how can I put a time-limit on my software forcing the user to 'registrar it'

I wrote a great program and would like anyone who is interested download the program and use it for say 30 days, after which time, if they have a password, they can then use the software, and if they don't the program doesn't work. How can I implement this? Almost every program I download has this feature, so the code must be somewhere.

Any response anyone can give me will be greatly appreciated.

Hi,
Is that very difficult ?

I have seen programmers implementing this feature in several different ways. They are as follows:
1>When the user installs the package, write the current date into the registry.
Whenever the user runs your program , comapre the date with the one stored in the registry.

2>If you do not have any installation software for your program then check for the presence of a pre-defined registry key (HKLM\Software\..) every time your program is executed, if absent then create the key and print the date, if the registry key is present then comapare the date for validation.

3>If you do not like the registry business, then use initialization files instead.

Regards,
Saurabh

Those password programs are for the most part, *not* created "from scratch" by the author.

Usually a third-party package is used to put this type of "trial use" feature in the software. Programs such as TrialX, CrypKey, ShareLock are a few that come to mind. The people who create this type of software have way more exeperience in trying to stop hackers from breaking codes. Given that you claim that your program is great, It would be to your advantage to use one of these programs, and not try to do it yourself.

Having said this, even the most experienced hacker can break most protection schemes. You'll have to shop around and see which one will protect your program from the 90% to 95% of the public that won't try to crack the program.

Regards,

Paul McKenzie

I appreciate this question and the responses. I am curious though as to how anyone can crack a *.exe file. Does there exist an introductory guide to 'hacking' anywhere on the web?

A good response may significantly alter my view toward computer programming.

There are tools that can disassemble any EXE and can debug EXE's while running. Once the hacker inspects the code looking for the juicy parts that he/she needs to change, they edit the EXE file by replacing the original assembly language op-codes with their op-codes.

I remember back in the DOS days, some software included instructions on how to "patch" their programs by editing the EXE file using DEBUG. You would change the opcodes, and by doing this, you would patch a bug, add features, etc. If you get very old copies (at least 8 years old) of PC oriented magazines, you would routinely see articles on how to patch Lotus, WordStar, WordPerfect, etc. in this manner. The hacker is doing exactly the same thing, except he/she is breaking the protection.

Regards,

Paul McKenzie