Security and Trust By Troy Lee

Overview Security Design Principles Architectural Access Control Access Control Models Connector-centric Architectural Access Control Distributed Security Protection Against Piracy Trust Management Trust Trust Model Reputation-Based Systems Architectural Approach to Decentralized Trust Management

Computer Security “The protection afforded to an automated information system in order to attain the applicable objectives of preserving the integrity, availability, and confidentiality of information system resources (includes hardware, software, firmware, information/data, and telecommunications).” – National Institute of Standards and Technology

3 Main Aspects Confidentiality (aka Secrecy) Integrity Availability

Confidentiality Preventing unauthorized parties from accessing the information or perhaps even being aware of the existence of the information

Cryptography Equations Cipher = Encryption Function(Encryption_Key, ClearText) ClearText = Decryption Function(Decryption_Key, Cipher) 2 Forms Shared-Key Cryptography Public-Key Cryptography Best Practices Evaluate Performance, Architecture, and Security Requirements Choose a Suitable Public Algorithm Use Frequently Changing Keys as the Primary Secrecy Mechanism

Integrity Only authorized parties can manipulate the information and do so only in authorized ways

Availability Accessible by authorized parties on all appropriate occasions

Design Principles Least Privilege Fail-Safe Defaults Economy of Mechanism Complete Mediation Open Design Separation of Privilege Least Common Mechanism Psychological Acceptability Defense in Depth

Architectural Access Control Access Control Models Connector-Centric Architectural Access Control

Access Control Models Classic Discretionary Access Control Role-Based Access Control Mandatory Access Control

Connector-Centric Architectural Access Control Basic Concepts Central Role of Architectural Connectors Algorithm to Check Architectural Access Control Integrating Security in ASTER

Basic Concepts Subject Principal Resource Permission Privilege Safeguard

Central Role of Architectural Connectors Components Connectors Secure Architecture Description Language

Secure xADL

Algorithm to Check Architectural Access Control

Secure Cooperation

Firefox

Integrating Security in ASTER

Distributed Security

Protection Against Piracy Goals Raise Cost of Breaking Protection Mechanism Increase Probability of Being Caught Discourage Attempts at Piracy Technologies Hardware and Software Tokens Water Marking Code Partitioning

Trust Management Trust Trust Model Reputation-Based Systems Architectural Approach to Decentralized Trust Management

Trust “A particular level of the subjective probability with which an agent assesses that another agent or group of agents will perform a particular action, both before he can monitor such action (or independently of his capacity ever to be able to monitor it) and in a context in which it affects his own action” – Diego Gambetta

Trust Model Describes the trust information that is used to establish trust relationships, how that trust information is obtained, how that trust information is combined to determine trustworthiness, and how that trust information is modified in response to personal and reported experiences

Reputation-Based Systems Types Decentralized Centralized Examples Ebay XREP

Phase 1 – Resource Searching Phase 2 – Resource Selection and Vote Polling Phase 3 – Vote Evaluation Phase 4 – Best Servent Check Phase 5 – Resource Downloading

Phase 1

Phase 2

Phase 3

Phase 4

Phase 5

Architectural Approach to Decentralized Trust Management Threats Measures to Address Threats Guidelines to Incorporate into an Architectural Style Resultant Architectural Style PACE Architectural Style PACE-Based Trust-Enabled Decentralized File-Sharing App

Threats Impersonation Fraudulent Actions Misrepresentation Collusion Denial of Service Addition of Unknowns Deciding Whom to Trust Out-of-Band Knowledge

Measures to Address Threats Use of Authentication Separation of Internal Beliefs and Externally Reported Information Making Trust Relationships Explicit Comparable Trust

Guidelines to Incorporate into an Architectural Style Digital Identities Separation of Internal and External Data Making Trust Visible Expression of Trust

Resultant Architectural Style Functional Units Communication Information Trust Application

PACE Architectural Style

PACE-Based Trust-Enabled Decentralized File-Sharing App

Summary Security Design Principles Architectural Access Control Access Control Models Connector-centric Architectural Access Control Protection Against Piracy Trust Management Trust Trust Model Reputation-Based Systems Architectural Approach to Decentralized Trust Management

References Bidan, C., and V. Issarny. Security Benefits from Software Architecture. Web. 7 Apr Devanbu, Premkumar T., and Stuart Stubblebine. Software Engineering for Security: A Roadmap Web. 7 Apr Nagaratnam, Nataraj, Philippe Janson, John Dayka, Anthony Nadalin, Frank Siebenlist, Von Welch, Ian Foster, and Steve Tuecke. The Security Architecture for Open Grid Services. 17 July Web. 7 Apr Taylor, Richard N., Nenad Medvidovic, and Eric M. Dashofy. Software Architecture: Foundations, Theory, and Practice. Hoboken, NJ: Wiley, Print.