Sentinel Hardware Keys Developer's Guide - Customer Connection ...

Chapter 7 – Implementing Secure Licensing
Contents Glossary Index Troubleshooting
SFNTVerify Operation
178 Sentinel Hardware Keys Developer’s Guide
You may even sign part of your application data (such as constants) and verify
its integrity before you use it. You can implement a similar signature
verification scheme for your digital content (such as, text files and images)
and store the 42-bit signature as raw data in the Sentinel Key memory.
Decentralize Your Security Checks
Decentralizing the security checks throughout the code is a good practice.
This requires each place in the code to be modified in order for the application
to run without the key. Restricting them to a few places can lead to easy
detection and elimination subsequently. Given below are more tips:
Use In-line Functions in Place of a Centralized Function
Creating a single function call that checks the key and then making function
calls throughout the code does not decentralize. Instead, only the
security check function must be modified to operate without the key.
Use Many Different Security Checks
If you use the same security check in many places of the code, then you can
find each check by searching for patterns.
Tip: Place the security checks in hard-to-trace operations. For example, if you
scatter you check throughout a series of database operations, it can be
extremely time consuming to trace the calls.