Encrypt Your Data
Requiring a strong password to log onto accounts on your computer is a good security step. But when the government is your attacker, it's not nearly enough. If the government seizes your computer, all it has to do to get around your account protection is to take the hard drive out and stick it into another computer to get around your password protection. Similarly, if you were subject to a sneak-and-peek search, the government could sneak in with their own hardware, take your hard drive out and copy it, and then replace it without you ever knowing. Your best and only protection against this is to encrypt the data that's on your computer so the government can't read it !
Encryption is a technique that uses math to transform information in a way that makes it unreadable to anyone except those with special knowledge, usually referred to as a "key." There are many applications of encryption, but some of the most important uses help protect the security and privacy of files on your computer, information passing over the Internet, or left sitting in a file on someone else's computer. If encryption is used properly, the information should only be readable by you and people that receive the key from you. Encryption provides a very strong technical protection against many kinds of threats — and this protection is often easy to obtain.
How Does Encryption Work?
What do you need to know about how encryption works? Surprisingly little. Encryption is conceptually similar to the "secret codes" that children learn about and use to communicate. If you’ve ever spoken in pig Latin or used a decoder ring, you've used very simple encryption techniques on a message. Again, the idea is to take a normal human-readable message (often called the plaintext message) and transform it into an incomprehensible format that can only become comprehensible again to someone with secret knowledge:
Plaintext message + Encryption algorithm + Key = Scrambled message
Decryption algorithm + Key + Scrambled message = Plaintext Message
File and Disk Encryption
Theft or seizure threats can be mitigated by encrypting the data on the disk. Some sort of mitigation is especially important for laptops, which are at high risk of being lost or stolen, but the same measures can be useful for improving the security of any pc or workstation-type computer.
Full-disk encryption is meant to protect stored data against this sort of exposure, if the computer is stolen or seized when it is powered off. If the computer is seized while running, there are tricks that sophisticated adversaries could use to read the data regardless of encryption.
File encryption is disk encryption that only applies to certain specific files on your computer. It may be easier to deploy but is vulnerable to several threats that do not apply to full disk encryption.
Hard disk passwords are a feature offered by many laptop manufacturers. These can be enabled within the BIOS of your computer. Hard disk passwords don't encrypt any data on your drive, they just prevent the drive from cooperating with the computer until the password is supplied. There are numerous commercial services which will disable these passwords for about $100 per drive. So a hard disk password is useful against a casual thief, but of no use against law enforcement or other non-casual adversaries.
Disk Encryption Is Of Little Use in Civil Lawsuits
It is extremely important to note that disk encryption is unlikely to offer much protection against civil litigation. Many of the procedural obstacles which might apply to law enforcement attempts to obtain encrypted data during a criminal investigation would not apply in a civil case. If an adversary in a civil case persuades a judge to issue a subpoena for your data, a failure to decrypt and disclose the data would be held against you in the case.
If your threat model involves civil litigation, it is essential to simply not have the data on a computer in the first place, or to have secure deletion practices in place long before any lawsuit is filed. Once a lawsuit is filed, you will be obliged to preserve any pertinent documents, and the presence of forensic evidence that you deleted data after a suit was filed would have dire consequences.
Choosing Disk Encryption Software
There are many full-disk encryption tools. Using a mainstream one is probably safer than an obscure one, since mainstream disk encryption products have usually received more expert review. Leading disk encryption programs include DiskCryptor,BitLocker, PGPDisk, FileVault, TrueCrypt, and dm-crypt (LUKS); some of these come with the operating system, while others are third-party add-ons. You can read a detailed comparison of these and many other disk encryption products from a comparison at Wikipedia. This comparison may help you select a disk encryption product to meet your needs, but any of these systems can protect your data better than having no disk encryption at all.
Things To Know When Using Disk Encryption
Generally, disk encryption software will require you to enter a separate disk password when you turn the computer on or start using the disk (some systems can use a smartcard instead of or in addition to a password). To be effective, this password must be resistant to all forms of automated guessing. Remember that the disk encryption is fully effective at preventing access to the disk when the computer is turned off (or the encrypted disk is entirely unmounted or removed from use); to get the full benefit, you should unmount the encrypted disk or turn the computer off in any situation where the risk of compromise is especially high, such as a computer left unattended overnight or a laptop being carried from place to place. (Using disk encryption without following this precaution scrupulously will still provide more protection against some attackers than not using disk encryption.)
Finally, full-disk encryption can also be used on servers, providing some protection against seizure of the servers. However, even servers with encrypted hard drives could be vulnerable to attackers with specialized techniques if they're seized while they're operating. Proper use of disk encryption on servers can also be a nuisance because the server can't do a fully unattended automatic reboot. (It's not safe to store the password for the disk on the server itself, so an administrator will have to enter the disk password whenever the computer is restarted.)
One interesting property which some disk encryption developers are working towards is plausible deniability. The goal of these efforts is to offer users a way to not only encrypt their files, but to prevent an attacker from being able to even deduce the existence of some of the encrypted files. The user will have a way to "plausibly deny" that the files exist.
One example of this concept is DiskCryptor's ability to have an encrypted partition (which can be hidden as any file on your hard drive) and within that partition hide another partition. One password will reveal the outer partition and another separate password will reveal the inner one. Because of the way DiskCryptor encrypts the partition table itself, an observer cannot detect a hidden partition even if she has access to the "regular" encrypted share. The idea is to give the user something to decrypt if a law enforcement officer or Customs official asks, while keeping the rest of their information secure.
In practice, DiskCryptor's first attempt to implement this feature was shown to be ineffective because operating systems and applications leave so many traces of the files they work with, that a forensic investigator would have many avenues by which to determine that the inner partition existed. The DiskCryptor developers have responded to this research by offering a way to install and boot from an entire separate operating system within the inner partition. It is too soon to know whether their new approach will turn out to offer secure plausible deniability.
Technical issues aside, remember that lying to a federal law enforcement officer about material facts is a crime, so if a person chose to answer a question about whether there were additional encrypted partitions on a computer, they would be legally obligated to answer truthfully.
The following table is my personal recommendations when selecting a
| PARAMETER | RECOMMENDATION |
| block cipher | AES, Serpent |
| symmetric key size | at least 128bits |
| hash functions | SHA-2 (SHA-224, SHA-256, SHA-384, SHA-512)|
| | Whirlpool |
Cryptography for dummies:
- Ciphers: http://en.wikipedia.org/wiki/Cipher
- Block ciphers: http://en.wikipedia....ki/Block_cipher
- Block size: http://en.wikipedia...._(cryptography)
- AES: http://en.wikipedia....yption_Standard
- Serpent: http://en.wikipedia....erpent_(cipher)
- Hash function: http://en.wikipedia....i/Hash_function
- SHA: http://en.wikipedia...._hash_functions
- Whirlpool: http://en.wikipedia.org/wiki/WHIRLPOOL
- Passphrase: http://en.wikipedia....wiki/Passphrase
- Weak key: http://en.wikipedia.org/wiki/Weak_key
- LinuxCryptofs: http://wiki.boum.org...t/LinuxCryptoFS
Edited by jay pheno, 24 May 2010 - 07:57 AM.