Take a look at NetLib® Encryptionizer™ Desktop Edition
http://www.netlib.com/soft1.htm

>>I wrote my own protection routines to limit the number of runs and usage time. Basically each time the software is launched it writes to the registry. Re-installion won't help since the values are still in the registry. Uninstall programs won't break protection because registry-writing is not part of the installation procedure. Both the number of runs and installation date are recorded in a non-obvious format. I also record these in a local table and compare them to registry values to detect things like backdating. For an added security measure, I also check then number of records in a key table to make sure they are under a certain max.
>>
>>As for encryption, you can do some search and you'll find a lot of algorithms out there. I suspect you're only trying to keep users from breaking the demo so a simple algorithm should suffice.
>>
>>Mon
>>
>>>?? could anyone recommend a utility or method for controlling
>>> any or all of these aspects of demo software use:
>>>
>>>1) limiting the # times or length of time it can be used
>>>2) encrypting or obscuring data structures
>>>3) encrypting or hiding readable code
>>>4) preventing unlimited re-installs.
>>>
>>>would be very interested in suggestions.
>>>
>>>thanks
>
>
>thanks mon,
>received helpful replies from other, advising on products to
>do these things, but i like your approach, as it is straightforward
>and you know exactly what it is implemented.
>
>additionally,
>i wish i could think of a way to hide table structures and content too.
>i have one app where those are AS (or more) important that the program
>itself. for example, i've take a lot of time to develop a encoding
>scheme for certain medical data. the actual end-users don't know how to
>pirate that info (other than hand copying it from the tree-list
>controls in which it is displayed) ... but they could easily find somebody
>to do it for them. i suppose i could encrypt the fields and decrypt
>them as i read them in, but that would slow everything down.
>????