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Public Key Infrastructure/Technology is a
Cryptographic system that uses two keys - a Public Key, known
to everyone and a Private or Secret Key, known only to the
recipient of the message.
When John wants to send a secure message to
Jane, he uses Jane's Public Key to encrypt the message. Jane
then uses her Private Key to decrypt it.
An important element to the Public Key system
is that the Public and Private Keys are related in such a
way that only the Public Key can be used to encrypt messages
and only the corresponding Private Key can be used to decrypt
them. Moreover, it is virtually impossible to deduce the Private
Key if you know the Public Key.
Public Key systems, such as Pretty Good Privacy
(PGP), are becoming popular for transmitting information
securely via the Internet. They are extremely secure
and relatively simple to use. The only requirement with
Public Key systems is that you need to know the recipient's
Public Key to encrypt a message for him or her.
Public Key cryptography was invented in 1976
by Whitfield Diffie and Martin Hellman. For this reason,
it is sometime called Diffie-Hellman encryption. It
is also called asymmetric encryption because it uses
two keys instead of one key (symmetric encryption).
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