Research team finds disk encryption foils law enforcement efforts

[qualia]

(PhysOrg.com) -- A joint U.S./UK research team has found that common encryption techniques are so good that law enforcement, from local to highly resourceful federal agencies, are unable to get at data on a computer hard disk that could be used to prove the guilt of people using the computer to perpetuate crimes. In looking at the current technology, the team, as they describe in their paper published in Digital Investigation, find that if criminals use commonly available hard drive encryption software, law enforcement very often is unable find anything that can be used against them.

Contrary to what we all see in the movies and on television, cracking an encrypted drive is not a simple thing; in fact, it’s so difficult that if someone has encrypted their hard drive, there is apparently little law enforcement (or anyone else) can do read the data on the drive. Adding to the frustration, at least on the part of law enforcement, is the fact that they can’t force people to give up their passwords.

The authors of the report suggest there are some things law enforcement can do, but they all must happen prior to a drive being buttoned up by encryption.

Specifically, they say that law enforcement should stop turning computers off to bring them to another location for study, doing so only causes the need for a password to be entered to read the encrypted data. Also, in some cases, doing so causes the data to be automatically destroyed. Fortunately, there are some tools forensics experts can use to gather data if it sits untouched, such as copying everything in memory to a separate disk. The team also suggests that law enforcement look first to see if the drive has been encrypted before scanning it with their own software, as doing so will likely result in a lot of wasted time.

The unfortunate bottom line though, is that the authors openly admit that once the drive is encrypted, there is little to nothing to be done, which a lot of criminals are surely going to be really pleased to hear. The team suggests that the government embark on a research mission of its own to figure out a way to subvert encrypted drives or it will find itself with little reason to bother confiscating computers used by criminals to commit crimes in the future.

More information: The growing impact of full disk encryption on digital forensics, Digital Investigation, In Press. doi:10.1016/j.diin.2011.09.005

Abstract

The increasing use of full disk encryption (FDE) can significantly hamper digital investigations, potentially preventing access to all digital evidence in a case. The practice of shutting down an evidential computer is not an acceptable technique when dealing with FDE or even volume encryption because it may result in all data on the device being rendered inaccessible for forensic examination. To address this challenge, there is a pressing need for more effective on-scene capabilities to detect and preserve encryption prior to pulling the plug. In addition, to give digital investigators the best chance of obtaining decrypted data in the field, prosecutors need to prepare search warrants with FDE in mind. This paper describes how FDE has hampered past investigations, and how circumventing FDE has benefited certain cases. This paper goes on to provide guidance for gathering items at the crime scene that may be useful for accessing encrypted data, and for performing on-scene forensic acquisitions of live computer systems. These measures increase the chances of acquiring digital evidence in an unencrypted state or capturing an encryption key or passphrase. Some implications for drafting and executing search warrants to dealing with FDE are discussed.

http://www.physorg.com/news/2011-11-team-disk-encryption-foils-law.html

"if you have nothing to hide then what are you afraid of?"

[ThunderIdeal]

nothing to hide? how about half the ebooks that have been posted here.

torsten always says that refusing to give them your password is a crime. there are ways around this, perhaps, likewise there are ways into encrypted volumes or at least part of the data which has been written to ram. if you are concerned enough drink deeply of your encryption software's help section.

[tripsis]

Doesn't really seem to apply here. I recall Torsten saying on more than one occasion that not giving up encryption passwords to law enforcement can lead to 15 years in gaol.

Edit: beat me to it TI!

Edited November 22, 2011 by tripsis

[qualia]

15 years? huh.

what if you say you honestly forgot? i don't have passwords i have files i take a number of characters out of an md5 hash, sometimes i join characters for two if i'm afraid of people hacking it (like my router password)

[qualia]

of course if you go changing the file it completel screws everything up as i accidentally did the other day

[ThunderIdeal]

you can have a hidden volume in a fake outer volume. hand them the password to the fake volume.

[Sheather]

Hidden encryption drives can likely be found by looking at the hardware. A 600Gb harddrive with 500Gb of unhidden space is still suspicious. Better to have nothing on the HDD that is illegal. Perhaps something could be done with proxies and cloud storage? Encrypted files uploaded via 2 or 3 proxies (each of them in separate countries) could perhaps be safer.

[CβL]

What you want, gentleman and ladyfolk, is 'deniable encryption'. It's a little bit like what Thunderideal said:

Modern forms of deniable encryption

Modern deniable encryption techniques exploit the pseudorandom permutation properties of existing block ciphers, making it cryptographically infeasible to prove that the ciphertext is not random data generated by a cryptographically secure pseudorandom number generator. This is used in combination with some decoy data that the user would plausibly want to keep confidential that will be revealed to the attacker, claiming that this is all there is. This form of deniable encryption is sometimes referred to as steganography.

One example of deniable encryption is a cryptographic filesystem that employs a concept of abstract "layers", where each layer would be decrypted with a different encryption key. Additionally, special "chaff layers" are filled with random data in order to have plausible deniability of the existence of real layers and their encryption keys. The user will store decoy files on one or more layers while denying the existence of others, claiming that the rest of space is taken up by chaff layers. Physically, these types of filesystems are typically stored in a single directory consisting of equal-length files with filenames that are either randomized (in case they belong to chaff layers), or cryptographic hashes of strings identifying the blocks. The timestamps of these files are always randomized. Examples of this approach include Rubberhose filesystem and PhoneBookFS.

Another approach utilized by some conventional disk encryption software suites is creating a second encrypted volume within a container volume. The container volume is first formatted by filling it with encrypted random data,[3] and then initializing a filesystem on it. The user then fills some of the filesystem with legitimate, but plausible-looking decoy files that the user would seem to have an incentive to hide. Next, a new encrypted volume (the hidden volume) is allocated within the free space of the container filesystem which will be used for data the user actually wants to hide. Since an adversary cannot differentiate between encrypted data and the random data used to initialize the outer volume, this inner volume is now undetectable. Concerns have, however, been raised for the level of plausible deniability in hiding information this way – the contents of the "outer" container filesystem (in particular the access or modification timestamps on the data stored) could raise suspicions as a result of being frozen in its initial state to prevent the user from corrupting the hidden volume. This problem can be eliminated by instructing the system not to protect the hidden volume, although this could result in lost data. FreeOTFE[4] and BestCrypt can have many hidden volumes in a container; TrueCrypt is limited to one hidden volume.[5]

http://en.wikipedia.org/wiki/Deniable_encryption