SafeNet Sentinel, Руководство разработчика

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Chapter 7 – Implementing Secure Licensing
152 Sentinel Hardware Keys Developer’s Guide
Add Noise to your Query Checks
Generate random queries and then dismiss the results. This generates a
large amount of unused data among the useful data. Anyone trying to
record your communications with the key will need to record large amounts
of data and have trouble deciphering what is meaningful.
Generate New Tables Frequently
Each time you create an update to your application, regenerate the query/
response table. If an attacker has been able to record all the challenges used
by your program, the update will suddenly require this work to be repeated.
If you have used the tips discussed above, it will likely be time consuming so
the illegitimate user is stuck using outdated software.
Specify Cheat Counter Value
You can specify a cheat counter value only for non-RTC Sentinel Keys.
The cheat counter value is global to the Sentinel Key. It applies to all the fea-
tures having lease attribute enabled. You can specify a the cheat counter
value right before programming hardware keys in the
License Manager
screen.
If desired, you can use the Secure Update process to increment the cheat
counter in the field.
Note: You should call the SFNTQueryFeature function in your application code to
detect time tampering. In addition, the SFNTEncrypt, SFNTDecrypt, SFN-
TSign, and SFNTGetDeviceInfo functions also check for system time tam-
pering.
Use AES Algorithm to Encrypt Data
You can use the AES algorithm present in the Sentinel Key for encrypting
16-byte data blocks. AES has withstood intense scrutiny from the cryptog-
raphy experts and is adopted by National Institute of Standards and
Technology (NIST) as US FIPS PUB 197 in November 2001 (after a 5-year