17 replies to this topic

[reniery]

Hey guys

So I have a a VB App I made, and I made sure to protect it using license keys, so no one but people who pay me can use it :)

Now what im trying to do , is create a demo license so people can try my app and see if its useful for them.
What I want to do is kinda like shareware, so when X days have passed the program should tell the user that the trial is over

So how would I do this

[Xav]

Well, create a new type of license key, which might store the remaining days (or the end date) in some encrypted file, perhaps in the Registry. Then, when the program loads, tell it to check the value. If the trial is up, display a message/link to buy, and close the window again. If not, run as normal.

[reniery]

Thats what I did, I stored the key in the registry and then my program checks the encrypted date to see if its valid.
The thing is I compare the encrypted date with the system date so if the user changes the date they can still use the app.

Is there a better way to do this ? or what are the alternatives

btw Thanks for your help Xav

[Xav]

Could you store the number of days left instead?

[reniery]

Yes I could, What kind of validation would I use to decrease the number of days left ?

[Xav]

What do you mean by validation?

[reniery]

Checking if something satisfies a certain criterion. I mean how would I know if its ok to decrease the number of days

[Xav]

Just run a simple "If" statement to check if the current value is bigger than 0. If so, decrease. If not... PAY TIME!

[DevilsCharm]

I didn't realize creating a license was so simple. Now all I need to do is learn how to write desirable programs.

[Xav]

Good one, DevilsCharm! :D

[TcM]

You are making all this too simple to crack.

A simple IF .. without any protection can be easily cracked using reverse engineering and making that IF a NOP (No Operation in ASM) and it will be easily skipped .. no one pays and everyone happy... except you.

[Xav]

Which algorithm would you suggest, then?