Ever since strategic planning required secrecy for the element of surprise, ciphers, crypotography (coming from the Greek for secret-writing) and cryptographic algorithms were developed. The complexity of ciphers marched hand in hand with advances in technology and mathematics. From the simplest shift and substitution ciphers, crackers now have to face the encryption and decryption of potentially quantum-entangled ciphers. If you are interested in finding out more, there is a good quick overview of encryption history, lists of ciphers as well as William Stalling’s interesting page on cryptography. I will upload my own lecture notes soon.
