Transcript Introduction (Pres.)

COEN 350 Network Security
Introduction
Computer Networks
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OSI Reference Model
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Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer
OSI Reference Model
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Useful to establish terminology
Not implemented
Upper layer implemented in terms of
lower layer.
OSI Reference Model
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Application Layer
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Locus of applications that use networking
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P2P
HTTP
ftp
Presentation Layer
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Encodes application data into a canonical form
Decodes it into system-dependent format at the
receiving end.
OSI Reference Model
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Session Layer
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Extra functions over reliable one-to-one
connection
RPC
Transport Layer
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Reliable communication stream between a
pair of systems.
IP, UDP, TCP, ICMP
OSI Reference Model
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Network Layer
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Computes paths across an interconnected
mesh of links and packet switches
Forwards packets over multiple links from
source to destination
OSI Reference Model
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Data Link Layer
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Organizes physical layer’s bits into packets
and controls who on a shared link gets
each packet.
Physical Layer
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Delivers an unstructured stream of bits
across a single link of some sort.
TCP/IP Suite
Protocol Layers and Security
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Security measures often layer network
protocols.
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Protect contents of packages is protection
at layer 2.
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Still allows traffic analysis.
IPSec protects (encrypts) packages at layer
4
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Does not work with NAT.
Goals
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Authentication
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Authorization
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Are you allowed to do that?
Integrity
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Who are you?
Is this the real message?
Privacy
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Does anyone else know about it?
Zone of Control
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The zone that needs to be secured in order to prevent
eavesdropping.
Physical access needs to be prevented.
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Tempest program (US military)
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All computer systems radiate information.
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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:
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Possible to reconstruct image on a monitor from 20 ft.
Need to include backdoor channels like modems, etc.
Tempest: Set of standards for limiting electric or electromagnetic
radiation emanations from electronic equipment.
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Shortcut for filed of compromising emanations / Emissions Security
Legal Issues
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Patent Law
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First inventor has the right to invention.
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Patents issued based on what inventors present regarding
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Novelty (  Prior Art)
Importance (“Aha” effect)
Patent process flawed since Reagan under-funding, but
slowly getting better
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In other countries: First one to file.
Patent decision needs to be made within a day.
Many cryptography algorithms are / were patented.
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Are now moving into the public domain.
Still, many standards are built around patented methods.
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Kerberos uses secret key encryption instead of public key
encryption.
Legal Issues
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Export Control
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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
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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).
Legal Issues
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Key Escrow
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Cryptography algorithms became unbreakable in the
nineties.
Prevent wiretaps, computer forensics, etc.
National security efforts sponsored Clipper:
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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.
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Considered to be almost impossible if cooperation were legal and
impossible if cooperation were illegal.
Government gave up.