6-6-2008 Network Security

Lecture on network secutiry and the theory of public key
(Chapter 3 of Textbook)

Secrect Key

*a key for encryption is also for decryption
*fast encryption and decryption
*problem with key distribution
*problem with keeping many keys

Public Key

*private key and public key
*public usually posted on an open directory
*private key must be kept in absolute private to oneself
*good for encryption and signature

Hash function
*fixed length of 128 or 256 bits
*fingerprint

do Lab Hash

Digital Signature
* privated key encrypted fingerprint of a plain text
*transmitted along with the plain text for verification

Man-in-the-middle attack

Digital Certificate
* Public Key signed with Certificate Authority

SSL (Secure Socket Layer)
* Using Digital Certificate, Digital Signature, Public Key Encryption, Hash (Message Digest)
* Instead of encrypting the sender's original text, only the session key generated by the sender is encrypted by the receiver's public key.
* The session key is valid throughout a session and not any longer.
* SSL is proposed by Netscape, Inc.
* https is actually http enhanced by SSL. https uses port 443 while http uses port 80.

範圍: 課本Chap. 3