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Encryption is the process of converting a plaintext message
into an alternate ciphertext message. The ciphertext message contains all the
information of the plaintext message, but is not in a format readable by a human or computer without the proper mechanism to
decrypt it.
The inverse process, of extracting the original information, is called decryption and can only be accomplished using auxiliary information, called a key.
Most encryption methods can be divided into symmetric
key algorithms and asymmetric key algorithms.
In a symmetric key algorithm (e.g., DES and AES), the sender and receiver must have a shared key set up in advance and kept secret from
all other parties; the sender uses this key for encryption, and the receiver uses the same key for decryption. In an asymmetric key algorithm (e.g., RSA, and the most common use of PGP), there are two separate keys: a public
key is published and enables any sender to perform encryption, while a private key is kept secret by the receiver
and enables him to perform decryption.
See also
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