@Yuan Xue ([email protected]) Network Security Review and Beyond Network Security.

@Yuan Xue ([email protected])

Network Security Reviewand Beyond Network

Security


From a Computer to InternetBuilding a network of global scale Start from a collection of computers Direct link network internetwork

Transport layer connectionless v.s. connection-oriented

Network protocol stack

Internet

Link

IP

TCP/UDP

Application

Link

IP

TCP/UDP

Application

Link

IP

Link

IP


From a Computer to InternetSecurity issues Single computer Networking environment

Secure communication in a public environment Computer system security with remote access

Internet

Link

IP

TCP/UDP

Application

Link

IP

TCP/UDP

Application

Link

IP

Link

IP


Security GoalsGoals

Confidentiality Data and traffic

Integrity Data integrity (Data

authentication ) Origin Integrity (Source

Authentication) Peer authentication and data

origin authentication Non-repudiation

Source and Destination Availability

Mechanisms Authentication Access control Encryption Data integrity protection & Digital

Signature Traffic control

Routing, padding

Internet

Link

IP

TCP/UDP

Application

Link

IP

TCP/UDP

Application

Link

IP

Link

IP


Security Mechanisms

This course -- Network Security Cryptographic Approach

Encryption Data integrity protection & Digital Signature Authentication

Network Approach Traffic control

System Approach Intrusion detection systems Firewall

System Security Authentication Access Control (Authorization) Multi-level Security

Program Security

Security issues Single computer Networking environment

Secure communication in a public environment Computer system security with remote access

Mechanisms Authentication Access control Encryption Data integrity protection & Digital

Signature Traffic control

Routing, padding

Methodology Examine all possible

vulnerabilities of the system Consider available

countermeasures.


DSS

SHACBC

Confidentiality

Symmetric encryption algorithm –Block ciphere.g., DES, 3DES, AES

Asymmetric encryption algorithm –Block ciphere.g., RSA, ECC

Modes of operation (block stream)

Symmetric encryption algorithm -- Stream ciphere.g., RC4

Asymmetric key algorithm – key exchange, e.g., Diffie-Hellman

Asymmetric key algorithm -- digital signature e.g., DSA

MAC Hash function

Key establishment

IntegrityData integrity + source

authentication

HMAC

Non-repudiation


From Principle to Practice

Application/Transport layer based solutions

Secure network-based applications Web – SSL, transportation layer solution Email – PGP, application layer solution

Secure network + support for application

IPsec Internet Security

BGP security Wireless Security

IEEE 802.11 security

Link

Network

Transport

ApplicationPGP

SSL

WEP, WPA, IEEE 802.11i

IPSec


Put things together

GPG


SSL (I)Services

Confidentiality – symmetric encryption Message Integrity – MAC

Application data

fragment

fragment MAC

Encrypted

compress

EncryptedSSL record header

•Content type•Version•Compressed length


Alice Bob

I want to talk to you, RAlice

Certificate, RBob

E(KUbob,S)

Secure communicationvia keys derived from K

E(KUbob,S)

Certificate, RBob

Secure communicationvia keys derived from K

SSL (II)


IPSec

Transport mode Encrypts the payload data from upper-layer protocol IP header in clear text

Tunnel-mode Encrypts the entire IP packets including the IP header Adding a new IP header

IP headerEncrypted

data payload

NewIP header IP

headerdata

payload

Encrypted

IPSec header


BGPOverview

AS: Internet routers are grouped into management domains called Autonomous Systems (AS).

BGP: Routing information between AS is exchanged via BGP UPDATE messages.

Threat BGP does not have any security protection over routing

information, for example: Routing information source authentication UPDATE message integrity protection

If malicious attacker injects or modifies routing information (UPDATE messages), BPG routing will be interrupted and packets will get dropped.


S-BGPThree security mechanisms are employed

Public Key Infrastructure (PKI) is used to support the authentication of AS's identity, and BGP router's identity.

BGP transitive path attribute is employed to carry digital signatures covering the routing information in a BGP UPDATE message.

IPsec is used to provide data and partial sequence integrity, and to enable BGP routers to authenticate each other for exchanges of BGP control traffic.

Further reading Stephen Kent, Charles Lynn, and Karen Seo, Secure Border Gateway

Protocol (Secure-BGP), IEEE Journal on Selected Areas in Communications Vol. 18, No. 4, April 2000, pp. 582-592

Stephen Kent, Charles Lynn, J. Mikkelson, and Karen Seo, Secure Border Gateway Protocol (S-BGP) -- Real World Performance and Deployment Issues, in ISOC Symposium on Network and Distributed System Security, 2000.


Security in Wireless LANWEP (Wireless Equivalent Privacy)

a link-level security mechanism defined in IEEE 802.11 Stream cipher RC4 used in a nonstandard way

A base key is concatenated with a 24-bit per-packet nonce, and is used as a per-packet RC4 key.

CRC checksum is used for integrity protectionFluher, Mantin, and Shamir Attack

An eavesdropping can deduce the base RC4 key based on several millions encrypted packets whose first byte of plaintext is known.

Stubblefield, Ioannidis, and Rubin demonstrated its feasibilityProblems with WEP: A summary

24-bit IVs are too short to provide confidentiality CRC checksum is insecure, and can not protect packet integrity The way that IV is combined with the key is subject to cryptanalysis.

Passive eavesdroppers can learn the key after observing a few million encrypted packets

Lack of source and destination address authentication


Improved 802.11i Architecture

Stage 1: Network and security capability discovery

Stage 2: 802.1X authentication and key establishment (mutual authentication, establish shared secret, ciphersuite)

Stage 3: Secure association (management frames protected)

Stage 4: Four-way handshake (master key confirmation, session key derivation,

group key distribution)

Stage 5: Group key handshake

Stage 6: Secure data communications

802.1X failure

Association failure

Four-way handshake timeout

Group key handshake timeout

Invalid MIC or other security failures

Security Analysis and Improvements for IEEE 802.11i, He and Mitchell, NDSS05


Web Security

Authentication of Web ServiceCookiesScripts Java Scripts XSS

SQL injectionActive X


Worm& DoS

Availability Issues

Probe rate of Code red worm(a typical random-scanning worm)

Probes of Slammer worm from Dshield data set• Initially matched random scanning worm• Soon slowed down due to bw saturation and network failures


Firewall & IDSDeployment

InternetSMTP

HTTP

FTP

TELNET

Packet filter Application gateway

@Yuan Xue ([email protected]) Network Security Review and Beyond Network Security.

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