create attack.py file

[thomaspeyrin]

We need to create a attack.py file, so we can define there the various attack scenario and generate the models accordingly. For example one attack can be:

def differential_path_search(primitive, number of rounds, model_type):

• generate the model of the primitive (with some models version chosen by default)
• generate the extra constraints for the attack (for example set input different to 0)
• define optimization target
• let the use add/modify himself the modeling (for example, he wants a certain diff version modelling for some Sboxes)

[ChunningZhou]

I have created the attack.py file, which includes functionality for searching single-key differential trails using MILP and SAT methods. The functions within it will be further developed and completed later.