Cryptography, a Method of Hidi

By: Harem Hushiar Abdulfattah, MA, 2005

Cryptography is a method of protecting information and communications through the use of codes so that only those for whom the information is intended can read and process it. The word "cryptography" is derived from the Greek Krypto’s , meaning hidden. The prefix "crypt-" means "hidden", and the suffix "-graphy" stands for "writing." The origin of cryptography is usually dated from about 2000 B.C. with the Egyptian practice of hieroglyphics. The first known use of a modern cypher was by Julius Caesar (100

B.C. to 44 B.C.), who did not trust his messengers when communicating with his governor sand officers.

In simple words Cryptography is the science of information security or the art and science of secret writing. And individuals who practice this field are known as cryptographers. In the basic communication scenario, we assume that it is a game between three parties:

• a sender (e.g., an embassy).

• a receiver (e.g., the government office).

• an opponent (or a hacker, e.g., a spy).

A good way to understand the specifics of what we're talking about is to look at one of the earliest

known forms of cryptography. The diameter of the Scytale can be regarded as one of the oldest classic cypher's keys. In which Ancient Greece's messenger belt was composed of a leather stretch with characters written on the backside. It seemed like a meaningless sequence of characters, but an encoded message can be read when the stretch of leather is winded around a piece of wood with the correct diameter as shown in the above pictures. Those were the days when cryptography had almost entirely military applications. The idea here is that, while keeping your cryptographic system a secret would be nice, your opponent will almost certainly eventually figure it out, that is why there is need for updating the methods continuously. Recently, cryptography has become a battleground for some of the world's best mathematicians and computer scientists. Because it is no longer a physical instrument, it is now using computer applications for it. For example, the ability to securely store and transfer sensitive information

has proved a critical factor in success in war and business. In computer science, cryptography refers to secure information and communication techniques derived from mathematical concepts and a set of rule-based calculations called algorithms to transform messages in ways that are hard to decipher. These deterministic algorithms are used for cryptographic key generation, digital signing, and verification to protect data privacy, internet browsing, and confidential communications such as credit card transactions and emails. Cryptography is closely related to the disciplines of cryptology and cryptanalysis. It includes techniques such as microdots, merging words with images and other ways to hide information in storage or transit. However, in today's computer centric world, cryptography is most often associated with scrambling plaintext (ordinary text, sometimes referred to as clear text ) into ciphertext which is the disguised message (a process called encryption), then back again into normal text (known as

decryption).