Entries Tagged "encryption"

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Cryptocat

I’m late writing about this one. Cryptocat is a web-based encrypted chat application. After Wired published a pretty fluffy profile on the program and its author, security researcher Chris Soghoian wrote an essay criticizing the unskeptical coverage. Ryan Singel, the editor (not the writer) of the Wired piece, responded by defending the original article and attacking Soghoian.

At this point, I would have considered writing a long essay explaining what’s wrong with the whole concept behind Cryptocat, and echoing my complaints about the dangers of uncritically accepting the security claims of people and companies that write security software, but Patrick Ball did a great job:

CryptoCat is one of a whole class of applications that rely on what’s called “host-based security”. The most famous tool in this group is Hushmail, an encrypted e-mail service that takes the same approach. Unfortunately, these tools are subject to a well-known attack. I’ll detail it below, but the short version is if you use one of these applications, your security depends entirely the security of the host. This means that in practice, CryptoCat is no more secure than Yahoo chat, and Hushmail is no more secure than Gmail. More generally, your security in a host-based encryption system is no better than having no crypto at all.

Sometimes it’s nice to come in late.

EDITED TO ADD (8/14): As a result of this, CryptoCat is moving to a browser plug-in model.

Posted on August 14, 2012 at 6:00 AM • View Comments

Breaking Microsoft's PPTP Protocol

Some things never change. Thirteen years ago, Mudge and I published a paper breaking Microsoft’s PPTP protocol and the MS-CHAP authentication system. I haven’t been paying attention, but I presume it’s been fixed and improved over the years. Well, it’s been broken again.

ChapCrack can take captured network traffic that contains a MS-CHAPv2 network handshake (PPTP VPN or WPA2 Enterprise handshake) and reduce the handshake’s security to a single DES (Data Encryption Standard) key.

This DES key can then be submitted to CloudCracker.com—a commercial online password cracking service that runs on a special FPGA cracking box developed by David Hulton of Pico Computing—where it will be decrypted in under a day.

The CloudCracker output can then be used with ChapCrack to decrypt an entire session captured with WireShark or other similar network sniffing tools.

Posted on August 6, 2012 at 11:22 AM • View Comments

Changing Surveillance Techniques for Changed Communications Technologies

New paper by Peter P. Swire—”From Real-Time Intercepts to Stored Records: Why Encryption Drives the Government to Seek Access to the Cloud”:

Abstract: This paper explains how changing technology, especially the rising adoption of encryption, is shifting law enforcement and national security lawful access to far greater emphasis on stored records, notably records stored in the cloud. The major and growing reliance on surveillance access to stored records results from the following changes:

(1) Encryption. Adoption of strong encryption is becoming much more common for data and voice communications, via virtual private networks, encrypted webmail, SSL web sessions, and encrypted Voice over IP voice communications.

(2) Declining effectiveness of traditional wiretaps. Traditional wiretap techniques at the ISP or local telephone network increasingly encounter these encrypted communications, blocking the effectiveness of the traditional techniques.

(3) New importance of the cloud. Government access to communications thus increasingly relies on a new and limited set of methods, notably featuring access to stored records in the cloud.

(4) The “haves” and “have-nots.” The first three changes create a new division between the “haves” and “have-nots” when it comes to government access to communications. The “have-nots” become increasingly dependent, for access to communications, on cooperation from the “have” jurisdictions.

Part 1 of the paper describes the changing technology of wiretaps and government access. Part 2 documents the growing adoption of strong encryption in a wide and growing range of settings of interest to government agencies. Part 3 explains how these technological trends create a major shift from real-time intercepts to stored records, especially in the cloud.

Posted on June 11, 2012 at 6:36 AM • View Comments

U.S. Federal Court Rules that it Is Unconstitutional for the Police to Force Someone to Decrypt their Laptop

A U.S. Federal Court ruled that it is unconstitutional for the police to force someone to decrypt their laptop computer:

Thursday’s decision by the 11th U.S. Circuit Court of Appeals said that an encrypted hard drive is akin to a combination to a safe, and is off limits, because compelling the unlocking of either of them is the equivalent of forcing testimony.

Here’s the actual decision. And another blog post.

Note that this a different case, and an opposite ruling, than this. Although the legal experts say that the rulings are not actually in conflict:

Also note that the court’s analysis isn’t inconsistent with Boucher and Fricosu, the two district court cases on 5th Amendment limits on decryption. In both of those prior cases, the district courts merely held on the facts of the case that the testimony was a foregone conclusion.

Posted on February 27, 2012 at 5:49 AM • View Comments

Cryptanalysis of Satellite Phone Encryption Algorithms

From the abstract of the paper:

In this paper, we analyze the encryption systems used in the two existing (and competing) satphone standards, GMR-1 and GMR-2. The first main contribution is that we were able to completely reverse engineer the encryption algorithms employed. Both ciphers had not been publicly known previously. We describe the details of the recovery of the two algorithms from freely available DSP-firmware updates for satphones, which included the development of a custom disassembler and tools to analyze the code, and extending prior work on binary analysis to efficiently identify cryptographic code. We note that these steps had to be repeated for both systems, because the available binaries were from two entirely different DSP processors. Perhaps somewhat surprisingly, we found that the GMR-1 cipher can be considered a proprietary variant of the GSM A5/2 algorithm, whereas the GMR-2 cipher is an entirely new design. The second main contribution lies in the cryptanalysis of the two proprietary stream ciphers. We were able to adopt known A5/2 ciphertext-only attacks to the GMR-1 algorithm with an average case complexity of 232 steps. With respect to the GMR-2 cipher, we developed a new attack which is powerful in a known-plaintext setting. In this situation, the encryption key for one session, i.e., one phone call, can be recovered with approximately 50­65 bytes of key stream and a moderate computational complexity. A major finding of our work is that the stream ciphers of the two existing satellite phone systems are considerably weaker than what is state-oft-he-art in symmetric cryptography.

Press release. And news stories.

Posted on February 16, 2012 at 12:22 PM • View Comments

What Happens When the Court Demands You Decrypt a Document and You Forget the Key?

Last month, a U.S. court demanded that a defendent surrender the encryption key to a laptop so the police could examine it. Now it seems that she’s forgotten the key.

What happens now? It seems as if this excuse would always be available to someone who doesn’t want the police to decrypt her files. On the other hand, it might be hard to realistically forget a key. It’s less credible for someone to say “I have no idea what my password is,” and more likely to say something like “it was the word ‘telephone’ with a zero for the o and then some number following—four digits, with a six in it—and then a punctuation mark like a period.” And then a brute-force password search could be targeted. I suppose someone could say “it was a random alphanumeric password created by an automatic program; I really have no idea,” but I’m not sure a judge would believe it.

Posted on February 13, 2012 at 5:20 AM • View Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.