.  One last note: if you store a Truecrypt volume in the "cloud", it's already compromised: you can compare differences between versions and derive the keys that way, since the data is being intercepted bit-by-bit at the ISP itself..  One last note: if you store a Truecrypt volume in the "cloud", it's already compromised: you can compare differences between versions and derive the keys that way, since the data is being intercepted bit-by-bit at the ISP itself..  One last note: if you store a Truecrypt volume in the "cloud", it's already compromised: you can compare differences between versions and derive the keys that way, since the data is being intercepted bit-by-bit at the ISP itself..  However it is quite an extrapolation to think that the hibernate file is somehow then passed across the internet.  Then again, if the FBI can get into Google I don't see why they can't get into wherever your truecrypt cloud provider is to access the memory and do decryption. Of course they would obviously need a serious reason to go to these lengths.  One last note: if you store a Truecrypt volume in the "cloud", it's already compromised: you can compare differences between versions and derive the keys that way, since the data is being intercepted bit-by-bit at the ISP itself.  If that were the case, Truecrypt would already be worthless, because someone could image your drive, let you work on it, make another image, and compare the two.  Luckily, thats not how encryption works, and the attack you describe cant be generalized without knowing a lot more about how things are encrypted. You appear to be describing a "Known-Plaintext attack", which Wikipedia notes modern encryption schemes (such as AES) are not vulnerable to.http://en.wikipedia.org/wiki/Known-plaintext_attack  Truecrypt is only "vulnerable" if you use crappy keys, or a crappy encryption algorithm (DES or something), or if you get keylogged.  