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I have some Truecrypt volumes stored on my USB drive and I would like to know if they are safe from being cracked by the FBI or any government agencies? Some people say Full Disk Encryption will prevent the FBI from snooping through your files but I would like to know if Truecrypt volumes are just as safe and can provide enough protection from your files being accessed. I know about dictionary attacks, bruteforce attacks, and cold boot attacks. But with a strong password be enough for the FBI not to get into my files? Also, how do I prevent a cold boot attack on a Truecrypt flash drive volume? Some say making a volume itself is not safe and government agencies will still access your files and you should use full disk encryption instead, but I wanna know if that is the case or not. Thanks.

closed as primarily opinion-based by TildalWave, Xander, Adi, Steve, AJ Henderson Mar 31 '14 at 14:08

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    So what do you want to hide from us? - The NSA – Lucas Kauffman Mar 30 '14 at 15:34
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Also, how do I prevent a cold boot attack on a Truecrypt flash drive volume?

You don't. The sensitive areas are sanitized if the system is shut down properly, while any cleartext data will still be available and decay exponentially with time. So either make sure that no one will access your system for a few minutes after a shutdown, or re-boot again from a CD using MemTest to perform a R/W test of the whole DRAM. That will completely erase any traces from dynamic memory.

Regarding MemTest and similar tools, you want to perform the fastest test that will overwrite the whole memory. Thoroughly testing 1000 times each kilobyte might result in a 30-seconds test, which, if interrupted at once, will only have overwritten maybe the first 200M of RAM, leaving the rest intact. Testing once the whole RAM will overwrite everything in 30 milliseconds, and with RAM, a single overwrite is enough.

A good UPS can prevent unexpected shutdowns and reinstate the possibility of booting a cleanup CD.

There are also kits to extend the boot sequence. A write-and-check routine could pass for a reasonable precaution against hardware faults, and be a very good countermeasure against coldboot attacks (provided it's not known beforehand). You can make it so, unless you boot with both SHIFT keys pressed, the boot is slightly slowed down - we're talking a couple of seconds here - by a complete DRAM overwrite. Or you can always have an overwrite performed, just in case, without displaying anything.

This will still not protect against an attacker dumping the computer in liquid nitrogen, removing the RAM and mounting them in a different harness.

As for data security, volumes or whole disks are really similar for all practical purposes in your scenario, unless you go to great lengths to ensure "plausible deniability" (i.e. maintain an outer disk with a credible history, which is actually a lot of work). A can of strong acid and an external disk that will fit inside without sploshing might be a better solution.

However, lacking other information, this looks like a webcomic situation.

Try first determining your actual threat model. If men in black may really seize your disks, then chances are that they are able and willing to seize you. In that case, what you really should want is a password that's easy to remember (so you don't accidentally tell a wrong one to the nice guy with the helpful smile), or start thinking along the lines of "cyanide pill".

("Plausible deniability" using two passwords is only okay if you invest an inordinate amount of time in maintaining the deniable maskirovka, and actually the deniable partition is your main drive).

Strong encryption in your scenario looks like either too much, too soon, or too little, too late.

  • I would actually advise against using MemTest or variations. When the system is immediately rebooted, the RAM is powered up again and anything not lost is refreshed and will continue to exist until MemTest finally wipes those addresses. It's very possible that simply letting the system stay off will result in memory being wiped faster than if you immediately reboot into MemTest. – forest Sep 14 '18 at 2:01
  • @forest good point. Amending answer. – LSerni Sep 14 '18 at 10:47
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  • Non technically, it really depends on what country you live in. A three letter agency might not be able to crack the encryption, but they might be able to legally force you to give them the key. In United States, recent precedent seems to say that if the authorities have a reasonable idea of WHAT is encrypted, they can force you to give them the key. If they do not have a reasonable idea of what is encrypted, then they are "fishing" and you can't be forced to incriminate yourself. Again depending on the country and the vigilance of the citizenry, they could also extra-legally force you to give them the key via torture. Both of these methods are variations of the rubber-hose attack and it works against most encryption. Experts suggest that the protection against these this non-technical vulnerability is to hide the fact that there is encryption in the first place. For example, have an encrypted volume that contains another, hidden encrypted volume. You will gladly hand over the key to the outside volume and pray that the inner, hidden one is not found.
  • From a purely technical perspective, TrueCrypt has been considered safe but there is an ongoing comprehensive audit of TrueCrypt to see how safe it really is. I haven't seen any findings that there is a way to break either whole disk encryption or encryption of a USB. That is, the encryption can not be broken. Clever attackers, when confronted with unbreakable encryption will go around it. You should read up on ways to capture the encryption key in memory as truecrypt will generally keep the key in memory for fast access to the encrypted volume. If the system is captured in this state, then the key can be captured. Also, if the system is compromised, the keystrokes used to enter the encryption key can be captured.

So, the short answer is that the encryption part of TrueCrypt is currently considered solid but your question of "can the government read your USB" is subject to the above. TrueCrypt has also considered these things and has features such as Hidden Volume and Hidden Operating System.

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There are plenty of ways to get in besides the ones you mentioned (dictionary attacks, brute-force attacks, and cold boot attacks). Since the NSA has been reported to keep hidden security exploits to themselves, they probably have ways to get into even a fully-patched operating system and software running in it. You post implies a situation where the NSA, FBI, or ZYX have physical access to the Truecrypt volumes stored on your USB drive. In that case, by law #3 the 10 immutable laws of Security, your data is compromised. In fact, it might be easier for them to install malware on the computer while it's running (remotely) or while it's off (physically) than to take the USB drives from you. You can read about the laws here on Meta: https://security.meta.stackexchange.com/a/988/42975.

10 Immutable Laws of Security

Law #3: If a bad guy has unrestricted physical access to your computer, it's not your computer anymore

Your data storage devices are very much a part of your computer as it's not useable without one anyway.

  • +1 for physical access. Even if you lock up your computer or cover the motherboard with epoxy to prevent tampering something as simple as a hidden camera could still capture your keystrokes. – user2675345 Mar 31 '14 at 12:36
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But with a strong password be enough for the FBI not to get into my files?

That is correct. A brute force is impossible due to the immense key space. Look at the math if you'd like to verify this https://crypto.stackexchange.com/questions/6390/aes-key-ciphertext-space-sizes

While AES is technically broken (there is a faster method to getting the key than a brute force attack) it would still take trillions of years. http://www.theregister.co.uk/2011/08/19/aes_crypto_attack/

Also, how do I prevent a cold boot attack on a Truecrypt flash drive volume?

One method of cold booting it to plug in a USB drive with a live system on it and quickly reboot into that. The first thing is to lock down your bios with a password and only allow booting from devices you trust.

The second method of cold booting is to freeze the RAM chips which can make the contents last for several minutes and then swap them out into a computer the attacker controls.

To defend against this make it difficult to access the RAM in the first place. Consider putting a padlock on your computer case for example.

The third threat is if you need to leave in a hurry. Even if you shutdown the machine someone can boot it back up quickly. The first two defenses will work against this too but additionally there is the option of clearing ram on shutdown.

If your intention is to hide from the state, make sure you understand how key disclosure laws can affect you where you live. This is basically the reason Truecrypt hidden volumes were created. http://en.wikipedia.org/wiki/Key_disclosure_law

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