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New Checksum Feature Not Sticking

 
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KSoft



Joined: 26 Sep 2006
Posts: 19

PostPosted: Mon Jan 29, 2007 10:41 pm    Post subject: New Checksum Feature Not Sticking Reply with quote

I just upgraded to the 3.4.0 version and notice that the check in the "Include Product Info Checksum" box doesn't stick when I edit a product, click it, and press OK.

I'm using the product info to include a "licensed to" section so my product info data will almost always be longer than 7 characters.

Does this new checksum feature negate the recommendation in the documentation to only use a checksum for longer data? If not, what do you suggest that produces a reliable < 7 character checksums? I have no problem doing that (and not actually embedding the product info in the key). I'm trying to keep the key length as small as possible while maintaining a "licensed to" area..

Thanks!
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Infralution



Joined: 28 Feb 2005
Posts: 5027

PostPosted: Tue Jan 30, 2007 7:05 am    Post subject: Reply with quote

You're right there is an issue there. We should have a fix released tomorrow for this.

The new product info checksum feature is only required if you are embedding more than seven characters worth of data in ProductInfo. In this case you should use it because it ensures that a user entering a longer license key cannot make a mistake which might result a valid license but rubbish in the ProductInfo. For keys with less than 7 characters worth of data in ProductInfo this isn't necessary because the the ProductInfo is validated as part of the decryption process.

If you want to keep your license keys short then the best policy is to calculate your own checksum of your "Licensed to" information and include this in the ProductInfo (without using the ProductInfo checksum). Then have the user enter the "Licensed to" information as clear text and validate that the entered information matches the checksum in the ProductInfo. The custom licensed app sample project shows how to do this.
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KSoft



Joined: 26 Sep 2006
Posts: 19

PostPosted: Tue Jan 30, 2007 1:41 pm    Post subject: Reply with quote

Thanks!

CRC32 produces the smallest checksum that I'm aware of but I'm having an amazing bit of difficulty finding vb.net source to produce a CRC32 checksum. I'll keep looking - and thanks for the upcoming fix!
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Infralution



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PostPosted: Tue Jan 30, 2007 10:35 pm    Post subject: Reply with quote

I should have mentioned that the License class includes a Checksum method that returns a short (3 character) checksum. This obviously isn't as secure as CRC32 - however it really doesn't need to be since the security of the license key is ensured by the RSA validation. The checksum is used to ensure that the user entered data matches that expected.
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KSoft



Joined: 26 Sep 2006
Posts: 19

PostPosted: Tue Jan 30, 2007 10:43 pm    Post subject: Reply with quote

I saw that after I posted here. Thanks!
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PostPosted: Wed Jan 31, 2007 1:04 am    Post subject: Reply with quote

Version 3.4.1 of ILS has now been released fixing the "Include Product Info Checksum" issue in License Tracker.
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