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VB.net Security Key

Posted on 2014-01-18
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Last Modified: 2014-01-18
Hi

A few months ago I looked at the following security key generator provided by Eric Moreau

http://www.emoreau.com/Entries/Articles/2007/12/Licensing-a-VBNet-application.aspx

I still don't understand the fundamentals. Could anyone please explain briefly how
this works and what stops multiple people using the same key to install the app on multiple machines?

I don't understand how the following process works "This method is using the registry (the CurrentUser section) to store encrypted information to keep track of everything. Symmetric encryption is used (a single key used to encrypt and decrypt). This demo is using a textbox (titled Pass Phrase) for you to try different combination. "
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Question by:Murray Brown
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LVL 18

Expert Comment

by:Steven Harris
ID: 39791337
I still don't understand the fundamentals. Could anyone please explain briefly how
this works and what stops multiple people using the same key to install the app on multiple machines?
The key that is generated is specific to the machine.  As a quick and dirty example (not specific to the code, but as an example only):

I have a computer that is named "TOS4567890"     <-- string value specific to my PC
You are using a passphrase of "HelloWorld!"     <-- string value only known to you
The generated key is "HTeOlSl4o5W6o7r8l9d0!"     <-- the above two interact to make this (can you see how I combined the two?)

Think of this as the Username/Password combination.  You have to know both in order to gain access.
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Author Comment

by:Murray Brown
ID: 39791363
Thanks. The part that confuses me is that I generate the key on my machine using the middle two boxes. Then I send them the username and password. Am I doing it incorrectly?
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LVL 18

Accepted Solution

by:
Steven Harris earned 1000 total points
ID: 39791396
Remember, the example I gave was not indicative of the code as written, but was in relation to the hashing method. to generate said key.

Other than that, you are assigning the key correctly.  You are both running the same algorithm (you encrypt in your program, they decrypt in their program), so the program can validate that they key is correct.

For the part I missed in your original post:

...what stops multiple people using the same key to install the app on multiple machines?

I have not tested the method myself, but from what I can see:  Nothing.  You would need some type of check in place (like a server) that validates the use of the key and to see if it is already in use.
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LVL 28

Assisted Solution

by:Ark
Ark earned 1000 total points
ID: 39791725
Please see this tutorial
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Author Closing Comment

by:Murray Brown
ID: 39791763
Thanks very much for the advice
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