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Is it kind of impossible to decrypt data that is encrypted by BitLocker and data will be safe enough if my computer was stolen?

  • Opinion: I wouldn't rely on just BitLocker if people's lives depended on it. I would depend on it for most "normal" use. – Julian Knight Dec 15 '16 at 19:52
  • what else you recommend? – Hany Pharmacy Dec 15 '16 at 21:46
  • You would need to give more info. Depends on the information. Personally I use a mix of TrueCrypt (actually VeraCrypt) containers and KeePass (with some attachments) along with Bitlocker. Defense in depth is the key. But then I don't have life & death data to handle, I'm just careful. – Julian Knight Dec 15 '16 at 23:30
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In theory as long as you keep the encryption key separate from your device and it is not stolen also you should be fine. However not so long ago a security researcher found a way to bypass bitlocker altogether on domain joined devices. The biggest problem with encryption is not the algorithms but the implementation. Since Bitlocker isn't open source it has never been audited by the community so we can't know if there are more "accidental" backdoors. You could say that bitlocker is good enough and if someone does steal your device it's probably not going to be the NSA. I'd rather go with open source solutions that have been verified by the community such as veracypt (the replacement of truecrypt) for instance. Here is a very good read on the whole topic.

  • I think the "open source can be audited so its more secure" thing doesn't hold up in practice. Major errors like Heartbleed and Shellshock have shown that while it's possible for open source to be reviewed, nobody actually bothers to do it. Microsoft has the $$$ to pay for frequent security reviews, pen tests, etc. Of course backdoors are a separate issue, and it's obviously easier to hide a backdoor in closed source software, but again unless anyone is actually combing over every line of an open source project, it's no more secure than closed source. – Robert Fraser Dec 15 '16 at 5:05
  • The other difference is that if people do find issues in an open source project, they're more likely to report them and get them fixed, rather than sell the flaw to the highest bidder. Getting enough suitably skilled people to look at open source code is a problem though. – Matthew Dec 15 '16 at 15:49
  • And it is perfectly possible to pay someone to test your application for vulnerabilities. So the real issue is the level of trust. This is why we have government (and other) certifications for various aspects of security. That is what to look for in order to understand the level of trust you can have in any application. – Julian Knight Dec 15 '16 at 19:49
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Igor Liv's answer elsewhere on this page addresses BitLocker specifically. My answer will instead address BitLocker simply as an example of full disk encryption (FDE). In other words, my points below should be applicable to other conventional FDE software packages, such as TrueCrypt.

Is it kind of impossible to decrypt data that is encrypted by BitLocker?

No, it is not impossible. Anyone who has the decryption key should able to decrypt data encrypted by BitLocker. BitLocker would not be useful otherwise.

Additionally, there is a risk that BitLocker's design or implementation has a weakness: either an intentional weakness ("backdoor") or an unintentional weakness (bug). Such weaknesses broadly divide into two categories: shortcomings in the implementation of the cryptographic algorithms themselves, or the presence of side-channels. (Here is a discussion of one potential side channel, relating to SSD wear-levelling.) Opening the source code for the software, and having that code audited by trusted professionals, reduces the risk of such a weakness; but it is hard to eliminate such a weakness altogether, short of formally verifying the software.

and data will be safe enough if my computer was stolen?

That depends upon a number of factors.

If your computer is stolen while it is switched on and you are logged in (e.g. if someone snatches your laptop from you at a cafe while you are working on it), then as long as the thief can keep the laptop awake, BitLocker will not prevent them from viewing your files.

Alternatively, if an attacker obtains a copy of your decryption key, then the attacker will be able to access your data. That might occur if your key (or the passphrase used to protect your key) is weak and susceptible to a brute-force attack, or if your attacker uses some other means to obtain your decryption key, such as a DMA attack, a cold boot attack or an evil maid attack. See Daniel Selifonov's DEF CON 21 talk A Password Is Not Enough: Why disk encryption is broken and how we might fix it for a longer discussion of attack vectors like this, and potential mitigations.

Finally, if BitLocker's design or implementation has a weakness (see above), then an attacker may be able to access your data.

  • Don't forget potential issues with SSD's as well, any FDE application has to have a way of dealing with the "leveling" issue. – Julian Knight Dec 15 '16 at 19:51
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    @JulianKnight, fair point. Edited accordingly. – sampablokuper Dec 16 '16 at 13:28

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