In 1854, Sir Charles Wheatstone invented the cipher known as "Playfair," named for his friend Lyon Playfair, first Baron Playfair of St. Andrews, who popularized and promoted the cipher. Its ...

The goal of AES was not only to select a new cipher algorithm but also to dramatically increase both the block and key size compared with DES. Where DES used 64-bit blocks, AES uses 128-bit blocks.

Like the Playfair, the Double Playfair cipher uses 5x5 squares. In this case two keywords are chosen, and each square is filled in the same way as the Playfair.