Derandom

Predicts pseudo random numbers based on a sequence of observed numbers.

Usage

Enter a sequence of numbers that you obtained from a pseudo random number generator like, for instance, the Java standard pseudo random number generator or the Mersenne Twister MT19937. The app will then try to predict following numbers from the generator.

The app expects all numbers to be entered as integers or floating point numbers between zero and one. Currently, floating point numbers are supported for the Mersenne Twister only. Three input modes are supported:

1. Text field lets you enter the numbers directly on the device.
2. File lets you choose a file with newline separated number strings.
3. Socket opens a server socket on the device. You can then connect with a custom client by means of a client socket and send newline separated number strings to the server. After each number the server will send back the next newline separated predictions. Each block of predictions is separated by an additional newline.

To test the app, enter the following numbers in the Text field:

1412437139
1552322984
168467398
1111755060
-928874005

These numbers were sampled from the Java linear congruential generator Random.nextInt(). Thus, the app should detect LCG: Java after the third number input, and numbers in the prediction history should appear in green instead of red, indicating that those numbers were correctly predicted.

The following Python program can be used to test socket input. The program samples numbers from the standard Python pseudo random number generator and sends them to a network socket:

import random
import socket

HOST = "localhost"  # Host of Android device
PORT = 6869  # Default Derandom port
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.connect((HOST, PORT))
    buffer = s.makefile()  # Buffer for readline
    for _ in range(0, 700):
        # Sample bits from generator
        bits = random.getrandbits(32)
        # Send number string
        message = str(bits) + "\n"
        s.sendall(message.encode())
        # Read and print predictions
        for _ in range(0, 9):  # 8 predictions and newline
            line = buffer.readline()
            print(line, end="")

Start the app on the Android device and set the input spinner from Text field to Socket. Make sure that the device and the Derandom socket port (default 6869) are reachable in your network. Then set HOST in the Python program to the address of your Android device and run the program. For each number that is sent by the Python program, eight predictions are returned by Derandom and displayed by the Python program. After the app has received 624 numbers the Python Mersenne Twister should be detected and, in the app, numbers in the prediction history should appear in green instead of red. You can also replace random.getrandbits(32) with random.random() and send 1300 numbers instead of 700 numbers to account for unobserved bits.

Building from source

Define SDK location with sdk.dir in the local.properties file or with an ANDROID_HOME environment variable. Then type the following command to build in release mode:

./gradlew assembleRelease

License

Copyright (C) 2015-2024 Arno Onken

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.