Public Key encryption procedure:
- the recipient's public key encrypts the message (the sender of the message do it and he cannot decrypt the encrypted message)
- the encrypted message is transmitted electronically to the receiver.
- the recipient's private key decrypts the message (the receiver do it. Only the person who holds the matching private key can read the message).
An analogy to public key encryption is that of a locked mail box..
- The public key is the mail slot. Anyone knowing the street address can go to the door and drop a written message.
- The private key is the key. Only the person who possesses the key can open the mailbox and read the message.
A keypair is often used to exchange an on-the-fly symmetric key, which will only be used for the current session.