5h没人做出来的脑洞大开折磨人CTF，思路原来是这样...

/**
  * Tea算法
  * 每次操作可以处理8个字节数据
  * KEY为16字节,应为包含4个int型数的int[]，一个int为4个字节
  * 加密解密轮数应为8的倍数，推荐加密轮数为64轮
  */
 class Tea {
     //加密
     byte[] encrypt(byte[] content, int offset, int[] key, int times) {//times为加密轮数
         int[] tempInt = byteToInt(content,  offset);
         int y = tempInt[0], z = tempInt[1], sum = 0, i;
         int delta = 0x9e3779b9; //这是算法标准给的值
         int a = key[0], b = key[1], c = key[2], d = key[3];
 
         for (i = 0; i < times; i++) {
 
             sum += delta;
             y += ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
             z += ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
         }
         tempInt[0] = y;
         tempInt[1] = z;
         return intToByte(tempInt, 0);
     }
 
     //解密
     byte[] decrypt(byte[] encryptContent, int offset, int[] key, int times) {
         int[] tempInt =  byteToInt(encryptContent, offset);
         int y = tempInt[0], z = tempInt[1], sum = 0, i;
         int delta = 0x9e3779b9; //这是算法标准给的值
         int a = key[0], b = key[1], c = key[2], d = key[3];
         if (times == 32)
             sum = 0xC6EF3720; /* delta << 5*/
         else if (times == 16)
             sum = 0xE3779B90; /* delta << 4*/
         else
             sum = delta * times;
 
         for (i = 0; i < times; i++) {
             z -= ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
             y -= ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
             sum -= delta;
         }
         tempInt[0] = y;
         tempInt[1] = z;
 
         return intToByte(tempInt, 0);
     }
 
     //byte[]型数据转成int[]型数据
     private int[] byteToInt(byte[] content, int offset) {
 
         int[] result = new int[content.length >> 2];//除以2的n次方 == 右移n位  即 content.length / 4 == content.length >> 2
         for (int i = 0, j = offset; j < content.length; i++, j += 4) {
             result[i] = transform(content[j  + 3]) | transform(content[j + 2]) << 8 |
                     transform(content[j  + 1]) << 16 | (int) content[j] << 24;
         }
         return result;
 
     }
 
     //int[]型数据转成byte[]型数据
     private byte[] intToByte(int[] content, int offset) {
         byte[] result = new byte[content.length << 2];//乘以2的n次方 == 左移n位  即 content.length * 4 == content.length << 2
         for (int i = 0, j = offset; j < result.length; i++, j += 4) {
             result[j + 3] = (byte) (content[i] & 0xff);
             result[j + 2] = (byte) ((content[i] >> 8) & 0xff);
             result[j + 1] = (byte) ((content[i] >> 16) & 0xff);
             result[j] = (byte) ((content[i] >> 24) & 0xff);
         }
         return result;
     }
 
      //若某字节为负数则需将其转成无符号正数
     private static int transform(byte temp) {
         int tempInt = (int) temp;
         if (tempInt < 0) {
             tempInt += 256;
         }
         return tempInt;
     }
 
 }

import java.io.*;
 import java.nio.ByteBuffer;
 import java.nio.channels.FileChannel;
 
 public class TeaMain {
     private Tea tea;
     private int[] KEY = new int[]{//加密解密所用的KEY
             0xdfabcbfa, 0xfdbaecba,
             0xedbafced, 0xbfaecfda
     };
 
     public TeaMain() {
         this.tea = new Tea();
     }
 
     //通过TEA算法加密信息
     public byte[] encryptByTea(byte[] temp) {
         int n = 8 - temp.length % 8;//若temp的位数不足8的倍数,需要填充的位数
         byte[] encryptStr = new byte[temp.length + n];
         encryptStr[0] = (byte) n;
         System.arraycopy(temp, 0, encryptStr, n, temp.length);
         byte[] result = new byte[encryptStr.length];
         for (int offset = 0; offset < result.length; offset += 8) {
             byte[] tempEncrpt = tea.encrypt(encryptStr, offset, KEY, 32);
             System.arraycopy(tempEncrpt,  0, result, offset, 8);
         }
         return result;
     }
 
     //通过TEA算法解密信息
     public byte[] decryptByTea(byte[] secretInfo) {
         byte[] decryptStr = null;
         byte[] tempDecrypt = new byte[secretInfo.length];
         for (int offset = 0; offset < secretInfo.length; offset += 8) {
             decryptStr = tea.decrypt(secretInfo, offset, KEY, 32);
             System.arraycopy(decryptStr,  0, tempDecrypt, offset, 8);
         }
 
         int n = tempDecrypt[0];
         byte[] result = new byte[decryptStr.length - n];
         System.arraycopy(tempDecrypt,  n, result, 0, decryptStr.length - n);
 //        return new String(tempDecrypt, n,  decryptStr.length - n);
         return result;
     }
 
     public byte[] readFile(String path) throws IOException {
         File file = new File(path);
         FileInputStream in = new FileInputStream(file);
         FileChannel channel =  in.getChannel();
         ByteBuffer byteBuffer =  ByteBuffer.allocate((int) channel.size());
         while ((channel.read(byteBuffer)) > 0) {
         }
         channel.close();
         in.close();
         return byteBuffer.array();
     }
 
     public void writeFile(String path, byte[] data) throws IOException {
         File file = new File(path);
         FileOutputStream out = new FileOutputStream(file);
         out.write(data);
         out.close();
     }
 
     public static void main(String[] args) throws IOException {
         System.out.println("Hello World!");
 
         TeaMain main = new TeaMain();
 
         byte[] encryptInfo = main.readFile("/Users/alset/Desktop/flag");
 
         byte[] decryptInfo =  main.decryptByTea(encryptInfo);
         System.out.print("解密后的数据：");
         System.out.println(decryptInfo);
         for (byte i : decryptInfo)
             System.out.print(i + " ");
         System.out.println();
         main.writeFile("/Users/a/Desktop/nothere", decryptInfo);
 
     }
 
 
 }