key objKey = null;
private int intStringLength = 0;
private int intTemp = 0;

//預設建構子
public DES() throws Exception {
this(strDefaultKey);
}

//自訂密鑰
public DES(String arg_strKey) throws Exception {
setKey(arg_strKey.getBytes());
objCipher = Cipher.getInstance("DES");
}

//從指定的字串製成密鑰，密鑰所需的字元陣列長度為8位，不足及超過都要處理
private void setKey(byte[] arg_strPrivateKey) throws Exception {
byte[] arrTempByteArray = new byte[8];
// 將原始字元陣列轉換為8位
for (int i = 0; i < arg_strPrivateKey.length && i < arrTempByteArray.length; i++) {
arrTempByteArray[i] = arg_strPrivateKey[i];
}
// 設定密鑰
objKey = new javax.crypto.spec.SecretKeySpec(arrTempByteArray, "DES");
}

//將byte陣列轉換16進制值的字串，如：byte[]{1,18}轉換為：0112
public String byte2Hex(byte[] arg_bteArray) throws Exception {
intStringLength = arg_bteArray.length;
objSb = new StringBuffer(intStringLength * 2);
for (int i = 0; i < intStringLength; i++) {
intTemp = (int) arg_bteArray[i];
//負數需要轉成正數
if (intTemp < 0) {
intTemp = intTemp + 256;
}
// 小於0F需要補0
if (intTemp < 16) {
objSb.append("0");
}
objSb.append(Integer.toString(intTemp, 16));
}
return objSb.toString();
}

//將16進制值的字串轉成byte陣列
public byte[] hex2Byte(String arg_strHexString) throws Exception {
byte[] arrByteDAta = arg_strHexString.getBytes();
intStringLength = arrByteDAta.length;
byte[] aryRetuenData = new byte[intStringLength / 2];
for (int i = 0; i < intStringLength; i = i + 2) {
aryRetuenData[i / 2] = (byte) Integer.parseInt(new String(arrByteDAta, i, 2), 16);
}
return aryRetuenData;
}

//加密字串
public byte[] doEncrypt(byte[] arg_bteArray) throws Exception {
objCipher.init(Cipher.ENCRYPT_MODE, objKey);
return objCipher.doFinal(arg_bteArray);
}

public String encrypt(String arg_strToEncriptString) throws Exception {
return byte2Hex(doEncrypt(arg_strToEncriptString.getBytes()));
}

public byte[] doDecrypt(byte[] arg_bteArray) throws Exception {
objCipher.init(Cipher.DECRYPT_MODE, objKey);
return objCipher.doFinal(arg_bteArray);
}

//解密字串

public String decrypt(String arg_strToDecriptString) throws Exception {
return new String(doDecrypt(hex2Byte(arg_strToDecriptString)));
}
}