# Cryptography: The Science of Encoding and Decoding Messages

Sending secret messages using codes has been a practice since the ancient time. In the Roman Empire, military officers would let messengers cut their hair, tattoo a secret message on their head, and send them to another place to relay the message once the hair had grown.

In Sparta, a device called  scytale consisting of a cylindrical tool with a strip of parchment was used to encode and decode messages.  Julius Caesar was known to perform letter substitutions to messages to make them unreadable. The method is now known as the Caesar cipher.

A scytale

Encoding and decoding messages became crucial during military campaigns.  It became popular particularly to mathematicians and even to popular persons. Even Edgar Allan Poe was known to be a great decoder during his time.

The practice of coding and decoding messages, now popularly known as encryption, has expanded and turned into one  major field called cryptography. Cryptography is a field that combines mathematics, computer science, and electrical engineering to develop the technology for secure communication. Several practical applications of modern cryptography are the use of passwords, ATMs, and electronic commerce.  Cryptography is one of the reasons why we can securely shop online, or why our email cannot be read by other people, or why we can send files from opposite sides of the world.

Cryptography at Its Finest (Humor)

With the use of computers, Caesar ciphers and other common encryption methods take only minutes to be decoded (or deciphered) nowadays. In effect, more complicated encoding schemes are done to disguise messages. One strategy is using  keywords, phrases, or even colors that have hidden meanings known only to both the sender and the receiver of the message. An example of such message is the son-father correspondence that follows.

***

\$chool i\$ really great. I am making lot\$ of friend\$ and \$tudying very hard. With all my \$tuff, I \$imply can’t think of anything I need, \$o if you would like, you can ju\$t \$end me a card, a\$ I would love to hear from you.

Love,

***
Dear Son,

I kNOw that astroNOmy, ecoNOmics, and oceaNOgraphy are eNOugh to keep even an hoNOr student busy. Do NOt forget that the pursuit of kNOwledge is a NOble task, and you can never study eNOugh.

Love,