Cryptography has been used for thousands of years to help to provide confidential communications betw

Cryptography has been used for thousands of years to help to provide confidential communications between mutually trusted parties. In its most basic form, two people, offend noted as Alice and Bob, have agreed on a particular secret key. At some later time, Alice may wish to send a secret message to Bob (or Bob might want to send a message to Alice).The key is used to transform the original message (which is usually termed the plain text) into a scrambled form that sun intelligible to anyone who does not possess the key. This process is called encryption and the scrambled message is called the cipher text. When Bob receives the cipher text, he can use the key to transform the cipher text back into the original plain text; this is thedecryptionprocess.Acryptosystemconstitutesacompletespecificationofthe keys and how they are used to encrypt and decry pt information.

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