IM NTU Distributed Information Systems 2004 Security -- 1 Security Yih-Kuen Tsay Dept. of Information Management National Taiwan University

IM NTU Distributed Information Systems 2004 Security -- 2 Introduction Security Needs –Secrecy, integrity, etc. –Arise from the desire to share resources Security Policies –Specify who are authorized to access what resources –Independent of the technology used Security Mechanisms –Enforce security policies Security Models –Help understand and analyze the above

IM NTU Distributed Information Systems 2004 Security -- 3 Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. The Evolution of Security Needs

IM NTU Distributed Information Systems 2004 Security -- 4 Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. Components of a Security Model

IM NTU Distributed Information Systems 2004 Security -- 5 Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. The Enemy in Network Security

IM NTU Distributed Information Systems 2004 Security -- 6 Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. Familiar Names in the Security Literature

IM NTU Distributed Information Systems 2004 Security -- 7 Classes of Security Threats Leakage –Acquisition of information by unauthorized parties Tampering (Modification) –Unauthorized alteration of information Vandalism –Interference with the proper operation without gain to the perpetrator

IM NTU Distributed Information Systems 2004 Security -- 8 Methods of Attack Eavesdropping –Release of message contents and traffic analysis Masquerading Message Tampering (Modification) –Man-in-the-middle attack Replaying Denial of Service Mobile Code

IM NTU Distributed Information Systems 2004 Security -- 9 Designing Secure Systems Use best standards available Informal analysis and checks Formal validation Security logs and auditing

IM NTU Distributed Information Systems 2004 Security Security Requirements Secrecy (Confidentiality) Data Integrity Authentication Non-repudiation Availability …

IM NTU Distributed Information Systems 2004 Security Source: W. Stallings, “Cryptography and Network Security” The Secret-Key Encryption Model

IM NTU Distributed Information Systems 2004 Security Source: W. Stallings, “Cryptography and Network Security” The Public-Key Encryption Model

IM NTU Distributed Information Systems 2004 Security Source: W. Stallings, “Cryptography and Network Security” The Public-Key Authentication Model

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. Notational Conventions

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. Performance of Cryptographic Algorithms

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. A Scheme of Cipher Block Chaining

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. A Stream Cipher

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. Digital Signatures with Secret Keys

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. Digital Signatures with Public Keys

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. Alice’s Bank Account Certificate

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. A Public Key Certificate of Bob’s Bank

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. The Needham-Schroeder Authentication Protocol

IM NTU Distributed Information Systems 2004 Security Kerberos Developed at MIT For protecting networked services Based on the Needham-Schroeder protocol Current version: Kerberos Version 5 Source code available Also used in OSF DCE, Windows 2000,...

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. Kerberos Architecture

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. The Kerberos Protocol

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. auth(C) contains C,t. ticket(C,S) contains C,S,t 1,t 2,K CS. The Kerberos Protocol (cont.)

IM NTU Distributed Information Systems 2004 Security The Secure Sockets Layer (SSL) Originated by Netscape, now a nonproprietary standard (SSLv3) Provides secure end-to-end communications Operates between TCP/IP (or any other reliable transport protocol) and the application Built into most browsers and servers

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. The SSL Protocol Stack

IM NTU Distributed Information Systems 2004 Security How SSL Works Sessions between a client and a server are established by the Handshake Protocol A session defines a set of security parameters, including peer certificate, cipher spec, and master secret Multiple connections can be established within a session, each defining further security parameters such as keys for encryption and authentication Security parameters dictate how application data are processed by the SSL Record Protocol into TCP segments

IM NTU Distributed Information Systems 2004 Security Security Functions of SSL Confidentiality: using one of DES, Triple DES, IDEA, RC2, RC4, … Integrity: using MAC with MD5 or SHA-1 Authentication: using X.509v3 digital certificates

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. The SSL Handshake Protocol

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. The SSL Record Protocol

IM NTU Distributed Information Systems 2004 Security Micropayments The price of some goods may be lower than the standard transaction fees Micropayments offer a way for selling small- value products and services Technology providers: eCharge (via phone bills), Qpass (monthly bills), Millicent (prepay electronic cash),...

IM NTU Distributed Information Systems 2004 Security The Millicent Scrip Scheme Scrip is a form of digital cash valid only for a specific vender. Format: Scrip is generated and distributed by brokers.

IM NTU Distributed Information Systems 2004 Security Source: G. Coulouris et al., Distributed Systems: Concepts and Design, Third Edition. Millicent Architecture