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Old 04-01-2009, 09:07 AM   #1
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Encryption and plausible deniability


I'm using Debian Linux and I have a few questions regarding encryption.

I want to create a truecrypt container for a user that is automatically mounted on login, and dismounted on the user's eventual disconnection. I think this is possible using PAM.

However, I want to know if I can create a hidden container within the truecrypt container and have one login password that mounts the outer-container to the user's home directory, and then another login password that mounts the hidden container to the home directory.

So if I'm ever forced to hand over the passphrase, I give the passphrase to the outer container and not the hiddden one.

I guess this means that linux would have to accept two passwords for a single user and then pass that information on to Truecrypt. Is this possible?

Does anyone have any ideas / suggestions ?

Old 04-01-2009, 09:15 AM   #2
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Couldn't you just have the user type the password. That way you just don't have the password.

You could also tell him to create an ' encrypted container' that he could mount when needed.

Just a thought.
Old 04-01-2009, 09:41 AM   #3
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Thanks for the response eco.

I could do it manually, ie have the user login and then mount an encrypted container via a shell.

I would prefer (if possible) to do it automatically though. I wanted the user to sign in via gdm which would then start an XFCE session using an encrypted home directory.
Old 04-01-2009, 10:17 AM   #4
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For those of you not familiar with TrueCrypt's hidden volume feature, you may want to read this.

lroy1978 - There is no automatic way to do this that would not give away that something else is in the encrypted file
Old 04-01-2009, 04:00 PM   #5
Registered: Aug 2006
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If you had two password for a login, would that be evident in your shadow/passwd file, thus destroying your plausible deniability?

Also if you looking of PD in the US Court system, you can use external keys on a USB or Smartcard et cetera. In the US court system, if you won't give up your password, then they can put you in jail until you do. However they can't force you to give up your key. Just make sure its well hidden.

Last edited by wsduvall; 04-02-2009 at 08:41 AM.
Old 04-02-2009, 01:48 PM   #6
Registered: Sep 2008
Distribution: Slackware & Ubuntu
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lroy1978 - Have you thought about TrueCrypt's hidden OS capability? This will seem more "automatic" as there will be a password when the machine is booting up. The OS that loads will depend on the password typed. You can read more on TrueCrypt's website here.


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