SCTF ANDROID CHAL SOL 1

SOLUTION.java

package com.x64mayhem;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.Array;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.Base64;

public class Main {
    public static void main(String[] args) throws IllegalAccessException, UnsupportedEncodingException {
        String KINDOFMAGIC[]={"UEBxWw==", "Sk5xVcOICw==", "bnRX", "S0BgWw==", "Nw==", "R0ZxRMOLElk=", "TkJhWw==", "dHZHdcOl", "eWRNYQ==", "bHRSeMOi", "R05tVw==", "d2hScA==", "T0xyVMOADQ==", "f2pQ", "Q0xsVw==", "Nw=="};
        String magic= "7E3Q5fm4lBSKXaHTnlCO52VL/iY6f+hQQ35oeFphtZIu3pf0QuOEpFB5nTeg8GTx";

        int length = Array.getLength(KINDOFMAGIC);
        Base64.Decoder decode=Base64.getDecoder();
        byte[] NEWBYTEARRAYKOM = new byte[length];
        for (int i = 0; i < length; i++) {
            Object obj = Array.get(KINDOFMAGIC,i);
            byte[] invoke3 = decode.decode(obj.toString());
            String hmm = d(new String(invoke3,"UTF-8"), i ^ 137);
            NEWBYTEARRAYKOM[i] = ((byte) hmm.charAt(0));
        }

        a.class.getDeclaredFields()[0].set(null, NEWBYTEARRAYKOM);
        Base64.Decoder decoder=Base64.getDecoder();
        byte[] bdecode=decoder.decode(magic);
        byte[] ANSWER =a.a(bdecode);
        //PRINT FLAG
        System.out.println(new String(ANSWER));
        
        // TOOL FOR DECODING INSTRUCTIONS
//        System.out.println(d(">JÂ0ûDwù¯0Õ´zhÝ!ë\u000ff", -989022505));
    
    }

    public static int INTGET=1;
    public static char a(char c, int i) {return (char) (c & ((1 << i) ^ 65535));}
    public static char b(char c, int i) { return (char) (c | (1 << i));}
    public static char c(char c, int i) {return (char) ((c & (1 << i)) >> i);}
    public static String d(CharSequence charSequence, int i) {
        StringBuilder sb = new StringBuilder();
        if (i == 0) {return sb.toString();}
        for (int i2 = 0; i2 < charSequence.length(); i2++) {
            char charAt = charSequence.charAt(i2);char c = (char) (i >> (i2 % 4));int i3 = i2 % 3;
            if (i3 == 0) {
                for (int i4 = 0; i4 < 8; i4 += 2) {char c2 = (char) (c(charAt, i4) ^ c(c, i4));
                    if (c2 == 0) {charAt = a(charAt, i4);} else if (c2 == 1) {charAt = b(charAt, i4);}}} else if (i3 == 1) {
                for (int i5 = 1; i5 < 8; i5 += 2) {
                    char c3 = (char) (c(charAt, i5) ^ c(c, i5));if (c3 == 0) {charAt = a(charAt, i5);
                    } else if (c3 == 1) {charAt = b(charAt, i5);}}} else if (i3 == 2) {
                for (int i6 = 0; i6 < 8; i6++) {char c4 = (char) (c(charAt, i6) ^ c(c, i6));if (c4 == 0) {charAt = a(charAt, i6);}else if (c4 == 1) {charAt = b(charAt, i6);}}}
                sb.append((char) (charAt ^ INTGET));
        }
        return sb.toString();
    }}