Host Security Review and Physical Keys

1. Host Security Reviewand Physical Keys Cyber Security Spring ‘05

2. First portion of course • Access control • Discretionary ACL’s in Windows • Mandatory access control through type enforcement in SELinux • Least privilege • Set UID in Unix/Linux • Explicit privilege manipulation on Windows • Impersonation on Windows

3. Secure Coding • Considered at three levels • Design: e.g., analyze communication algorithms against common attacks like man in the middle • Implementation: e.g., run buffer overflow checking tools. • Operation: e.g., Turn off unnecessary services • Echoes most good software engineering practices or common sense • Checklists can help remind us of these things

4. User Identity • Overview of directories • Unifies information needed by many applications in an enterprise • Source of certificates used by PKI • Not a complete panacea, • Overview of network AAA servers • Integrate authentication with network security enforcement devices • Evolved from Dial up technology • Limited cross device authentication • Xauth mechanism configured on enforcing device can be used to use AAA server for IPSec client authentication • Can redirect authentication to other sources • Will examine in greater detail during the network portion of the course

5. Physical Key Paper • Analysis of master keyed physical locks from a CS perspective. • “Cryptology and Physical Security: Rights Amplification in Master-Keyed Mechanical Locks”, Matt Blaze, http://webtools.uiuc.edu/survey/NonSecureSurvey?id=9931496

6. Pin Tumbler Keys • Most common type of keys • Key cylinder is held in place by a number of pins • P which ranges from 4 to 7 • In a single keyed lock each pin is cut in one of D locations • D ranges from 4 to 10 • The key is correspondingly cut. Inserting the right key pushes up the pins so the cut part matches the cylinder. • P^D possible keys

7. Master Keys • In many environments, there is a master key that opens all doors • Or there can be a hierarchy of master keys • The master key that opens all locks is called the Total Master Key (TMK) • In a master key scenario, each pin is cut in two places • One set of cuts occur in all locks in the installation

8. The problem • Create a master key from an ordinary key and lock in the system • Assume your have access to key blanks and appropriate key cutting devices • And some privacy

9. The key insight • Cross keys • While the design intended only keys that match the master cutting or the specific cutting, keys with a combination of both cuttings will work on your example lock • You can test each bit in isolation • Moving from a P^D problem to a P*D problem.

10. The algorithm • Take a blank, and cut P-1 of the bits to the bitting of the custom key. • For the P’th bit, create D-1 keys that try all cuts except the one of the custom key • Or just start with shallowest cut and re-cut the same physical key • The one that works has the correct cut for that bit on the TMK • Do the same thing for all P bits • Don’t do this at home….