安卓加密

用JEB反编译出来找到关键函数check2

public void check2(String arg15) {
        String v5;
        int v4 = 0;
        int[] v7 = new int[16];
        int v3 = 16;
        int v1 = 5;
        v7[2] = 3;
        v7[7] = 4;
        v7[3] = 8;
        v7[1] = 10;
        v7[10] = 11;
        v7[0] = 15;
        v7[11] = 20;
        v7[6] = 20;
        v7[8] = 21;
        v7[15] = 24;
        v7[12] = 30;
        v7[13] = v3;
        v7[4] = 3;
        v7[14] = v3;
        v7[9] = 3;
        v7[5] = 89;
        if(arg15.length() != 16) {
            throw new RuntimeException();
        }

        try {
            v5 = this.getKey();
        }
        catch(Exception v0) {
            v5 = this.getKey();
            System.arraycopy(v5, 0, arg15, v1, v1);
        }

        while(v4 < arg15.length()) {
            if((v7[v4] & 255) != ((arg15.charAt(v4) ^ v5.charAt(v4 % v5.length())) & 255)) {
                throw new RuntimeException();
            }

            ++v4;
        }
    }
public String getKey() {
        return "goodluck";
    }

其实就只有一个异或操作，直接写脚本

#include <iostream>
using namespace std;
int main()
{
    int v4 = 0;
    int v3 = 16;
    int v1 = 5;
    int v7[16];
    v7[2] = 3;
    v7[7] = 4;
    v7[3] = 8;
    v7[1] = 10;
    v7[10] = 11;
    v7[0] = 15;
    v7[11] = 20;
    v7[6] = 20;
    v7[8] = 21;
    v7[15] = 24;
    v7[12] = 30;
    v7[13] = 16;
    v7[4] = 3;
    v7[14] = 16;
    v7[9] = 3;
    v7[5] = 89; 
    string v5 = "goodluck";
    string flag="";
    while(v4<16){
        flag+=(char)(v7[v4]^((int)v5[v4%v5.length()]));
        v4++;
    }
    cout<<flag<<endl;
    return 0;
}