Oranchak explained that the note was a transposition cipher, which rearrange messages in a variety of ways, such as rearranging columns of a message. The man and his colleagues then developed an app ...

Image by Wolfman12405, licensed under CC BY-SA 4.0, via Wikimedia Commons.

A toy implementation of a Feistel Network. Supports 256 bit keys with 16 rounds over a XOR cipher. Built primarily for education.