Connect Four in C

And here we are again!

After all these cryptographic methods I was thinking: maybe this blog is becoming too much serious. I need to give a little of fun to my poor readers.

For this reason I recover from the grave an old program in C that I created in my Bachelor. It was in Italian language, but… Come on! You don’t have to worry! I translate this game in English and I correct some small bugs. So! Have fun!

Eh?!? I didn’t say what about is this program? Really? Oh…

As you can read from the title is “Connect four” on terminal. A simple picture so you can understand better what I am talking.

This is connect four

It is a turn game 1 against 1 where you need to be the first to insert four coins in line horizontally, vertically or diagonally.

In my version you can play against a friend or, if you are alone, against a little smart pc. It is not a very high AI, but it can provide a small challenge.

At the end of every match, a score and the time used will be saved on your pc. In this way you will be able to recover easily the chronology of your matches!

Full of smiles! ūüėÄ

Instructions and rules are also provided inside of the game. You can download it by here.

Connect Four in C

Give a try and let me know what you think!

Your sincerely,
Stefano Martin

AES with C

Welcome everybody again!

This week is a cryptographic period and I want to present again AES.

AGAIN?!? Ok… I can understand your concern. Already in the last week I gave you a very similar program in Java. But there was something that bothers me.

When I want to protect something, I want to be able to protect everything. With Java I¬†was quite happy to be able to encrypt any type of language (Chinese, Russian, Italian, Arabic, and so on). But it was not enough for me. I didn’t want¬†only to encrypt simple text files, but even pictures, video or more complicate files.

A simple example of how to use this new program

For this reason I recover an old friend called C and I went brutally on the basis of the file code. To overcome¬†the simple letter structure as¬†‘A’, ‘b’ or ‘ŤÉ°’ and transcend in the fantastic world made of zeros and one, i.e. something like this 10101010101.

I am happy thus to make you available a new program in C, downloadable without any problem by here.

AES-128, AES-192 and AES 256, this time in C

Which are the advantages of this version?
+  You can encrypt (and decrypt) any files.
+  It it faster than Java
+  It works fine in Linux too (here the download for Linux version)

Which are the disadvantages?
Р The application is not user friendly (you need to use the terminal)
Р It is a little harder to select the file that you want to encrypt (or decrypt)

Give a try! But be careful! I will give you the same alert of the last time. If you encrypt a file and you delete the original one (DON’T DO IT), then you can recover your original document only if you own the password. I can’t accept any responsibility or liability for damages arising from the misuse of this program.

Your sincerely,
Stefano Martin

AES with Java

Welcome everybody!

Today I want to show a new Java created by myself. It is useful in the case that you want to protect your messages from possible eavesdropper. If you like stories of espionage, the names of Snowden and Wikileaks will not sound new to you. In both the cases the protection or discovery of a secret were the main point of the debate.

When we want to protect our message we are doing “cryptography”.

In general, when we want to protect our message we are doing “cryptography”. At the contrary, if¬†we want to discovery a message (without a password) we are doing “cryptanalysis”. With the java program that you can download from the next link, we are doing “cryptography”.

AES-128, AES-192, and AES-256 in one program

With this program you will be able to encrypt and decrypt text files (not photos, programs or videos) with one of the most secure method of encryption: AES-256 (or alternatively AES-128 or AES-192).


To create this Java program I used the original paper that the authors, Joan Daemen and Vincent Rijmen, used to propose Rijndael, better known as AES. At this link you can find the original pdf.

For¬†the creation of this program¬†I found two interesting problems: the first one was¬†of mathematical nature. To work¬†with a field with 256 elements, called GF(256), is not simple and required some notion of not trivial algebra. Especially if you don’t understand that¬†he chosen “x” in GF(256) is not a primitive element, but “x+1” it is. Luckily my PhD came¬†to help me, and the creation of a the encryption systems was not really hard for myself.¬†The use of Sage (Python with mathematical steroids) was fundamental to create efficiently this mathematics part.¬†¬†If you don’t understand the problem, don’t worry! And be happy!

This is a good friend for a programmer that wants to use mathematics.

The second problem was with the implementation of AES. By having a Chinese wife and being myself Italian, I should use symbols as “śąĎ” or “√©”. For this reason I¬†should say goodbye to my old friend UTF-8 and say welcome to UTF-16 and its UNICODE world. It was not really challenging, but still interesting.

Give a try! But be careful! If you encrypt a file and you delete the original one (DON’T DO IT), then you can recover your¬†original document¬†only if you own the password. I¬†can’t accept¬†any responsibility or liability for damages arising from the misuse of this program.

Your sincerely,
Stefano Martin


Project Euler

One famous website to test your own ability to code is Project This website offers over 500 different challenges that can be solved only by the use of some programming language.

The programming language of my choice is Java. Thus with courage and ambition I started quickly to write and compile lines and lines of codes.

Since I just began, the quantity of my solved exercises (25) is not actually exciting. But it permits me to obtain the first level of Euler that equivals to be in the 14.75% of people that was able to solve at least 25 problems.

I want to add one thing: the exercise usually are very specific, by requiring an exact value. For example problem¬†7 asks: “What is the 10001st prime number?”
My program solves instead: “What is the n-th prime number?” where n is a positive integer. I like to have more general answers.

If you are curious you can find my Bitbucket repository here: click me!

Oh! About the repositories! At the bottom of my webpage you can find now a small bucket. That one will permit you to find my repositories on Bitbucket.

Stefano Martin