An encrypted App? Interesting...

Give it to the French Military Secret Service or have them give you the software that decrypted Encrochat an encrypted and hidden messaging app used by European organised crime syndicates.

Basically all encryption works the same way by exchanging the letters with different symbols or numbers. 

That is done most of the times quite simple and there are letters more often used than others

Count the e in this text and the z.

Now you need a software that takes the raw file in binary code and looks for the most often binary string like eg 

10010100111100011

That would be an e most likely. 

Enjoy 

#gfyNSA you could have known that.