BUUCTF--Java逆向解密

测试文件：https://www.lanzous.com/iandl8f

 

代码分析

使用jd-gui打开文件（点击下载）

import java.util.ArrayList;
import java.util.Scanner;

public class Reverse {
  public static void main(String[] args) {
    Scanner s = new Scanner(System.in);
    System.out.println("Please input the flag );
    String str = s.next();
    System.out.println("Your input is );
    System.out.println(str);
    char[] stringArr = str.toCharArray();
    Encrypt(stringArr);
  }
  
  public static void Encrypt(char[] arr) {
    ArrayList<Integer> Resultlist = new ArrayList<>();
    for (int i = 0; i < arr.length; i++) {
      int result = arr[i] + 64 ^ 0x20;
      Resultlist.add(Integer.valueOf(result));
    } 
    int[] KEY = { 
        180, 136, 137, 147, 191, 137, 147, 191, 148, 136, 
        133, 191, 134, 140, 129, 135, 191, 65 };
    ArrayList<Integer> KEYList = new ArrayList<>();
    for (int j = 0; j < KEY.length; j++)
      KEYList.add(Integer.valueOf(KEY[j])); 
    System.out.println("Result:");
    if (Resultlist.equals(KEYList)) {
      System.out.println("Congratulations);
    } else {
      System.err.println("Error);
    } 
  }
}

很简单的一个列表运算。

 

脚本

# -*- coding:utf-8 -*-

KEY = [180, 136, 137, 147, 191, 137, 147, 191, 148, 136,
    133, 191, 134, 140, 129, 135, 191, 65]

flag = ''
for i in KEY:
    flag += chr((i^0x20)-64)
print ('flag{'+flag+'}')

 

get flag！

flag{This_is_the_flag_!}