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mode trial or serial number

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pink on 21 Jul 2011
is there a code that can be used for the application (gui) can function for 30 days or whether it can provide an example to make an application to embed serial numbers?

Answers (2)

Jan on 21 Jul 2011
This has been discussed repeatedly. If your program is cheap and large (< 10.000$, > 10.000 lines), P-coding is a fairly secure encryption method. Checking the date ("if now > datenum('23-Aug-2011')...") is easy to break by overloading the command NOW. "builtin('now')" is one step more secure, but even BUILTIN can be overloaded and the system clock can be manipulated also.
As next step the client computer could contact a server in the internet to check the date. But this communication can be manipulated also, therefore Walter talked of aquantum encryption. Anyhow, if your program is not too expensive (< 10.000.000$), an AES enctrypted communication should be sufficient. But then the P-coding will be the weakest point again.
This page shows some methods to create a serial number: Undocumented: ComputerID. All these numbers can be manipulated.
I assume a printed and signed non-disclosure-agreement is the best protection.
Jan on 24 Jul 2011
@Walter: I still do not get the feeling, that there is a scientific or professional approach for protecting important data. The magic keys are still saved in clear text in the memory, the 3DES encrypted bank transferes can be redirected by silly skimming attacs, famous software packages do still use the harddisk ID to identify a machine and the secret documents can by copied in TerraBytes from the Pentagon. Are you really sure that there is any graduate level university course and if so, where do the students go?!

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Walter Roberson
Walter Roberson on 21 Jul 2011
What level of certainty do you need? This task is very very difficult to do robustly if the user is more than 12 km away from the server (the current practical distance limit for quantum cryptography; recently extended to 20 km in specialized optical fibres, but that is not in production yet.)
pink on 22 Jul 2011
I just want to learn the basics of an application protection system.

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