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Suppose
that someone wants to send a message to a receiver, and wants to be
sure that no-one else can read the message. However, there is the
possibility that someone else opens the letter or hears the
electronic communication.
In cryptographic terminology, the
message is called plaintext or cleartext. Encoding the
contents of the message in such a way that hides its contents from
outsiders is called encryption. The encrypted message is
called the ciphertext. The process of retrieving the
plaintext from the ciphertext is called decryption.
Encryption and decryption usually make use of a key, and the
coding method is such that decryption can be performed only by
knowing the proper key.
Cryptography is the art or
science of keeping messages secret. Cryptanalysis is the art
of breaking ciphers, i.e. retrieving the plaintext without
knowing the proper key. People who do cryptography are
cryptographers, and practitioners of cryptanalysis are
cryptanalysts.
Cryptography deals with all aspects of
secure messaging, authentication, digital signatures, electronic
money, and other applications. Cryptology is the branch of
mathematics that studies the mathematical foundations of
cryptographic methods.
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