How do you validate a binary key / file from a Key Generator

[Nickneem]

I made a key generator according to the specs of a shareware partner so
customers can register online.

It generates a key from a 'secret' and a combination of name and email
/ zip and then encrypts with the md5 algorithm.
This shareware partner sends the key file in an email to the customer.

I'm sorry to ask this perhaps 'stupid' question but:

How do I check on my application side if the licence file / bin file is
valid?
I guess it's considering the reverse engineer risk pretty useless to
make a
function like:

Private Sub ReadLicenseFile()
......GetBytes("MySecret" + txtName.Text + txtEmail.Text + txtZip.Text)
and reverse the encryption.
I guess reversing isn't even possible with the one way
md5 encryption, so how do you verify you got the right key?

I don't want to include 'my secret' hard coded in my code obfuscated or
not...

My previouw application had a text key but in 2 days that key was:
'astalavista.box baby'...

I can use all the help I can get!

Regards,

Michael

 

[Andrew Kirillov]

Hello



First of all, MD5 is not encryption algorithm you mentioned. It's a hash
function.



So, the obvious way it to request from customer "Name", "Company" and other
information and generate a key using some kind of hash algorithm or their
combination, and give the key back to user. The user will input the same
registration data and the key in your program. Your application will
calculate key using the same algorithm as you and compare these keys.



But, it is not a very big problem to create a key generator for your
application if it's written using .NET language.



Search on google. There are some commercial products for guarding you
application.

 

[Nickneem]

Thanks Andrew,

Works like a charm now!
Thanks for you assistance

Michael