Entries Tagged "TrueCrypt"

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ISIS Encryption Opsec

Tidbits from the New York Times:

The final phase of Mr. Hame’s training took place at an Internet cafe in Raqqa, where an Islamic State computer specialist handed him a USB key. It contained CCleaner, a program used to erase a user’s online history on a given computer, as well as TrueCrypt, an encryption program that was widely available at the time and that experts say has not yet been cracked.

[…]

More than a year and a half earlier, the would-be Cannes bomber, Ibrahim Boudina, had tried to erase the previous three days of his search history, according to details in his court record, but the police were still able to recover it. They found that Mr. Boudina had been researching how to connect to the Internet via a secure tunnel and how to change his I.P. address.

Though he may have been aware of the risk of discovery, perhaps he was not worried enough.

Mr. Boudina had been sloppy enough to keep using his Facebook account, and his voluminous chat history allowed French officials to determine his allegiance to the Islamic State. Wiretaps of his friends and relatives, later detailed in French court records obtained by The Times and confirmed by security officials, further outlined his plot, which officials believe was going to target the annual carnival on the French Riviera.

Mr. Hame, in contrast, was given strict instructions on how to communicate. After he used TrueCrypt, he was to upload the encrypted message folder onto a Turkish commercial data storage site, from where it would be downloaded by his handler in Syria. He was told not to send it by email, most likely to avoid generating the metadata that records details like the point of origin and destination, even if the content of the missive is illegible. Mr. Hame described the website as “basically a dead inbox.”

The ISIS technician told Mr. Hame one more thing: As soon as he made it back to Europe, he needed to buy a second USB key, and transfer the encryption program to it. USB keys are encoded with serial numbers, so the process was not unlike a robber switching getaway cars.

“He told me to copy what was on the key and then throw it away,” Mr. Hame explained. “That’s what I did when I reached Prague.”

Mr. Abaaoud was also fixated on cellphone security. He jotted down the number of a Turkish phone that he said would be left in a building in Syria, but close enough to the border to catch the Turkish cell network, according to Mr. Hame’s account. Mr. Abaaoud apparently figured investigators would be more likely to track calls from Europe to Syrian phone numbers, and might overlook calls to a Turkish one.

Next to the number, Mr. Abaaoud scribbled “Dad.”

This seems like exactly the sort of opsec I would set up for an insurgent group.

EDITED TO ADD: Mistakes in the article. For example:

And now I’ve read one of the original French documents and confirmed my suspicion that the NYTimes article got details wrong.

The original French uses the word “boîte”, which matches the TrueCrypt term “container”. The original French didn’t use the words “fichier” (file), “dossier” (folder), or “répertoire” (directory). This makes so much more sense, and gives us more confidence we know what they were doing.

The original French uses the term “site de partage”, meaning a “sharing site”, which makes more sense than a “storage” site.

The document I saw says the slip of paper had login details for the file sharing site, not a TrueCrypt password. Thus, when the NYTimes article says “TrueCrypt login credentials”, we should correct it to “file sharing site login credentials”, not “TrueCrypt passphrase”.

MOST importantly, according the subject, the login details didn’t even work. It appears he never actually used this method — he was just taught how to use it. He no longer remembers the site’s name, other than it might have the word “share” in its name. We see this a lot: ISIS talks a lot about encryption, but the evidence of them actually using it is scant.

Posted on March 31, 2016 at 6:10 AMView Comments

Encrypting Windows Hard Drives

Encrypting your Windows hard drives is trivially easy; choosing which program to use is annoyingly difficult. I still use Windows — yes, I know, don’t even start — and have intimate experience with this issue.

Historically, I used PGP Disk. I used it because I knew and trusted the designers. I even used it after Symantec bought the company. But big companies are always suspect, because there are a lot of ways for governments to manipulate them.

Then, I used TrueCrypt. I used it because it was open source. But the anonymous developers weirdly abdicated in 2014 when Microsoft released Windows 8. I stuck with the program for a while, saying:

For Windows, the options are basically BitLocker, Symantec’s PGP Disk, and TrueCrypt. I choose TrueCrypt as the least bad of all the options.

But soon after that, despite the public audit of TrueCrypt, I bailed for BitLocker.

BitLocker is Microsoft’s native file encryption program. Yes, it’s from a big company. But it was designed by my colleague and friend Niels Ferguson, whom I trust. (Here’s Niels’s statement from 2006 on back doors.) It was a snap decision; much had changed since 2006. (Here I am in March speculating about an NSA back door in BitLocker.) Specifically, Microsoft made a bunch of changes in BitLocker for Windows 8, including removing something Niels designed called the “Elephant Diffuser.”

The Intercept’s Micah Lee recently recommended BitLocker and got a lot of pushback from the security community. Last week, he published more research and explanation about the trade-offs. It’s worth reading. Microsoft told him they removed the Elephant Diffuser for performance reasons. And I agree with his ultimate conclusion:

Based on what I know about BitLocker, I think it’s perfectly fine for average Windows users to rely on, which is especially convenient considering it comes with many PCs. If it ever turns out that Microsoft is willing to include a backdoor in a major feature of Windows, then we have much bigger problems than the choice of disk encryption software anyway.

Whatever you choose, if trusting a proprietary operating system not to be malicious doesn’t fit your threat model, maybe it’s time to switch to Linux.

Micah also nicely explains how TrueCrypt is becoming antiquated, and not keeping up with Microsoft’s file system changes.

Lately, I am liking an obscure program called BestCrypt, by a Finnish company called Jetico. Micah quotes me:

Considering Schneier has been outspoken for decades about the importance of open source cryptography, I asked if he recommends that other people use BestCrypt, even though it’s proprietary. “I do recommend BestCrypt,” Schneier told me, “because I have met people at the company and I have a good feeling about them. Of course I don’t know for sure; this business is all about trust. But right now, given what I know, I trust them.”

I know it’s not a great argument. But, again, I’m trying to find the least bad option. And in the end, you either have to write your own software or trust someone else to write it for you.

But, yes, this should be an easier decision.

Posted on June 15, 2015 at 6:31 AMView Comments

Air Gaps

Since I started working with Snowden’s documents, I have been using a number of tools to try to stay secure from the NSA. The advice I shared included using Tor, preferring certain cryptography over others, and using public-domain encryption wherever possible.

I also recommended using an air gap, which physically isolates a computer or local network of computers from the Internet. (The name comes from the literal gap of air between the computer and the Internet; the word predates wireless networks.)

But this is more complicated than it sounds, and requires explanation.

Since we know that computers connected to the Internet are vulnerable to outside hacking, an air gap should protect against those attacks. There are a lot of systems that use — or should use — air gaps: classified military networks, nuclear power plant controls, medical equipment, avionics, and so on.

Osama Bin Laden used one. I hope human rights organizations in repressive countries are doing the same.

Air gaps might be conceptually simple, but they’re hard to maintain in practice. The truth is that nobody wants a computer that never receives files from the Internet and never sends files out into the Internet. What they want is a computer that’s not directly connected to the Internet, albeit with some secure way of moving files on and off.

But every time a file moves back or forth, there’s the potential for attack.

And air gaps have been breached. Stuxnet was a US and Israeli military-grade piece of malware that attacked the Natanz nuclear plant in Iran. It successfully jumped the air gap and penetrated the Natanz network. Another piece of malware named agent.btz, probably Chinese in origin, successfully jumped the air gap protecting US military networks.

These attacks work by exploiting security vulnerabilities in the removable media used to transfer files on and off the air-gapped computers.

Since working with Snowden’s NSA files, I have tried to maintain a single air-gapped computer. It turned out to be harder than I expected, and I have ten rules for anyone trying to do the same:

  1. When you set up your computer, connect it to the Internet as little as possible. It’s impossible to completely avoid connecting the computer to the Internet, but try to configure it all at once and as anonymously as possible. I purchased my computer off-the-shelf in a big box store, then went to a friend’s network and downloaded everything I needed in a single session. (The ultra-paranoid way to do this is to buy two identical computers, configure one using the above method, upload the results to a cloud-based anti-virus checker, and transfer the results of that to the air gap machine using a one-way process.)

  2. Install the minimum software set you need to do your job, and disable all operating system services that you won’t need. The less software you install, the less an attacker has available to exploit. I downloaded and installed OpenOffice, a PDF reader, a text editor, TrueCrypt, and BleachBit. That’s all. (No, I don’t have any inside knowledge about TrueCrypt, and there’s a lot about it that makes me suspicious. But for Windows full-disk encryption it’s that, Microsoft’s BitLocker, or Symantec’s PGPDisk — and I am more worried about large US corporations being pressured by the NSA than I am about TrueCrypt.)

  3. Once you have your computer configured, never directly connect it to the Internet again. Consider physically disabling the wireless capability, so it doesn’t get turned on by accident.

  4. If you need to install new software, download it anonymously from a random network, put it on some removable media, and then manually transfer it to the air-gapped computer. This is by no means perfect, but it’s an attempt to make it harder for the attacker to target your computer.

  5. Turn off all autorun features. This should be standard practice for all the computers you own, but it’s especially important for an air-gapped computer. Agent.btz used autorun to infect US military computers.

  6. Minimize the amount of executable code you move onto the air-gapped computer. Text files are best. Microsoft Office files and PDFs are more dangerous, since they might have embedded macros. Turn off all macro capabilities you can on the air-gapped computer. Don’t worry too much about patching your system; in general, the risk of the executable code is worse than the risk of not having your patches up to date. You’re not on the Internet, after all.

  7. Only use trusted media to move files on and off air-gapped computers. A USB stick you purchase from a store is safer than one given to you by someone you don’t know — or one you find in a parking lot.

  8. For file transfer, a writable optical disk (CD or DVD) is safer than a USB stick. Malware can silently write data to a USB stick, but it can’t spin the CD-R up to 1000 rpm without your noticing. This means that the malware can only write to the disk when you write to the disk. You can also verify how much data has been written to the CD by physically checking the back of it. If you’ve only written one file, but it looks like three-quarters of the CD was burned, you have a problem. Note: the first company to market a USB stick with a light that indicates a write operation — not read or write; I’ve got one of those — wins a prize.

  9. When moving files on and off your air-gapped computer, use the absolute smallest storage device you can. And fill up the entire device with random files. If an air-gapped computer is compromised, the malware is going to try to sneak data off it using that media. While malware can easily hide stolen files from you, it can’t break the laws of physics. So if you use a tiny transfer device, it can only steal a very small amount of data at a time. If you use a large device, it can take that much more. Business-card-sized mini-CDs can have capacity as low as 30 MB. I still see 1-GB USB sticks for sale.

  10. Consider encrypting everything you move on and off the air-gapped computer. Sometimes you’ll be moving public files and it won’t matter, but sometimes you won’t be, and it will. And if you’re using optical media, those disks will be impossible to erase. Strong encryption solves these problems. And don’t forget to encrypt the computer as well; whole-disk encryption is the best.

One thing I didn’t do, although it’s worth considering, is use a stateless operating system like Tails. You can configure Tails with a persistent volume to save your data, but no operating system changes are ever saved. Booting Tails from a read-only DVD — you can keep your data on an encrypted USB stick — is even more secure. Of course, this is not foolproof, but it greatly reduces the potential avenues for attack.

Yes, all this is advice for the paranoid. And it’s probably impossible to enforce for any network more complicated than a single computer with a single user. But if you’re thinking about setting up an air-gapped computer, you already believe that some very powerful attackers are after you personally. If you’re going to use an air gap, use it properly.

Of course you can take things further. I have met people who have physically removed the camera, microphone, and wireless capability altogether. But that’s too much paranoia for me right now.

This essay previously appeared on Wired.com.

EDITED TO ADD: Yes, I am ignoring TEMPEST attacks. I am also ignoring black bag attacks against my home.

Posted on October 11, 2013 at 6:45 AMView Comments

Breaking Hard-Disk Encryption

The newly announced ElcomSoft Forensic Disk Decryptor can decrypt BitLocker, PGP, and TrueCrypt. And it’s only $300. How does it work?

Elcomsoft Forensic Disk Decryptor acquires the necessary decryption keys by analyzing memory dumps and/or hibernation files obtained from the target PC. You’ll thus need to get a memory dump from a running PC (locked or unlocked) with encrypted volumes mounted, via a standard forensic product or via a FireWire attack. Alternatively, decryption keys can also be derived from hibernation files if a target PC is turned off.

This isn’t new. I wrote about AccessData doing the same thing in 2007:

Even so, none of this might actually matter. AccessData sells another program, Forensic Toolkit, that, among other things, scans a hard drive for every printable character string. It looks in documents, in the Registry, in e-mail, in swap files, in deleted space on the hard drive … everywhere. And it creates a dictionary from that, and feeds it into PRTK.

And PRTK breaks more than 50 percent of passwords from this dictionary alone.

It’s getting harder and harder to maintain good file security.

Posted on December 27, 2012 at 1:02 PMView Comments

Information-Age Law Enforcement Techniques

This is an interesting blog post:

Buried inside a recent United Nations Office on Drugs and Crime report titled Use of Internet for Terrorist Purposes one can carve out details and examples of law enforcement electronic surveillance techniques that are normally kept secret.

[…]

Point 280: International members of the guerilla group Revolutionary Armed Forces of Colombia (FARC) communicated with their counterparts hiding messages inside images with steganography and sending the emails disguised as spam, deleting Internet browsing cache afterwards to make sure that the authorities would not get hold of the data. Spanish and Colombian authorities cooperated to break the encryption keys and successfully deciphered the messages.

[…]

Point 198: It explains how an investigator can circumvent Truecrypt plausible deniability feature (hidden container), advising computer forensics investigators to take into consideration during the computer analysis to check if there is any missing volume of data.

[…]

Point 210: Explains how Remote Administration Trojans (RATs) can be introduced into a suspects computer to collect data or control his computer and it makes reference to hardware and software keyloggers as well as packet sniffers.

There’s more at the above link. Here’s the final report.

Posted on December 19, 2012 at 6:47 AMView Comments

TrueCrypt's Deniable File System

Together with Tadayoshi Kohno, Steve Gribble, and three of their students at the University of Washington, I have a new paper that breaks the deniable encryption feature of TrueCrypt version 5.1a. Basically, modern operating systems leak information like mad, making deniability a very difficult requirement to satisfy.

ABSTRACT: We examine the security requirements for creating a Deniable File System (DFS), and the efficacy with which the TrueCrypt disk-encryption software meets those requirements. We find that the Windows Vista operating system itself, Microsoft Word, and Google Desktop all compromise the deniability of a TrueCrypt DFS. While staged in the context of TrueCrypt, our research highlights several fundamental challenges to the creation and use of any DFS: even when the file system may be deniable in the pure, mathematical sense, we find that the environment surrounding that file system can undermine its deniability, as well as its contents. Finally, we suggest approaches for overcoming these challenges on modern operating systems like Windows.

The students did most of the actual work. I helped with the basic ideas, and contributed the threat model. Deniability is a very hard feature to achieve.

There are several threat models against which a DFS could potentially be secure:

  • One-Time Access. The attacker has a single snapshot of the disk image. An example would be when the secret police seize Alice’s computer.
  • Intermittent Access. The attacker has several snapshots of the disk image, taken at different times. An example would be border guards who make a copy of Alice’s hard drive every time she enters or leaves the country.
  • Regular Access. The attacker has many snapshots of the disk image, taken in short intervals. An example would be if the secret police break into Alice’s apartment every day when she is away, and make a copy of the disk each time.

Since we wrote our paper, TrueCrypt released version 6.0 of its software, which claims to have addressed many of the issues we’ve uncovered. In the paper, we said:

We analyzed the most current version of TrueCrypt available at the writing of the paper, version 5.1a. We shared a draft of our paper with the TrueCrypt development team in May 2008. TrueCrypt version 6.0 was released in July 2008. We have not analyzed version 6.0, but observe that TrueCrypt v6.0 does take new steps to improve TrueCrypt’s deniability properties (e.g., via the creation of deniable operating systems, which we also recommend in Section 5). We suggest that the breadth of our results for TrueCrypt v5.1a highlight the challenges to creating deniable file systems. Given these potential challenges, we encourage the users not to blindly trust the deniability of such systems. Rather, we encourage further research evaluating the deniability of such systems, as well as research on new yet light-weight methods for improving deniability.

So we cannot break the deniability feature in TrueCrypt 6.0. But, honestly, I wouldn’t trust it.

There have been two news articles (and a Slashdot thread) about the paper.

One talks about a generalization to encrypted partitions. If you don’t encrypt the entire drive, there is the possibility — and it seems very probable — that information about the encrypted partition will leak onto the unencrypted rest of the drive. Whole disk encryption is the smartest option.

Our paper will be presented at the 3rd USENIX Workshop on Hot Topics in Security (HotSec ’08). I’ve written about deniability before.

Posted on July 18, 2008 at 6:56 AMView Comments

How to Secure Your Computer, Disks, and Portable Drives

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.

Posted on December 4, 2007 at 6:40 AMView Comments

Sidebar photo of Bruce Schneier by Joe MacInnis.