Cryptography is a very old science, whose goal is to secure communication, so that only its recipient could read it. There are a lot of methods to encrypt a message, from the simplest (like the 2000-year-old Cesar’s code) to the most complex (like the World War 2 Enigma code) ; they all need both encryption and decryption keys (sometimes identical). In some cases (such as the Hill cipher), the key is represented by a matrix.
Process :
- transcript the key into numbers using the ASCII table,
- convert the numbered key into a square matrix, the smallest possible size, and filling the lines first,
- transcript the clear message into numbers using the ASCII table,
- convert the numbered message into a matrix ; its number of columns should fit the key matrix size, and its number of lines should be as small as possible,
- multiply the 2 matrices, and write the answer linearly to get the encrypted message.