Absolute Date Restrictions

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Absolute Date Restriction expires a license key on a specific date. For example: 2005-10-01 expires the license when the date if GREATER than October 1, 2005. The user's local time zone is used to determine if this date has been reached.

Typically absolute date restrictions are used to:

1.	Sell Software Licenses on an monthly or annual basis. When the license expires, you can issue a new key to subscribing customers.

2.	Protect against disk re-imaging or trial marker clearing. By setting an absolute date when your trial software no longer works, you make it difficult for users to bypass license termination.

Dates supplied to Thinstall (command-line key generator or GUI) are always in the format of :

YYYY - MM - DD

YYYY = Four digit year, must be between 2003-2258
MM = two digit month (01 = January, 12=December)
DD = two digit day of month

Note: The month and day must always be 2 digits



Setting an absolute time restriction
Using the Thinstall GUI, you can set an absolute time restriction for the default license key as well as for generated license keys.

GUI Version:
Menu -> Link -> License System / Trial Demo -> License System Version 2 (Default Key / Generate Key)



Command-line Key Generator

th_keygen2 my_password -expire_on 2005-10-01


Accesing Information in your program

The Environment Variable TS_EXPDATE provides information about this restriction to your program.
Click here for more information about License System Environment Variables.


Issuing Multiple Keys

You can issue multiple keys that have absolute time restrictions. When the user enters a new key, it becomes the "current key" and its absolute date restriction will apply. This allows you to issue a new key monthly or annually that has a new absolute date expiration. When the user enters the new keys provided, they will be able to continue using the software uninterrupted.


Security Concerns with Relative Time Restrictions

Clock Set-backs: Thinstall will automatically detect if the user tries to set their clock back. If this situation is detected the current license key will remain expired until the clock is restored.

Disk Re-imaging:

It is possible to "re-image" a computer's hard drive so that the entire hard drive is restored to the state before your license key was first used. An absolute date restriction provides fairly good protection against this, however it is still possible to set the system clock back at the same time as disk-re-imaging to thwart absolute date restrictions. The combination of having to continously re-image the hard drive and work with an incorrect clock should prevent 99.9% of attempts.