"Cryptology" is the science of secret communications. The two branches or major subdivisions of cryptology are "cryptography" or the science of making and keeping communications secret and "cryptanalysis" or the science of discovering or breaking secret communications.

"Encryption" refers to the process of converting communications from human readable to some type of nonhuman readable form. "Decryption" refers to the process of converting communications from nonhuman readable form back to human readable form. Human readable communications or data is usually referred to as "plaintext" and nonhuman readable communications or data is usually referred to as "ciphertext."

Encryption and decryption processes and algorithms can be used to create digital signatures that uniquely identify the authorship of a message. An encrypted message itself plus a key provided by the author or a trusted third party can be used to decrypt the message and thereby prove both that the message was not altered and was encrypted by the author. If this were not so, the receiver would not be able to decrypt the message with the author's key.

A "key" is a word, value, or whatever that must be input along with the secret message into the decryption process in order to decrypt the ciphertext. It turns out that the length of the key or the size of the key space from which the key was selected has a critical impact on the strength of the protection provided by the encryption process. This is because in general...