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Security Distributed Systems Lecture # 14. Why care about security? Authentication Use another person’s ID for sending email Non-repudiation E-commerce.

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Presentation on theme: "Security Distributed Systems Lecture # 14. Why care about security? Authentication Use another person’s ID for sending email Non-repudiation E-commerce."— Presentation transcript:

1 Security Distributed Systems Lecture # 14

2 Why care about security? Authentication Use another person’s ID for sending email Non-repudiation E-commerce Spoof credit card number Replay card transactions Sniff information Monitor the number of transactions or stock-trades Denial of Service Malicious software

3 W32.Blaster.Worm Distributed Denial of Service Blaster Worm replicated itself on 120,000 computers worldwide On August 11, 2003 Microsoft update server was pelted with DDOS Lost out at name indirection Microsoft removed the DNS entry of windowsupdate.com

4 What we want to achieve A secure system must ensure privacy, integrity and availability of resources What constitutes a secure system? What do you think? Policy How the system implements it: Mechanism Design Principle: Don’t overdo security! Tension between usability and security

5 A snapshot of a distributed system Illegal Access Password hacking Spoofing/sniffing Tampering Replaying Illegal Access Denial of service Virus: Byzantine failures

6 Design space Networks are insecure Interfaces are externally visible Names are well-known

7 Security Threats Masquerading: Using someone else’s ID Eavesdropping: Spoof data Tampering: Spoof and modify data Replaying: Sniff and replay Denial of Service: Hoard available resources

8 Common techniques for security Encryption Sender identity? Message integrity? Signatures: non-repudiation Checksums: integrity Authentication: access control Time-stamping: replay attacks Logging: traceback

9 Code level security Pointers Turing completeness Modularity Type checking Code validity

10 Design Principles Analyze Threat level Typically lazy/silly users Minimize Trusted kernel Log events Limit the scope and time of security tokens Publish algorithms Security by tokens

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