Why Cryptosystems Fail Ross Anderson

1. Why Cryptosystems FailRoss Anderson Presented by Su Zhang

2. Main Idea • Wrong assumption causes bad consequences • What is the true case? • Most losses are caused by implementation errors and management failures.

3. Differences Between Cyber And Real Security • Real life security: • Has strong organized learning mechanism. • Governmental cryptosystem: • No such good schema because some secrecy involved.

4. How ATM Fraud Takes - Bad Insiders • (dismissed employees with evil minds) • Two incidents (stealing cards and PINs ) per business day.

5. How ATM Fraud Takes - Black-hearted Outsiders • Peeper • Jackpotting (Intercepting pay response from ATM) • ATM bug --- Believe the card inserted is the same as the previous card.

6. How ATM Fraud Takes – Exploit ATM “Vulnerabilities” • Naïve offline ATMs procedure • e.g. first + third = second +fourth • Issuing only three different PINs to all users. • Stupid squared cardboard • Dramatically reduced the decryption complexity (from 1/3000 to 1/8).

7. Stored Encrypted PIN in a Database • Programmer can get another card’s PIN by searching his encrypted PIN in the Database. • Wrote encrypted PIN into magnetic strip • Bad guys can only change their card number into the target number. • Mitigation:Encrypt the combination of account number and its PIN.

8. How ATM Encryption Works

9. Problems With Encryption Products • PIN keys can be found easily. • Soft/Hardware compatibility issue. • Not all security products are good. • Hard to get qualified maintainers.

10. Cryptanalysis Threats Need to be Considered • Home-grown encryption algorithms. • Weak parameters. • e.g. RSA keys are too “short” to be secure. • Weak algorithms – DES. • Hardware custodians could misuse it for private gain.

11. Risks From Bankers • Two key components holder may conspire to steal money. • Need more effort on quality control. • Lack of audit processes.

12. Equipment Vendors’ Issues • Specialized security expertise need to be spread. • User need to understand how to use the high level product. • Vendor should keep their eyes on all of the time. • Attacks may be launched after several years “hibernate”. • Sloppy quality control. • Products are not carefully examined.

13. What Required to Mitigate These Issues? • Classify different levels of users • e.g. beginner, professional, expert, etc. • Design an integrated application. • Provide training service to client personnel. • Provide their own experts for maintaining.

14. Why Provider Misjudged Users’ Ability? • The networking during early days is limited. • Internal, external even abroad disputed transitions need to be considered. • Human factors. • e.g. Audit department personnel dislike security group because they will “bring” them more work. • Security teams didn’t last too long. • Managers don’t like to be specialized in security for fear that will affect their career track.

15. Confirmation -Military Department is Suffering the Same Problems • Most security failures are at implementation level. • They are not cleverer but they are more concerned on security issues. • The threat profiles developed by the NSA for its own use are classified . • They put more effort on quality control. But still need more investment.

16. One Possible New Paradigm (Inspired by Safety Critical System) • List all possible failure modes. • Make clear preventing strategies. • Explain in detail how these strategies are implemented. • Make sure equipments are operated by right people. • Auto process system.

17. Conclusion • Why security failed? • Implementation errors. • Management errors. • System and human factors. • Consequence: Security paradigms have mixed some software engineering ideas.