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On Windows, I frequently use Eraser, to delete securely the files I remove.

I've been looking at TrueCrypt recently, and its whole disk encryption.

If I encrypt the whole disk, does that make using secure deletion tools moot? I mean, could someone still find what was deleted?

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7 Answers 7

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The deleted files still lurking in the filsystem (that Eraser would delete) will be encrypted as well, as the whole filesystem is encrypted. So it ends up with how secure one thinks it is to encrypt the disk with TrueCrypt. One can only find the deleted files if one can get access to the crypted filesystem (with password or cracking it).

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The only way to completely protect data is to destroy all copies of it beyond possibility of recovery. So yes...shred your disks. And if you've memorized any of the data, shred your brain too.

http://xkcd.com/538/

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  • Yessss, exactly :]
    – Kirill Strizhak
    Jul 29, 2009 at 14:18
  • Love the cartoon!
    – Michael Kohne
    Jul 29, 2009 at 14:31
  • Thanks for the laugh! That cartoon is hysterical but sooooo very true.
    – Axxmasterr
    Jul 29, 2009 at 15:52
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    While the cartoon makes a good point, it's worth noting that the truecrypt designers also thought of this: truecrypt.org/docs/?s=plausible-deniability
    – wcoenen
    Jul 30, 2009 at 0:37
  • Yeah, I love the hidden volumes feature.
    – sangretu
    Jul 30, 2009 at 12:24
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It depends. Using TrueCrypt definitely gives you better security. That's because if someone's looking for your deleted files then s/he have to get your TrueCrypt credentials. Then s/he can decrypt your file system and maybe can get back your deleted data.

Getting your password or the encryption key is not as hard as it seems to be. (Well, if the attacker gets physical access to your computer.) There are hardware and software keyloggers. There's the cold boot attack, just to name a few.

However, shredding your entire encrypted volume is extremely easy. All you have to do is to shred the encryption key. This is usually a few kilobytes. For example, if you want to "destruct" a TrueCrypt volume just shred the first megabyte of the volume and it's very unlikely that someone will ever get any data back from it.

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  • Thanks for that clear response, you were the runner-up for the accepted answer, joakim was faster :)
    – Manu
    Jul 29, 2009 at 18:56
  • I'm glad I could help you :)
    – KovBal
    Jul 29, 2009 at 19:47
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Well, just in case someone beats the password out of you... Or places small spy camera above your keyboard... Maybe it is reasonable.

It all depends on levels of data sensitivity and paranoia, I think.

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I will give you the answer from a security professional's perspective.

Hard disk encryption is indeed a good feature and it can keep all but the most savvy users out of your data, however something to note here is that is indeed possible to get in.

One method which has been making some news lately is to cryogenically cool the memory module so that it can be removed and inserted into another machine before the memory zeros out. This gives them access to everything in memory including the encryption key that keeps your data secure.

So the short answer is that file shredding is still needed if you do not want others to potentially have access to the data. Even a fully encrypted hard drive still can be broken by a person with the right skills. Just look at Bruce Schneier. He makes a living as a consultant training people how to protect from these kinds of threats. A cryptanalyst could certainly get in and gain access to the data should they have sufficient motivation and enough computer power to throw at the problem.

Another note on many of these encryption schemes. The only truly secure encryption method is a "One Time Pad"... Everything else generally has a mathematical solution which is how they know when they have cracked the code. A one time pad is not breakable with any amount of processing power because it is not a math problem but a problem of knowledge.

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    I find this answer to be somewhat misleading. The cryo method has been documented, but requires access to an up-and-running system. If a bad-guy has that, he doesn't need cryo to get your data. Also, even though "enough computer power" will allow someone to "certainly get in", there isn't enough computer power now to get in during the life of the universe.
    – bmb
    Jul 29, 2009 at 18:07
  • Actually, the cryo attack is relevant: It will e.g. allow you to get at a system that is running, but protected by a pw-protected screensaver.
    – sleske
    Mar 10, 2010 at 16:20
  • @BMB you obviously underestimate the worth of a good cryptanalyst. In several cases a cryptographic algorithm and the way it was implemented provide opportunities to significantly simplify the problem. The effort to crack SHA was reduced from the theoretical brute force required from 280 operations down to 269 operations. collisions in SHA-0 was achieved in 239 operations and collisions in 58-round SHA-1 in 233 operations. This is a significant economy of effort. Boiling away the ocean is not required anymore. A 42U rack of 1U terra stations is capable of 156 Teraflops.
    – Axxmasterr
    Mar 10, 2010 at 22:11
  • I still contend that the statement "a cryptanalyst could certainly get in" is somewhat misleading. Your specific example does not equate to certainty in my mind.
    – bmb
    Mar 10, 2010 at 23:52
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Encrypting does not negate the need for file shredding. There are ways to get around Truecrypt if someone gains physical access to your machine.

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    There are ways to get around shredding if someone gains physical access to your machine. I'll just delete shred and link it to donothing or copy instead.
    – Cylindric
    May 2, 2012 at 8:42
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If the whole volume is encrypted with TrueCrypt, you do not need to shred anything on the volume, period. Read the TrueCrypt documentation.

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