Chris Kite Programming, Computer Security, Etc.

Cracking a Software License Scheme

03.31.2009 · Posted in Cryptography, Security

In his latest blog post, Andy Sloane issued a challenge to create a key-generator for his bespoke software licensing scheme.

Looking through his code, I quickly found that he was using RSA, and that valid keys decrypted to 12345678 under a hardcoded RSA public key.

In my response on the Reddit discussion, I explained creating a keygen was as simple as adding a multiple of his public-key modulus n to an existing key. Others quickly pointed out that it was trivial to factor n because it was not sufficiently large.

This is a great example of why creating secure systems is so hard: implementation mistakes are easy to make, and undermine the security of even the best cryptosystems.

3 Responses to “Cracking a Software License Scheme”

  1. Hello,
    I wonder if you can help me crack a licence.lic file of a program. This program is a server program, and it uses the licence.lic to control expiration time and licenced party. I need to crack these two things. Of course, I will financially compensate your work.
    If you are willing to help me, please reply me. Thanks!
    Yours sincerely,

  2. hai,

    i need help if you can crack soft license (license.lic) of program, may be same need with kevin,
    please contact me by mail, if you are willing o help me.

  3. Hi..

    I need help sama as above. Pls help


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