The Caesar cipher is one of the oldest forms of cryptography in recorded history, with instances stretching
back long before it was first named. Nonetheless, the cipher finds itself named for, and consistently
associated with, the famous Roman Emperor and General Julius Caesar. It was Caesar who reportedly used the
cipher with a shift of three to encode military messages to his commanders while on a campaign. After his
assassination, Caesar's nephew Augustus carried on his uncle’s usage of the cipher to protect his
correspondence but changed his messages encryption to a right shift of one. Despite the presence of more
complex codes, the cipher was likely favored by the emperors due to its simplicity. The cipher was likely
effective due to the illiteracy of many of those who would intercept them and a common misconception that
the messages were written in a mysterious foreign language. Enforcing this assumption of security is the
lack of evidence that any methods for solving substitution ciphers existed at the time, with the first
instances of frequency analysis appearing in the middle east centuries after Caesar's death.
Despite its growing ineffectiveness in the modern era, the cipher would nonetheless remain in use by various
groups for less vital communications such as by Jewish groups to encrypt the name of god on the mezuzah and
later by people wishing to exchange messages in plain view by posting encoded passages in newspapers.
Nevertheless, the last major use of the cipher for warfare was by imperial Russian forces in the first world
war due to the common soldiers struggling to understand more complex encryption methods. A choice that was
found to be a failure as contemporary German and Austrian code-breakers were easily able to decipher any
messages sent in the code.
Regardless of being phased out well over a century ago, the Caesar cipher has not fallen out of use
entirely. In 2006 a Sicilian mob boss named Bernardo Provenzano was captured by police due to his usage of
an altered version of the Caesar cipher where letters were replaced by numbers after their shift. Likewise
in 2011, a British counter-terrorist operation foiled a planned airline bombing due to the usage of an
easily breakable Caesar cipher by the perpetrators in their internet communications.