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I recently installed Guest Additions in my Windows 7 Virtual Machine because I could not stand working without widescreen and high resolution.
I have read somewhere that this could be a possible vulnerability that an attacker could use to enter the host system but I guess this risk I will take.

I am wondering if I imported my sensitive password safe files into my host system and later overwrite them using Eraser ( >30 Gutmann Passes) what a data forensic could do with the information he finds on my hard drive.

I think he would see that there are some segments on the hard drive that have been overwritten. I have a second cloud account containing a keepassfile with non sensitive data prepared to feed to those people in that case.

One problem I see is that the size of my keepassfile that I keep on a second cloud account containing non sensitive data is smaller than my sensitive keepassfiles. Furthermore my sensitive keepassfiles consist more than one file (I could change that of course by compressing them to a zip file or build one keepassfile out of the three).

I don't know if it would be better for me to continue like I do at the moment which means downloading my keepassfiles from a cloud server inside my virtual machine or if I should change my routine to downloading the files from the cloud server into my host system and use the shared clipboard function of Virtual Box to import each password string into the guest machine. Security-wise, I came to the conclusion that it would be better to copy and paste the files from the host machine into the virtual machine using a shared clipboard because if a homepage I visit exploits any browser vulnerabilities I would maybe get an alert from my antivirus and could roll the machine back to an earlier state without getting my keepasfiles lying on my host system infected/stolen.

The only problem I see is the plausible deniability factor.

If an adversary with data forensic skills would gain physical access to my machine and finds traces of the files I wiped after a session which differ in size from my "fake files" lying on my second cloud account he could start asking questions.

What I did for some time was reading the password in one virtual machine and typing it in into the virtual machine that I use for browsing but after a while it gets extremely annoying.

What are your thoughts regarding the improvement of security of my setup, and the plausible deniability and security of my keepassfiles?

Regarding the fact that I posted it anonymously I am not too concerned about the fact I did and also the fact that there are billions of people having the need for hiding their files for a lot of different reasons. I just want to know if sizewise the files must be the same if I wipe them with eraser. I am not talking about an NSA kind of threat model because they would maybe just enter my apartment when I am away, put cams and microphones everywhere and just watch me.

I need deniability because the secret keepassfile contains data I don't want anybody to know about. So in case somebody with data forensic skills would ask me I can show him another file that also contains maybe sensitive data but not too sensitive and that guy is fed and happy.

  • Except that you announced to the world that you have those files by posting on this site? :) – schroeder Aug 21 '14 at 1:24
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    why do you need deniability for a password file? – schroeder Aug 21 '14 at 1:25
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    I have tried to make your question readable, and incorporate the additional information you gave in comments. Hopefully the highlighted line is the question you meant to ask. Personally, I can't imagine that your threat model requires anything like this degree of complexity. – Rory Alsop Aug 21 '14 at 14:22
  • @schroeder - in some jurisdictions (notably the UK), you can be required by law to hand over a password if you have it, however it must first be proven that you posses it - thus the need for deniability. This is a public question, it can benefit others, not just the OP, who is now arguably being watched. – user2813274 Aug 21 '14 at 14:57
  • So, this boils down to a question of how to pass off a 2nd file as the original and how to maintain the 2nd file as the original changes? – schroeder Aug 21 '14 at 18:02
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I think you need to decide what your threat model is: things like who your opponent is, what capabilities they've got, what information you need to keep secret, and so on. It sounds like you're applying security-related techniques you've heard of without understanding what those techniques do or why you should (or shouldn't) use them.

The precautions needed for dealing with a "nosy little brother" threat are different from those for a "foreign intelligence agency" threat. In the first case, simply keeping your secret information hidden is good enough; in the latter, you need to keep the fact that you have a secret hidden, so they won't be tempted to beat it out of you.

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