This is my solution to the Differential Cryptanalysis of the FEAL-4 algorithm [class takes in 2014]. This is a project from Dublin City University.

Download both *.java file:

• cryptaFEAL-4.java content the code for the Differential Cryptanalysis
• feal.java content the code from the course

Just launch the code and It should work. It takes around 1h30 to fully recover the key. I could have improved the computational cost of the algorithm. Don't hesitate to use another structure to improve the efficiency. If I remember correctly, at the end you should recover 4 different keys. All the keys are good yet the teacher wants you to give him only one key. Just give him all the correct keys and explain that all of them works just fine.

Note: You can find the real key by disassembling the java applet of the teacher. It will allow you to verify the correctness of your answer

I got 24/25