Cryptography is the ancient science of writing in code. The first documented use occurred in Egypt around 1900 B.C. when a scribe used nonstandard hieroglyphs to create an inscription. Later, around 1500 B.C. in Mesopotamia, Cuneiform signs were used in the least common syllabic values, in an attempt to hide the formula of a special pottery glaze used on the tablet on which it was written.
The ATBASH cipher, a reverse alphabet, simple substitution cipher, was used between 500 and 600 B.C. by the Hebrews while writing the book of Jeremiah. This was followed in 486 B.C. by the Ancient Greek invention of the Skytale: a stick wrapped with narrow strips of papyrus, leather or parchment. After a message was written on the covering, the strip was removed and passed on to the intended recipient. The recipient had to have the same size stick to be able to read the message properly after wrapping the strip around it. Even Julius Caesar had a simple substitution cipher that he used to protect military messages.
Cryptography continued to evolve and develop through the centuries with military and business applications. As technology advanced, more and more complex ciphers were developed. By 1971, the first civilian block ciphers were being created by Horst Fesitel of IBM. The name of the project was Lucifer.
The computer era had begun, and with it came the need for security in mainframes and networks. In 1976, Whittfield Diffie and Martin Diffie published the first Public Key Cryptography, which was called the Diffie-Hellman key exchange. It established a secret key through unprotected communications channels without having a prior shared secret.
Public key cryptosystems utilize the concept of one-way functions that are more appropriate for non-military applications such as business transactions and data privacy when performing operations such as sending a confidential message, authenticating a message, ensuring user privacy when accessing an electronic cash machine, and verifying the correct tally and confidentiality of votes submitted through an electronic voting machine, to name a few. Public key cryptosystems are still in use today.
Along with Public key cryptography there are two other basic algorithms that are used to provide security. Secret Key cryptography uses a single key for encryption and decryption, while Hash Functions uses a mathematical transformation to encrypt information in an irreversible process.
Random number generators are also used in cryptology to generate keys. This makes the key harder to guess by frequency analysis and other methods. Just as there are different types of randomness, so are there different types of random number generators.
Additional resources and information on cryptology are available in the form of books such as Applied Cryptography, by Bruce Schneier, which is an introduction to cryptology, and Cryptography: Theory and Practice, Third Edition, by Douglas R. Stinson, which includes comprehensive updates in the field of cryptography.
Journals are another source of information. The Journal of Cryptology is the official journal of the International Association for Cryptologic Research.
Forbes recently published an article on the founding of Cryptography Research, a San Francisco-based firm that solves complex data security problems. This supports the evidence that there is a growing demand for cryptography experts.
Conferences relating to Cryptography and security are also popular. A comprehensive Conference list is available online. If attending a conference is out of the question, a database of Conference papers presented at Crypography conferences is also online.