1. HIRTS DARP ALARP & Software - 1 Unifying Safety and Security John A Clark Senior Lecturer in Critical Systems University of York

2. HIRTS DARP ALARP & Software - 2 Contents What is safety and what is security? Why do we want to unify the two? What’s the Same What’s Different How can we make progress?

3. HIRTS DARP ALARP & Software - 3 Things that are similar Both properties of systems Both risk based integrity levels (e.g. SILs, assurance/confidence levels) Certification authorities. Independent V&V Process development standards. Subject to attack. The concepts have the same word in some languages (Sicherheit, securite)

4. HIRTS DARP ALARP & Software - 4 Things that differ Nature of what we get wrong. How about (traditionally) Safety: we get the requirements wrong. Security: we typically get the implementation wrong. Process development standards Security standards (e.g. ITSEC) place heavy emphasis on top level correctness (with greater informality in refinement). Essentially get the model and top level spec right. Safety standards seem more keen to propagate rigour (formality) through refinement levels.

5. HIRTS DARP ALARP & Software - 5 Things that cause problems ‘People are our greatest asset…’ People are our worst nightmare Human factors issues with safety widely appreciated But with security comes malice

6. HIRTS DARP ALARP & Software - 6 Some things of Interest in Security Confidentiality Integrity Availability Accountability