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History > History - Pg. 64

64 The Basics of Information Security The science of breaking through the encryption used to create the ciphertext is referred to as cryptanalysis and is practiced by cryptanalysts. The overarching field of study that covers cryptography and cryptanalysis is referred to as cryp- tology and is practiced by cryptologists. The specifics of the process used to encrypt the plaintext or decrypt the cypher- text is referred to as a cryptographic algorithm. Cryptographic algorithms gen- erally use a key, or multiple keys, in order to encrypt or decrypt the message, this being roughly analogous to a password. The range of all possible values for the key is referred to as the keyspace. We may also refer to the cryptosystem, a concept that covers a given algorithm and all possible keys, plaintexts, and ciphertexts. HISTORy History is rich with the use of cryptography, with some of the oldest examples being used by the ancient Greeks and Romans. Information was hidden by a wide variety of codes, by tattooing them on the shaved heads of messengers and then allowing the hair to grow, and by a multitude of other methods. Enough historical information exists to fill an entire volume, and indeed many