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 “我” or “é”. 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


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