CISC 210 - Class Today

CISC 210 - Class Today • Project Schedule • Upcoming Lab • Recap • Protocols and Layering • Network Encryption • Link vs Network vs Application R. Smith - University of St Thomas - Minnesota

Project Schedule • April 22: 1 week after Easter • Project Proposal DUE • You want to start working on the project NOW • You want to have your team in place ASAP • April 27: 1 week later • Project OUTLINE Due • The outline is a bit of work • It counts for a chunk of the assignment (20% or so) • DON’T MESS IT UP R. Smith - University of St Thomas - Minnesota

The Lab • Lab Objective: map the lab machines • Lab Groups • I’ve assigned groups via e-mail – I’ll also post groups • Do the labs as a group (this one and future ones) • If you want to trade group members, talk to me FIRST • Where to do it • Lab down the hall – OSS 428 • When to do it • I’ll set up a schedule • OR – do it on your own time if you have card access R. Smith - University of St Thomas - Minnesota

Recap • Wireless LANs - recap • Link Encryption – book style • Link encryption – LAN style • WEP • WPA • Clipper and Escrowed Encryption R. Smith - University of St Thomas - Minnesota

Protocols and Layers • We use layering for several things • Organize the software • Format the packets • What it really does: Establish a relationship between software components on different computers • Layers communicate with each other at same layer • IP – IP or TCP – TCP or HTTP – HTTP • They ‘use’ the lower layers to carry their messages R. Smith - University of St Thomas - Minnesota

Protocol Layering Examples • Network class – bear with me • Pizza delivery example • How do we order pizza at a party? R. Smith - University of St Thomas - Minnesota

Network Protocol Layering Usually a ‘funnel’ shape • Top level = Applications • Lots of choices: e-mail, web, file exchange, • Uses ‘socket interface’ to talk to networks • Mid levels = “The Protocol Stack” • Transport layer: UDP/TCP • Internet layer: IP • Link layer: LAN protocols • Bottom level = device driver connections • Hardware-specific software, configuration • Uses device driver interface to link to the protocol stack • Uses a cable or antenna to link to the network R. Smith - University of St Thomas - Minnesota

Packets follow the layers • Upper layer data = innermoust • Lower layer data = outermost • Innermost data usually travels the network unchanged • Outermost data gets swapped with each hop through a router R. Smith - University of St Thomas - Minnesota

Addressing • Reachability => what address you have • Layer 2 addresses can’t traverse Layer 3 R. Smith - University of St Thomas - Minnesota

A Routing Exercise • LAN 1: hosts A, B, C • LAN 2: hosts D, E, F • LAN 3: hosts G, H, I • Layer 3 Router connects LANs 1 and 2 • Given MAC addresses • Can A reach: C, D, F, H • Can G reach I, D, A • Given IP addresses • Answer above questions again R. Smith - University of St Thomas - Minnesota

The Network Security Problem • Protection is usually local • Network data travels to remote locations R. Smith - University of St Thomas - Minnesota

Risk: Eavesdropping • An established social tradition (“party lines”) R. Smith - University of St Thomas - Minnesota

Risk: Forgery • Who really sent the message? R. Smith - University of St Thomas - Minnesota

Risk: Replay • If a message worked once, why not again, • and again? R. Smith - University of St Thomas - Minnesota

How do we fix this? • Again, it depends on policy • What are we really trying to achieve (“the big picture”) • What are the real risks to that big picture? • Practical networking choices • Should/must the users control the defenses? • Can/should they choose what gets protected? • Can we isolate the users in a safe but restrictive “bubble”? • If not, what access do they need to the ‘outside’? • What external, secure connections do we need? • Are they ad-hoc, or can we anticipate them? • Risk Assessment • Which threats matter: eavesdropping, forgery, replay? R. Smith - University of St Thomas - Minnesota

Security and the Protocol Stack Application • We get different results by putting protection in different places in the protocol architecture TCP/UDP Layer Protocol Stack IP Layer Link Layer Device Driver R. Smith - University of St Thomas - Minnesota

Security and the Protocol Stack PGP Classic layer-oriented examples of crypto protocols • Application: PGP • encrypts application data • Trans->App: SSL • encrypts the connection • IP->Transport: IPSEC • encrypts routable packets • Link Level: WEP/WPA • encrypts LAN packets Application SSL TCP/UDP Layer IPSEC Protocol Stack IP Layer Link Layer Device Driver WEP/WPA R. Smith - University of St Thomas - Minnesota

How Crypto works in the stack • “Above” a crypto layer • Data is assumed to be in plaintext form • “At” a crypto layer • We convert between plaintext and ciphertext • We have access to some keys • We generate some plaintext headers • Some header info may be encrypted or protected otherwise • “Below” the crypto layer • New network headers are added in plaintext R. Smith - University of St Thomas - Minnesota

How it works Geographically • Application layer encryption • “End to end security” – routable, and inaccessible to others • Defeats intermediate virus scans, intrusion detection • Applied at the discretion of the end user (usually) • Socket layer encryption • Application-application security – similar to application layer • Often applied automatically under control of the server • Sometimes it is a user-level option • IPSEC – IP Security Protocols • Internet layer security – protects routable packets, per-packet • Protects all Internet application traffic equally • Often a substitute for inter-site leased lines R. Smith - University of St Thomas - Minnesota

Diagramming the Crypto • Elements • Protocol stack elements • Where the crypto goes • What is encrypted • What is plaintext R. Smith - University of St Thomas - Minnesota

Let’s visit the lab • It’s down the hall R. Smith - University of St Thomas - Minnesota

That’s it • Questions? Creative Commons License This work is licensed under the Creative Commons Attribution-Share Alike 3.0 United States License. To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/3.0/us/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA. R. Smith - University of St Thomas - Minnesota

CISC 210 - Class Today