Hi Romuald, I hope, I am right in that you want to convert a customers name into a unique serial number? If so, do the following
X is string = "Software Buyers & Pinchers Ltd."
Sum is long int = 0
FOR I = 1 TO LENGTH(X)
Sum = Sum + Asc(Middle(X, I, 1))
END
You'd end up with a unique number stored in Sum but there's quite a lot of names fitting that number. So we'd have to make our number a little more 'unique'. Just an example:
Sum = Sum + Asc(Middle(X, I, 1))*I
This way we bind position and value. Even large text-fields would boil down to relatively small Sums (=serial numbers). However, in order to prevent finding out, you should allow a certain minimum length of X only. Short strings will enable a hacker to guess the number more easily. Of course, there are a lot of ways to improve on the algorithm, f.i. Sum = Sum + Asc(Middle(X, I, 1))*I + I\2 (fyi: the '\' is right, this's an integer division in WD like in many BASICs)
Maybe, you think 'Asc' alone is too simple. Make it a binary exclusive OR with a random text exactly as long as the longest string could be.
Every algorithm for calculating a serial number can be broken, it's just a question of the effort put into breaking. So, your algorithm will depend on the price of the program and other influencing facts ..
We did go into this and found out that WinDev is much more secure than any compiled language. The source is in the delivered exe, but it's p-code there, not machine language which could be disassembled easily.
Best regards,
Guenter