Computer and Network Security

1
Computer and Network Security

• SSL/TLS (Chapter 19)

2
SSL/TSL

• Assist E-commerce, banking, purchasing over the
  web
• Allow two parties to authenticate and establish
  a session key that is used to cryptographically
  protect the reminder of the session
• SSL (Secure Socket Layer) version 2 by Netscape
• SSL v3 by Netscape
• TLS (Transport Layer Security) by IETF

3
User Level Implementation

• SSL/TLS runs in a user-level process
• Runs on top of TCP
• Has its own units, called records, consisting of
  headers and payloads
• Four types of records user data, handshake
  messages, alerts, change cipher spec

4
Hand Shaking
5
Session Initiation
6
Session Resumption
7
Computing Keys

• Pre-master key S
• Master key K f ( S, RAlice, Rbob)
• Six session keys (for each direction, encryption
  key, integrity-protection key, IV), which are the
  hash results of K, RAlice, and Rbob.

8
Client Authentication

• Normally the clients send name/password to the
  server as application data
• The server has the option to send a certificate
  request in message 2 of the handshaking.

9
PKI

• The clients are pre-configured with a list of
  well-known trust anchors (CAs) when the software
  is shipped.
• The server either sends a certificate generated
  by one of those root CA, or sends a chain of
  certificates.