On Sat, 2010-05-15 at 11:50 +0100, Lester Caine wrote:

> This was bounced back to the list because of the php crap of needing to use 
> 'reply all' - I SHOULD have used 'reply' in this case as jagdeep's email was 
> to 
> ME, but I automatically 'reply all' and replace return address with the list 
> email to kill off all the extras!
> Ashley Sheridan wrote:
> > On Sat, 2010-05-15 at 08:18 +0100, Lester Caine wrote:
> >> Jagdeep Singh wrote:
> >> >  How can I define"Machine"?
> >>
> >> That IS the problem. As with a lot of this stuff - nothing was ever 
> >> actually
> >> DESIGNED to work :( So $_SERVER["REMOTE_ADDR"] will block multiple 
> >> machines if
> >> they are sharing the one connection. I've been lucky so far in that
> >> 'REMOTE_ADDR' CAN be resolved to a machine in my own case.
> >>
> >> This like 'tzoffset' is an area where the simplest basic functions 
> >> actually need
> >> to be fixed. If you are working cross timezones have you considered the 
> >> problem
> >> of knowing the right time where daylight saving is important. My users 
> >> have to
> >> set their correct daylight saving zone in their profile. 'tzoffset' is no 
> >> use.
> >>
> >> Both of these are areas that need fixing?
> >>
> >> ( As an aside ... some schools are now using 'virtual' desktops, so several
> >> pupils may WELL be working on the one 'virtual server' but each in their 
> >> own
> >> sessions. This makes it impossible to identify the individual users as 
> >> well )
> > I explained off-list how you could do this. Create a hash of the
> > machines IP and browser with the username of the logged in user:
> >
> > md5($ip . $browser . $username);
> >
> > And store that in the database when they log in. Now each time they
> > perform an action, create a hash from those same bits of information
> > again and check it against the one created when they logged in.
> We have already identified that THIS will not work is this case. It is not 
> unreasonable to want to restrict the number of users on a single machine. So 
> you 
> keep the machine use separate to the user login ... AS STATED the problem is 
> identifying a machine in the first place.
> > You can't access their Mac address. Many people on the list have
> > explained that to you now. I'm not sure why an e-learning module needs
> > such strict requirements, as it's perfectly valid that a user might want
> > to use more than one browser at a time.
> It is also not unreasonable that one may want to restrict access to something 
> in 
> the way specified. If one is RUNNING on-line testing, then having the answers 
> open in another browser is something that it might be nice to block ;) 
> Because 
> the simple matter of uniquely identifying a machine on the internet IS 
> impossible currently then we have to come up with some other way of blocking 
> things, but to be honest. On-line testing is a silly idea anyway since there 
> are 
> many ways of cheating that even these locks would not prevent ;) In my own 
> case, 
> restricting a machine to a single user is essential and I simply need to 
> block 
> other users when the machine is 'in use'. $_SERVER["REMOTE_ADDR"] is internal 
> to 
> the intranet so no problem.
> Personally I think the demands from the 'privacy' camp is simply playing into 
> the hands of the criminals. EVERY machine should report it's ID and this can 
> then be used to kill off the con men. Perhaps when IPv6 is in full use then 
> every computer can be uniquely identified? THEN $_SERVER["REMOTE_ADDR"] will 
> work properly .... we just have to ensure that 'cloaning' of ID's is always 
> flagged in transit.
> -- 
> Lester Caine - G8HFL
> -----------------------------
> Contact - http://lsces.co.uk/wiki/?page=contact
> L.S.Caine Electronic Services - http://lsces.co.uk
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> Model Engineers Digital Workshop - http://medw.co.uk//
> Firebird - http://www.firebirdsql.org/index.php

I see exactly the issue you have now, and there's no way round it. You
can't identify a single machine in the way you want.

Maybe you could restrict access to test answer materials to a user who
is logged in, and then lock them out when a test is in progress for
their username. That way, you don't have to identify a machine at all
(what's to stop someone from opening up a laptop next to their main
computer to circumvent your 'security' anyway?) and the only way they
can access both course materials and the test is with two sets of login


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