Any Idea for a Challenge/Respone algorithm?

[callidus2000]

Hi,

I need some help/an idea for a challenge/response solution (I miss the forrest for the trees).

I've got to develop a programm which installs some license information onto an computer (a MAK Key for Win7). The installation is not the problem, but I don't want this MAK installer to be missused, so I want to

• create some machine specific challenge code
• create a text file [sysinfo] which contains the challenge and some information about the computer (e.g. brand, modell, network configuration)
• encrypt the sysinfo with gnupg to a specific destination key (identified by the fingerprint)
• let the user send the sysinfo to a service team
• the service team
  • decrypts the sysinfo
  • checks all data
  • puts the challenge into a secondary programm
  • this creates a response code which is send to the original user
• with the correct response code the MAK installer does it's magic

Is there any existing aproach which my forum searches did not uncover? Especially for the Challenge/Response.

-Callidus2000

[twitchyliquid64]

It appears like you want to use public key cryptography. Take a look at the OpenSSL library, or look at the windows crypto API.

The program needs to have a hard coded public key, and your service team needs to have the private key.

Your response needs to be encrypted with the private key. The client will decrypt it with the public key, and thus knows that the signal to activate the software is valid.

This is not simple, and there is no established autoit code for doing this.