Synchronous random number generators are an interesting topic. Multiple instances of a Java application can generate the same arrays of random numbers.

Such generators can use hardware elements (external digital noise streams), or they can only be software. Let's consider both of them and write Android Java applications

External digital streams can be used as a source for synchronous random number generators. The ideal option is a hardware generator with digital conversion. But for now, Android smartphones cannot yet receive information from satellites. Therefore, it is necessary to use Internet streams. But connections to a specialized server can be monitored and, at a minimum, distorted. Therefore, public Internet streams should be used. For example, Internet TV or Internet radio.

Internet radio channels include talk or news channels that are updated frequently. And use them as a digital stream. But this flow is not random. However, we can select numeric values that are far apart from each other from this stream. They are also not random. But the values of the selected numbers are independent of each other.
Such an array needs processing to increase entropy.
In a real application, the listing of which will be shown, the program listens to Internet radio and searches the stream for a given sequence of numbers (byte array). After this, a data buffer is written, from which “random” numbers are then selected, which are used by the XOR encryption.

On Github you can see a listing of a prototype application that receives an encryption key from an Internet radio stream, encrypts the text with the Vernam cipher, sends it via SMS to itself, receives the SMS, extracts the data and decodes it with the key. In a real application, it is necessary to add storage of dozens of encryption keys (cipherpad with pages), marking of the key used, checking the phone number of the SMS sender so as not to decode regular SMS.

A complete set of project files for an application that generates an array of random numbers based on an Internet radio stream, encrypts a given text with a Vernam cipher, sends SMS, receives SMS, extracts the encrypted text and decodes the original message. Markup file, manifest and Java listing.

https://github.com/vallshmeleff/speech2soundcryptokeysgen

I then modify the application project for sampling random numbers from an Internet radio digital stream to use it as a full-fledged extender of the original data and select pseudo-random numbers to be used as input for the next transformation (next level).
For now, let's consider another algorithm for generating pseudorandom numbers. Let me emphasize once again that all the random number “generators” being developed here are synchronous. Those. on two smartphones (for example, in London and in Prague), identical arrays of random numbers were generated for the same initial data. And at the same time, these smartphones do not exchange any data. Everything is hidden.
Application - Czech Entropy . The name doesn't mean anything. Maybe you even know that there is such an artistic object - a picture.

For synchronous independent random (pseudorandom) number generators, it is more difficult to achieve good entropy quality. But this topic is very interesting for programmers. I will finalize the application (the link to GitHub is published above) for a real working generator project (without the encryption function). This application will use numbers from the application as input Czech Entropy application

Applications Czech Flow and Czech Entropy are software random number generators. Applications use different algorithms. Czech Flow gets random numbers from Internet radio digital streams. These applications allow you to use received messages as input information. Those. create feedback, cross-data. You can use an application integrator and create generation systems with a large number of elements (see figure). Tens and hundreds of connections. In its original form - as in the kaotinka above

It is absolutely clear that Android, iOS or Windows are not suitable for serious cryptography. These operating systems have external management (or control). But Android is a convenient platform for creating and testing prototypes. And then transfer the solutions to your own Linux builds.

I’m currently preparing Source application codes for publication on GitHub

Synchronous random number generators PRNG
      Let's look at several ways to create software random number generators using external digital streams and without them. Let's write source code for Android Java - prototypes of applications showing the reality of using algorithms
      1. Generator of "random" numbers using expansion of source information, sampling and correction of source data.
      We will use TTS technology in this generator - converting the entered text into speech. This option is available in the Android operating system. TTS allows you to significantly increase the volume of data (30-100 thousand times), use different settings to obtain different digital results, ensure repeatability of the results (which makes it possible to build a PRNG), the transformation is “formulaless”. The disadvantages of the algorithm are obvious: the result is easily repeated (if you know the source text), large but not infinite expansion of the data, unstable level of entropy in the obtained data. Because the received data is a sound file, it may contain many repeating and dependent sequences of numbers.