Page 44 of 53
This is impressive:
With Winlockpwn, the attacker connects a Linux machine to the Firewire port on the victim’s machine. The attacker then gets full read-and-write memory access and the tool deactivates Windows’s password protection that resides in local memory. Then he or she has carte blanche to steal passwords or drop rootkits and keyloggers onto the machine.
Full disk encryption seems like the only defense here.
There’s a new version of TrueCrypt, the free open-source disk encryption software.
They advertise 128-bit AES encryption, but they use XOR.
This is why evaluating security products is hard: the devil is in the details.
There have been a lot of articles about the new attack against the GSM cell phone encryption algorithm, A5/1. In some ways, this isn’t real news; we’ve seen A5/1 cryptanalysis papers as far back as ten years ago.
What’s new about this attack is: 1) it’s completely passive, 2) its total hardware cost is around $1,000, and 3) the total time to break the key is about 30 minutes. That’s impressive.
The cryptanalysis of A5/1 demonstrates an important cryptographic maxim: attacks always get better; they never get worse. This is why we tend to abandon algorithms at the first sign of weakness; we know that with time, the weaknesses will be exploited more effectively to yield better and faster attacks.
Nice piece of research:
We show that disk encryption, the standard approach to protecting sensitive data on laptops, can be defeated by relatively simple methods. We demonstrate our methods by using them to defeat three popular disk encryption products: BitLocker, which comes with Windows Vista; FileVault, which comes with MacOS X; and dm-crypt, which is used with Linux.
[…]
The root of the problem lies in an unexpected property of today’s DRAM memories. DRAMs are the main memory chips used to store data while the system is running. Virtually everybody, including experts, will tell you that DRAM contents are lost when you turn off the power. But this isn’t so. Our research shows that data in DRAM actually fades out gradually over a period of seconds to minutes, enabling an attacker to read the full contents of memory by cutting power and then rebooting into a malicious operating system.
Interestingly, if you cool the DRAM chips, for example by spraying inverted cans of “canned air” dusting spray on them, the chips will retain their contents for much longer. At these temperatures (around -50 °C) you can remove the chips from the computer and let them sit on the table for ten minutes or more, without appreciable loss of data. Cool the chips in liquid nitrogen (-196 °C) and they hold their state for hours at least, without any power. Just put the chips back into a machine and you can read out their contents.
This is deadly for disk encryption products because they rely on keeping master decryption keys in DRAM. This was thought to be safe because the operating system would keep any malicious programs from accessing the keys in memory, and there was no way to get rid of the operating system without cutting power to the machine, which “everybody knew” would cause the keys to be erased.
Our results show that an attacker can cut power to the computer, then power it back up and boot a malicious operating system (from, say, a thumb drive) that copies the contents of memory. Having done that, the attacker can search through the captured memory contents, find any crypto keys that might be there, and use them to start decrypting hard disk contents. We show very effective methods for finding and extracting keys from memory, even if the contents of memory have faded somewhat (i.e., even if some bits of memory were flipped during the power-off interval). If the attacker is worried that memory will fade too quickly, he can chill the DRAM chips before cutting power.
There seems to be no easy fix for these problems. Fundamentally, disk encryption programs now have nowhere safe to store their keys. Today’s Trusted Computing hardware does not seem to help; for example, we can defeat BitLocker despite its use of a Trusted Platform Module.
The paper is here; more info is here. Articles here.
There is a general security problem illustrated here: it is very difficult to secure data when the attacker has physical control of the machine the data is stored on. I talk about the general problem here, and it’s a hard problem.
EDITED TO ADD (2/26): How-to, with pictures.
Mujahideen Secrets 2 is a new version of an encryption tool, ostensibly written to help Al Qaeda members encrypt secrets as they communicate on the Internet.
A bunch of sites have covered this story, and a couple of security researchers are quoted in the various articles. But quotes like this make you wonder if they have any idea what they’re talking about:
Mujahideen Secrets 2 is a very compelling piece of software, from an encryption perspective, according to Henry. He said the new tool is easy to use and provides 2,048-bit encryption, an improvement over the 256-bit AES encryption supported in the original version.
No one has explained why a terrorist would use this instead of PGP—perhaps they simply don’t trust anything coming from a U.S. company. But honestly, this isn’t a big deal at all: strong encryption software has been around for over fifteen years now, either cheap or free. And the NSA probably breaks most of the stuff by guessing the password, anyway. Unless the whole program is an NSA plant, that is.
My question: the articles claim that the program uses several encryption algorithms, including RSA and AES. Does it use Blowfish or Twofish?
Oops:
The daily newspaper, Aftonbladet, turned the stick over to the Armed Forces on Thursday. The paper’s editorial office obtained the memory stick from an individual who discovered it in a public computer center in Stockholm.
An employee of the Armed Forces has reported that the misplaced USB memory stick belongs to him. The employee contacted his superior on Friday and divulged that he had forgotten the memory stick in a public computer. A preliminary technical investigation confirms that the stick belongs to the employee.
The stick contained both unclassified and classified information such as information regarding IED and mine threats in Afghanistan.
I wrote about this sort of thing two years ago:
The point is that it’s now amazingly easy to lose an enormous amount of information. Twenty years ago, someone could break into my office and copy every customer file, every piece of correspondence, everything about my professional life. Today, all he has to do is steal my computer. Or my portable backup drive. Or my small stack of DVD backups. Furthermore, he could sneak into my office and copy all this data, and I’d never know it.
Also this. Although why the Swedish Army doesn’t encrypt its portable storage devices is beyond me.
Computer security is hard. Software, computer and network security are all ongoing battles between attacker and defender. And in many cases the attacker has an inherent advantage: He only has to find one network flaw, while the defender has to find and fix every flaw.
Cryptography is an exception. As long as you don’t write your own algorithm, secure encryption is easy. And the defender has an inherent mathematical advantage: Longer keys increase the amount of work the defender has to do linearly, while geometrically increasing the amount of work the attacker has to do.
Unfortunately, cryptography can’t solve most computer-security problems. The one problem cryptography can solve is the security of data when it’s not in use. Encrypting files, archives—even entire disks—is easy.
All of this makes it even more amazing that Her Majesty’s Revenue & Customs in the United Kingdom lost two disks with personal data on 25 million British citizens, including dates of birth, addresses, bank-account information and national insurance numbers. On the one hand, this is no bigger a deal than any of the thousands of other exposures of personal data we’ve read about in recent years—the U.S. Veteran’s Administration loss of personal data of 26 million American veterans is an obvious similar event. But this has turned into Britain’s privacy Chernobyl.
Perhaps encryption isn’t so easy after all, and some people could use a little primer. This is how I protect my laptop.
There are several whole-disk encryption products on the market. I use PGP Disk’s Whole Disk Encryption tool for two reasons. It’s easy, and I trust both the company and the developers to write it securely. (Disclosure: I’m also on PGP Corp.’s Technical Advisory Board.)
Setup only takes a few minutes. After that, the program runs in the background. Everything works like before, and the performance degradation is negligible. Just make sure you choose a secure password—PGP’s encouragement of passphrases makes this much easier—and you’re secure against leaving your laptop in the airport or having it stolen out of your hotel room.
The reason you encrypt your entire disk, and not just key files, is so you don’t have to worry about swap files, temp files, hibernation files, erased files, browser cookies or whatever. You don’t need to enforce a complex policy about which files are important enough to be encrypted. And you have an easy answer to your boss or to the press if the computer is stolen: no problem; the laptop is encrypted.
PGP Disk can also encrypt external disks, which means you can also secure that USB memory device you’ve been using to transfer data from computer to computer. When I travel, I use a portable USB drive for backup. Those devices are getting physically smaller—but larger in capacity—every year, and by encrypting I don’t have to worry about losing them.
I recommend one more complication. Whole-disk encryption means that anyone at your computer has access to everything: someone at your unattended computer, a Trojan that infected your computer and so on. To deal with these and similar threats I recommend a two-tier encryption strategy. Encrypt anything you don’t need access to regularly—archived documents, old e-mail, whatever—separately, with a different password. I like to use PGP Disk’s encrypted zip files, because it also makes secure backup easier (and lets you secure those files before you burn them on a DVD and mail them across the country), but you can also use the program’s virtual-encrypted-disk feature to create a separately encrypted volume. Both options are easy to set up and use.
There are still two scenarios you aren’t secure against, though. You’re not secure against someone snatching your laptop out of your hands as you’re typing away at the local coffee shop. And you’re not secure against the authorities telling you to decrypt your data for them.
The latter threat is becoming more real. I have long been worried that someday, at a border crossing, a customs official will open my laptop and ask me to type in my password. Of course I could refuse, but the consequences might be severe—and permanent. And some countries—the United Kingdom, Singapore, Malaysia—have passed laws giving police the authority to demand that you divulge your passwords and encryption keys.
To defend against both of these threats, minimize the amount of data on your laptop. Do you really need 10 years of old e-mails? Does everyone in the company really need to carry around the entire customer database? One of the most incredible things about the Revenue & Customs story is that a low-level government employee mailed a copy of the entire national child database to the National Audit Office in London. Did he have to? Doubtful. The best defense against data loss is to not have the data in the first place.
Failing that, you can try to convince the authorities that you don’t have the encryption key. This works better if it’s a zipped archive than the whole disk. You can argue that you’re transporting the files for your boss, or that you forgot the key long ago. Make sure the time stamp on the files matches your claim, though.
There are other encryption programs out there. If you’re a Windows Vista user, you might consider BitLocker. This program, embedded in the operating system, also encrypts the computer’s entire drive. But it only works on the C: drive, so it won’t help with external disks or USB tokens. And it can’t be used to make encrypted zip files. But it’s easy to use, and it’s free.
This essay previously appeared on Wired.com.
EDITED TO ADD (12/14): Lots of people have pointed out that the free and open-source program TrueCrypt is a good alternative to PGP Disk. I haven’t used or reviewed the program at all.
In the UK:
In early November about 30 animal rights activists are understood to have received letters from the Crown Prosecution Service in Hampshire inviting them to provide passwords that will decrypt material held on seized computers.
The letter is the first stage of a process set out under RIPA which governs how the authorities handle requests to examine encrypted material.
Once a request has been issued the authorities can then issue what is known as a Section 49 notice demanding that a person turn the data into an “intelligible” form or, under Section 51 hand over keys.
Although much of RIPA came into force many years ago, the part governing the handing over of keys only passed in to law on 1 October 2007. This is why the CPS is only now asking for access to files on the seized machines.
Alongside a S49 notice, the authorities can also issue a Section 54 notice that prevents a person revealing that they are subject to this part of RIPA.
Actually, we don’t know if the activists actually handed the police their encryption keys yet. More about the law here.
If you remember, this was sold to the public as essential for fighting terrorism. It’s already being misused.
Sidebar photo of Bruce Schneier by Joe MacInnis.