A Classical Cipher-Playfair Cipher and Its Improved Versions

In today's communications world, protecting data security cannot be ignored. Cryptography, which plays a pivotal role in information security, has become an indispensable and important part of information security. Cryptography is to study secret communication for adopting a kind of secret protection for the information to be transmitted. It is a technical science that studies the preparation and deciphering of codes. Classical encryption can be divided into two categories: transposition ciphers and substitution ciphers. This paper will mainly study a kind of substitution ciphers-Playfair cipher and review three improved versions of the 3D Playfair cipher. Then, a conclusion was drawn for these three improved versions of Playfair cipher. Finally looks forward to the future development of Playfair cipher and cryptography.