-Cryptography is the area of knowledge that studies the theory and methods that are used for protecting information so that non-authorized persons cannot understand it. A *cryptographic system* is a system that transforms a *clear text message* (a message that is understandable to humans) to a *cyphered* text (text that is unintelligible to unauthorized persons). Authorized persons can *decypher* the *cyphered* text to obtain the original cleartext.
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