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Home » Developing U++ » External resources » Timed demos
Timed demos [message #28248] Wed, 25 August 2010 09:20 Go to next message
mdelfede is currently offline  mdelfede
Messages: 1307
Registered: September 2007
Ultimate Contributor
Hi,

I need to deploy a demo of my app with a time limit.
There's an easy (and portable) way to check for it and, of course, to check if user puts it clock back ? Smile

Ciao

Max
Re: Timed demos [message #28256 is a reply to message #28248] Wed, 25 August 2010 11:12 Go to previous messageGo to next message
koldo is currently offline  koldo
Messages: 3355
Registered: August 2008
Senior Veteran
Hello Massimo

The simple way I use is to have an encrypted configuration file (a .xml file from Xmlize coded with AESStream) with install date/time and last use date/time.

If the program is opened after passing license date or before last use date ( Twisted Evil ), it will ask for a new license.


Best regards
Iñaki
Re: Timed demos [message #28264 is a reply to message #28256] Wed, 25 August 2010 12:44 Go to previous messageGo to next message
mdelfede is currently offline  mdelfede
Messages: 1307
Registered: September 2007
Ultimate Contributor
koldo wrote on Wed, 25 August 2010 11:12

Hello Massimo

The simple way I use is to have an encrypted configuration file (a .xml file from Xmlize coded with AESStream) with install date/time and last use date/time.

If the program is opened after passing license date or before last use date ( Twisted Evil ), it will ask for a new license.


Mhhhhh.... and what if user erases the config file and starts again with a fresh one ?

I mean.... I can't encrypt data files, they're xml on purpose, user should be able to look/correct/recover them.
The config files could be encrypted, but then user can erase them with no problem....

Max

[Updated on: Wed, 25 August 2010 12:46]

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Re: Timed demos [message #28266 is a reply to message #28264] Wed, 25 August 2010 13:26 Go to previous messageGo to next message
tojocky is currently offline  tojocky
Messages: 607
Registered: April 2008
Location: UK
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mdelfede wrote on Wed, 25 August 2010 13:44

koldo wrote on Wed, 25 August 2010 11:12

Hello Massimo

The simple way I use is to have an encrypted configuration file (a .xml file from Xmlize coded with AESStream) with install date/time and last use date/time.

If the program is opened after passing license date or before last use date ( Twisted Evil ), it will ask for a new license.


Mhhhhh.... and what if user erases the config file and starts again with a fresh one ?

I mean.... I can't encrypt data files, they're xml on purpose, user should be able to look/correct/recover them.
The config files could be encrypted, but then user can erase them with no problem....

Max



You can provide the config file with the program. initial the file will contain a start evaluation date and an unique ID for verification.
Re: Timed demos [message #28270 is a reply to message #28266] Wed, 25 August 2010 14:06 Go to previous messageGo to next message
mdelfede is currently offline  mdelfede
Messages: 1307
Registered: September 2007
Ultimate Contributor
Mhhhhh.... nope, again.
If the user erases the config file, put timer back and redo the config file from the original one, it's ok for him.
Yep, quite uncomfortable, but would defeat the purpose.

The only cheap way I see is to put in data files a small encrypted part containing last saving date and CRC of whole datafile.
BUT, then the user could not recover or modify by hand the datafile, ever, ad that's not what I need.

I think that what we need is a way to detect the changing of PC time in a reliable and portable way.

Thinking about it.... a partial solution would be to insert an encrypted date in datafiles, with CRC *ONLY* on it.
So user could edit the data by hand, but not touch at the encrypted part.... But again, if he's smart enough he could copy just the encrypted part and insert it on other files.

No more hints ? Rolling Eyes

Max


Edit : I should explain better what I want do to :

1) Put the app free to download, but limited in funcionality.
Just compiled with some missing part, impossible to crack, of course.

2) Offer the app for a monthy trial to registered users; the app gets username and expiring date hard-coded.
It's crackable, but limited to registered users.

3) Send the full-functional app without any protecton, just the user's data hard-coded on it, upon purchase.
I don't want to limit user to run it on many computers nor to have some dongle around.... Just want that who pay can use it and copy it, just have it's name on all printouts.

So, points 1 and 3 are easy, I just need a reliable way for point 2.

Max

[Updated on: Wed, 25 August 2010 14:10]

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Re: Timed demos [message #28277 is a reply to message #28270] Wed, 25 August 2010 14:44 Go to previous messageGo to next message
koldo is currently offline  koldo
Messages: 3355
Registered: August 2008
Senior Veteran
Hello Massimo

I understand you. An imperfect way to solve this would be to include a encrypted file with install date and last run end somewhere hidden in the computer. With this the user would have to be careful to set the computer time a second after last run end Smile.


Best regards
Iñaki
Re: Timed demos [message #28278 is a reply to message #28277] Wed, 25 August 2010 15:12 Go to previous messageGo to next message
mdelfede is currently offline  mdelfede
Messages: 1307
Registered: September 2007
Ultimate Contributor
koldo wrote on Wed, 25 August 2010 14:44

Hello Massimo

I understand you. An imperfect way to solve this would be to include a encrypted file with install date and last run end somewhere hidden in the computer. With this the user would have to be careful to set the computer time a second after last run end Smile.


Eh... by experience, an hidden file is the easiest stuff to find Smile
For windows there's the registry, you can hide quite many things there, but for linux ?

Mhhhh... maybe I've got a nicer idea, which could be combined with the rest.
Access to a time server could do the job. It could be triggered randomly, and accept some failures, if the user isn't connected to the net.

Max
Re: Timed demos [message #29696 is a reply to message #28278] Mon, 08 November 2010 22:45 Go to previous message
nlneilson is currently offline  nlneilson
Messages: 644
Registered: January 2010
Location: U.S. California. Mojave &...
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Hi Max

What did you end up using?

I use just a time limit for the trial, that works OK without problems.

My thoughts, intent:
Registering the commercial apps (several small ones) to the computer ID. If there is a time limit just don't worry about it. For a user for a few $$ it would be easier and more cost effective than changing the computer time.

Neil

[Updated on: Mon, 08 November 2010 22:47]

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