Understanding Network Security Fundamentals

1. COEN 350 Network Security Introduction

2. Computer Networks • OSI Reference Model • Application Layer • Presentation Layer • Session Layer • Transport Layer • Network Layer • Data Link Layer • Physical Layer

3. OSI Reference Model • Useful to establish terminology • Not implemented • Upper layer implemented in terms of lower layer.

4. OSI Reference Model • Application Layer • Locus of applications that use networking • P2P • HTTP • ftp • Presentation Layer • Encodes application data into a canonical form • Decodes it into system-dependent format at the receiving end.

5. OSI Reference Model • Session Layer • Extra functions over reliable one-to-one connection • RPC • Transport Layer • Reliable communication stream between a pair of systems. • IP, UDP, TCP, ICMP

6. OSI Reference Model • Network Layer • Computes paths across an interconnected mesh of links and packet switches • Forwards packets over multiple links from source to destination

7. OSI Reference Model • Data Link Layer • Organizes physical layer’s bits into packets and controls who on a shared link gets each packet. • Physical Layer • Delivers an unstructured stream of bits across a single link of some sort.

8. TCP/IP Suite

9. Protocol Layers and Security • Security measures often layer network protocols. • Protect contents of packages is protection at layer 2. • Still allows traffic analysis. • IPSec protects (encrypts) packages at layer 4 • Does not work with NAT.

10. Goals • Authentication • Who are you? • Authorization • Are you allowed to do that? • Integrity • Is this the real message? • Privacy • Does anyone else know about it?

11. Zone of Control • The zone that needs to be secured in order to prevent eavesdropping. • Physical access needs to be prevented. • Tempest program (US military) • All computer systems radiate information. • Possible to reconstruct image on a monitor from 20 ft. • Wireless access point rated for e.g. 50 ft radius for receiving data. • Special antenna (built from a Pringles box, etc.) can read traffic from a mile away. • Define a perimeter of a commercial wired network: • Need to include backdoor channels like modems, etc. • Tempest: Set of standards for limiting electric or electromagnetic radiation emanations from electronic equipment. • Shortcut for filed of compromising emanations / Emissions Security

12. Legal Issues • Patent Law • First inventor has the right to invention. • In other countries: First one to file. • Patents issued based on what inventors present regarding • Novelty (  Prior Art) • Importance (“Aha” effect) • Patent process flawed since Reagan under-funding, but slowly getting better • Patent decision needs to be made within a day. • Many cryptography algorithms are / were patented. • Are now moving into the public domain. • Still, many standards are built around patented methods. • Kerberos uses secret key encryption instead of public key encryption.

13. Legal Issues • Export Control • Cryptographic algorithms and tools were considered to be restricted technology. • Treated like ammunition. • Taking a laptop to Mexico for a week-end could be a violation of export control. • Government gave up after PGP fiasco • Zimmermann invented PGP 1.0 in 1991. • PGP fell under the ammunition clause. • Zimmermann circumvented export restriction by publishing code in book form (under first amendment protection) • Book was intended to be bought by exactly one person in Norway to scan in code and publish PGP outside of US (for free downloads).

14. Legal Issues • Key Escrow • Cryptography algorithms became unbreakable in the nineties. • Prevent wiretaps, computer forensics, etc. • National security efforts sponsored Clipper: • 1993 • Encryption chip with secret key. • User gets chip, secret key is broken up and stored at two different agencies. • Two different agencies needed to cooperate to recover secret key. • Considered to be almost impossible if cooperation were legal and impossible if cooperation were illegal. • Government gave up.