|Subject||Computer and Network Security|
|NU Year||Set: 1.(b) Marks: 2+3 Year: 2014|
Encryption is performed to ensure the safety and privacy of information sent from one party to another. “Keys” are used to lock (encrypt) and unlock (decrypt) the data that’s transmitted, and if a single key is used for this purpose then symmetric encryption is said to have occurred. This method only works when the key that’s used is kept absolutely secure, and as a secret between the two communicating parties.
But for most practical applications, several parties or communication transactions may be involved, and it becomes necessary for encryption keys to be transmitted over networks whose security may be in doubt. That’s where asymmetric encryption comes into the picture.
Here, a pair of keys is used to encrypt or decrypt communications. There’s a private key, held separately by its owner, and a public key which can be visible to everyone, and distributed to intended recipients. Messages are encrypted with the public key, then decrypted by the holder’s unique private key – which may also be used in creating digital signatures.
Public Key Infrastructure (PKI) uses a combination of asymmetric and symmetric processes. An initial “handshake” between communicating parties uses asymmetric encryption to protect the secret key which is exchanged to enable symmetric encryption. Asymmetric encryption is used for the rest of the communication, once the secret key has been exchanged.