Re: Get time difference without time()
On 15 Mar 2001, at 5:40, Ted Fines wrote:
> >> Let me guess, You are wanting to do this to prevent the
> >> following scenario:
> >>
> >> Joe Blow downloads your shareware (time-limited) software.
> >> Joe Blow sets his computer clock to 5 years ahead.
> >> Joe Blow installs your software.
> >> Joe Blow sets his computer clock back to normal time...
> >> ... thus defeating your time-limit.
>
> As long as we're talking about this...Here's a solution:
> You have a company, supersoftware.com. On your server, you run an NTP
> server, tick.supersoftware.com. Your time-bombed software could compare
> the current date, as reported by your NTP server, to the installed date,
> and act accordingly.
> Problems:
> 1) User has to have Internet connection to use software
> 2) Sophisticated user could setup their own local NTP server, and spoof
> yours.
>
> The fix for #2 is to access the server using SSL with a Verisign-signed
> certificate. I don't know if NTP can actually be tunneled through this, so
> you might just have to have your program access a secure HTTP server, the
> URL of which simply shows the current date & time. I don't see how this
> could be spoofed...
>
> I don't have a fix for #1. You'd just have to tell users that they'd have
> to be connected...
>
> Didn't say it was practical (though it seems pretty practical if you're
> talking about millions of dollars in revenue :) ), didn't say you'd want to
> do it. But it seems pretty simple, and workable, really. I guess whether
> #1 is a problem depends on the type of software, and client expectations...
Have the server that sent the software hard code the current date and the crash
date
into the software in an encoded form, before sending it. Then have the software
check
the system date on the puter, and calculate the time till crash and/or running
time.
Sooner or later, the crash date will be hit and the software will erase itself.
Kat
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