The Pigpen cipher is a simple substitution cipher which places letters on a geometric grid and exchanges the letters for symbols created.

This cipher is also known as the Masonic cipher, the Rosicrucian cipher, or the tic-tac-toe cipher. This cipher format is considered to be relatively ancient but rather worthless for security as it has become incredibly well known in modern times- even being regularly featured in children's books on ciphers and codes.