Security Engineering, 3rd Edition

CHAPTER 16Security Printing and Seals

A seal is only as good as the man in whose briefcase it's carried.

– KAREN SPÄRCK JONES

You can't make something secure if you don't know how to break it.

– MARC WEBER TOBIAS

16.1 Introduction

Many computer systems rely to some extent on secure printing, packaging and seals to guarantee important aspects of their protection.

• Most security products can be defeated if the opponent can get at them before you install them. Seals, and tamper-evident packaging generally, can help with trusted distribution, that is, assuring the user that the product hasn't been tampered with since leaving the factory.
• We saw how monitoring systems, such as utility meters and tachographs, often use seals to make it harder for users to tamper with input. No matter how sophisticated the cryptography, a defeat for the seals can be a defeat for the system.
• I also discussed how the contactless cards used in most building entry control systems can be cloned, thanks to the attacks on Mifare and some of its successors. If you're scrutinising the ID of an engineer before you let him into your hosting centre, it can be a good idea to eyeball the ID as well as reading it electronically. Even with electronic ID cards, the security printing can still matter.
• In general, it may be a more realistic goal to make credentials tamper evident rather than tamper proof: if someone dismantles their smartcard and gets the keys out, they should not be able to reassemble it into ...