Entries Tagged "cryptography"

Page 34 of 56

New Attack Against ASP.NET

It’s serious:

The problem lies in the way that ASP.NET, Microsoft’s popular Web framework, implements the AES encryption algorithm to protect the integrity of the cookies these applications generate to store information during user sessions. A common mistake is to assume that encryption protects the cookies from tampering so that if any data in the cookie is modified, the cookie will not decrypt correctly. However, there are a lot of ways to make mistakes in crypto implementations, and when crypto breaks, it usually breaks badly.

“We knew ASP.NET was vulnerable to our attack several months ago, but we didn’t know how serious it is until a couple of weeks ago. It turns out that the vulnerability in ASP.NET is the most critical amongst other frameworks. In short, it totally destroys ASP.NET security,” said Thai Duong, who along with Juliano Rizzo, developed the attack against ASP.NET.

Here’s a demo of the attack, and the Microsoft Security Advisory. More articles. The theory behind this attack is here.

EDITED TO ADD (9/27): Three blog posts from Scott Guthrie.

EDITED TO ADD (9/28): There’s a patch.

EDITED TO ADD (10/13): Two more articles.

Posted on September 27, 2010 at 6:51 AM • View Comments

UAE Man-in-the-Middle Attack Against SSL

Interesting:

Who are these certificate authorities? At the beginning of Web history, there were only a handful of companies, like Verisign, Equifax, and Thawte, that made near-monopoly profits from being the only providers trusted by Internet Explorer or Netscape Navigator. But over time, browsers have trusted more and more organizations to verify Web sites. Safari and Firefox now trust more than 60 separate certificate authorities by default. Microsoft’s software trusts more than 100 private and government institutions.

Disturbingly, some of these trusted certificate authorities have decided to delegate their powers to yet more organizations, which aren’t tracked or audited by browser companies. By scouring the Net for certificates, security researchers have uncovered more than 600 groups who, through such delegation, are now also automatically trusted by most browsers, including the Department of Homeland Security, Google, and Ford Motors­and a UAE mobile phone company called Etisalat.

In 2005, a company called CyberTrust­—which has since been purchased by Verizon­—gave Etisalat, the government-connected mobile company in the UAE, the right to verify that a site is valid. Here’s why this is trouble: Since browsers now automatically trust Etisalat to confirm a site’s identity, the company has the potential ability to fake a secure connection to any site Etisalat subscribers might visit using a man-in-the-middle scheme.

EDITED TO ADD (9/14): EFF has gotten involved.

Posted on September 3, 2010 at 6:27 AM • View Comments

Successful Attack Against a Quantum Cryptography System

Clever:

Quantum cryptography is often touted as being perfectly secure. It is based on the principle that you cannot make measurements of a quantum system without disturbing it. So, in theory, it is impossible for an eavesdropper to intercept a quantum encryption key without disrupting it in a noticeable way, triggering alarm bells.

Vadim Makarov at the Norwegian University of Science and Technology in Trondheim and his colleagues have now cracked it. “Our hack gave 100% knowledge of the key, with zero disturbance to the system,” he says.

[…]

The cunning part is that while blinded, Bob’s detector cannot function as a ‘quantum detector’ that distinguishes between different quantum states of incoming light. However, it does still work as a ‘classical detector’ ­ recording a bit value of 1 if it is hit by an additional bright light pulse, regardless of the quantum properties of that pulse.

That means that every time Eve intercepts a bit value of 1 from Alice, she can send a bright pulse to Bob, so that he also receives the correct signal, and is entirely unaware that his detector has been sabotaged. There is no mismatch between Eve and Bob’s readings because Eve sends Bob a classical signal, not a quantum one. As quantum cryptographic rules no longer apply, no alarm bells are triggered, says Makarov.

“We have exploited a purely technological loophole that turns a quantum cryptographic system into a classical system, without anyone noticing,” says Makarov.

Makarov and his team have demonstrated that the hack works on two commercially available systems: one sold by ID Quantique (IDQ), based in Geneva, Switzerland, and one by MagiQ Technologies, based in Boston, Massachusetts. “Once I had the systems in the lab, it took only about two months to develop a working hack,” says Makarov.

Just because something is secure in theory doesn’t mean it’s secure in practice. Or, to put it more cleverly: in theory, theory and practice are the same; but in practice, they’re very different.

The paper is here.

Posted on September 2, 2010 at 1:46 PM • View Comments

Wanted: Skein Hardware Help

As part of NIST’s SHA-3 selection process, people have been implementing the candidate hash functions on a variety of hardware and software platforms. Our team has implemented Skein in Intel’s 32 nm ASIC process, and got some impressive performance results (presentation and paper). Several other groups have implemented Skein in FPGA and ASIC, and have seen significantly poorer performance. We need help understanding why.

For example, a group led by Brian Baldwin at the Claude Shannon Institute for Discrete Mathematics, Coding and Cryptography implemented all the second-round candidates in FPGA (presentation and paper). Skein performance was terrible, but when they checked their code, they found an error. Their corrected performance comparison (presentation and paper) has Skein performing much better and in the top ten.

We suspect that the adders in all the designs may not be properly optimized, although there may be other performance issues. If we can at least identify (or possibly even fix) the slowdowns in the design, it would be very helpful, both for our understanding and for Skein’s hardware profile. Even if we find that the designs are properly optimized, that would also be good to know.

A group at George Mason University led by Kris Gaj implemented all the second-round candidates in FPGA (presentation, paper, and much longer paper). Skein had the worst performance of any of the implementations. We’re looking for someone who can help us understand the design, and determine if it can be improved.

Another group, led by Stefan Tillich at University of Bristol, implemented all the candidates in 180 nm custom ASIC (presentation and paper). Here, Skein is one of the worst performers. We’re looking for someone who can help us understand what this group did.

Three other groups—one led by Patrick Schaumont of Virginia Tech (presentation and paper), another led by Shin’ichiro Matsuo at National Institute of Information and Communications Technology in Japan (presentation and paper), and a third led by Luca Henzen at ETH Zurich (paper with appendix, and conference version)—implemented the SHA-3 candidates. Again, we need help understanding how their Skein performance numbers are so different from ours.

We’re looking for people with FPGA and ASIC skills to work with the Skein team. We don’t have money to pay anyone; co-authorship on a paper (and a Skein polo shirt) is our primary reward. Please send me e-mail if you’re interested.

Posted on September 1, 2010 at 1:17 PM • View Comments

More Skein News

Skein is my new hash function. Well, “my” is an overstatement; I’m one of the eight designers. It was submitted to NIST for their SHA-3 competition, and one of the 14 algorithms selected to advance to the second round. Here’s the Skein paper; source code is here. The Skein website is here.

Last week was the Second SHA-3 Candidate Conference. Lots of people presented papers on the candidates: cryptanalysis papers, implementation papers, performance comparisons, etc. There were two cryptanalysis papers on Skein. The first was by Kerry McKay and Poorvi L. Vora (presentation and paper). They tried to extend linear cryptanalysis to groups of bits to attack Threefish (the block cipher inside Skein). It was a nice analysis, but it didn’t get very far at all.

The second was a fantastic piece of cryptanalysis by Dmitry Khovratovich, Ivica Nikolié, and Christian Rechberger. They used a rotational rebound attack (presentation and paper) to mount a “known-key distinguisher attack” on 57 out of 72 Threefish rounds faster than brute force. It’s a new type of attack—some go so far as to call it an “observation”—and the community is still trying to figure out what it means. It only works if the attacker can manipulate both the plaintexts and the keys in a structured way. Against 57-round Threefish, it requires 2503 work—barely better than brute force. And it only distinguishes reduced-round Threefish from a random permutation; it doesn’t actually recover any key bits.

Even with the attack, Threefish has a good security margin. Also, the attack doesn’t affect Skein. But changing one constant in the algorithm’s key schedule makes the attack impossible. NIST has said they’re allowing second-round tweaks, so we’re going to make the change. It won’t affect any performance numbers or obviate any other cryptanalytic results—but the best attack would be 33 out of 72 rounds.

Our update on Skein, which we presented at the conference, is here. All the other papers and presentations are here. (My 2008 essay on SHA-3 is here, and my 2009 update is here.) The second-round algorithms are: BLAKE, Blue Midnight Wish, CubeHash, ECHO, Fugue, Grøstl, Hamsi, JH, Keccak, Luffa, Shabal, SHAvite-3, SIMD, and Skein. You can find details on all of them, as well as the current state of their cryptanalysis, here. NIST will select approximately five algorithms to go on to the third round by the end of the year.

In other news, we’re once again making Skein polo shirts available to the public. Those of you who attended either of the two SHA-3 conferences might have noticed the stylish black Skein polo shirts worn by the Skein team. Anyone who wants one is welcome to buy it, at cost. Details (with photos) are here. All orders must be received before October 1, and we’ll have all the shirts made in one batch.

Posted on September 1, 2010 at 6:01 AM • View Comments

Eavesdropping on Smart Homes with Distributed Wireless Sensors

“Protecting your daily in-home activity information from a wireless snooping attack,” by Vijay Srinivasan, John Stankovic, and Kamin Whitehouse:

Abstract: In this paper, we first present a new privacy leak in residential wireless ubiquitous computing systems, and then we propose guidelines for designing future systems to prevent this problem. We show that we can observe private activities in the home such as cooking, showering, toileting, and sleeping by eavesdropping on the wireless transmissions of sensors in a home, even when all of the transmissions are encrypted. We call this the Fingerprint and Timing-based Snooping (FATS) attack. This attack can already be carried out on millions of homes today, and may become more important as ubiquitous computing environments such as smart homes and assisted living facilities become more prevalent. In this paper, we demonstrate and evaluate the FATS attack on eight different homes containing wireless sensors. We also propose and evaluate a set of privacy preserving design guidelines for future wireless ubiquitous systems and show how these guidelines can be used in a hybrid fashion to prevent against the FATS attack with low implementation costs.

The group was able to infer surprisingly detailed activity information about the residents, including when they were home or away, when they were awake or sleeping, and when they were performing activities such as showering or cooking. They were able to infer all this without any knowledge of the location, semantics, or source identifier of the wireless sensors, while assuming perfect encryption of the data and source identifiers.

Posted on August 31, 2010 at 12:39 PM • View Comments

Location-Based Quantum Encryption

Location-based encryption—a system by which only a recipient in a specific location can decrypt the message—fails because location can be spoofed. Now a group of researchers has solved the problem in a quantum cryptography setting:

The research group has recently shown that if one sends quantum bits—the quantum equivalent of a bit—instead of only classical bits, a secure protocol can be obtained such that the location of a device cannot be spoofed. This, in turn, leads to a key-exchange protocol based solely on location.

The core idea behind the protocol is the “no-cloning” principle of quantum mechanics. By making a device give the responses of random challenges to several verifiers, the protocol ensures that multiple colluding devices cannot falsely prove any location. This is because an adversarial device can either store the quantum state of the challenge or send it to a colluding adversary, but not both.

Don’t expect this in a product anytime soon. Quantum cryptography is mostly theoretical and almost entirely laboratory-only. But as research, it’s great stuff. Paper here.

Posted on August 3, 2010 at 6:25 AM • View Comments

DNSSEC Root Key Split Among Seven People

The DNSSEC root key has been divided among seven people:

Part of ICANN’s security scheme is the Domain Name System Security, a security protocol that ensures Web sites are registered and “signed” (this is the security measure built into the Web that ensures when you go to a URL you arrive at a real site and not an identical pirate site). Most major servers are a part of DNSSEC, as it’s known, and during a major international attack, the system might sever connections between important servers to contain the damage.

A minimum of five of the seven keyholders—one each from Britain, the U.S., Burkina Faso, Trinidad and Tobago, Canada, China, and the Czech Republic—would have to converge at a U.S. base with their keys to restart the system and connect everything once again.

That’s a secret sharing scheme they’re using, most likely Shamir’s Secret Sharing.
We know the names of some of them.

Paul Kane—who lives in the Bradford-on-Avon area—has been chosen to look after one of seven keys, which will ‘restart the world wide web’ in the event of a catastrophic event.

Dan Kaminsky is another.

I don’t know how they picked those countries.

Posted on July 28, 2010 at 11:12 AM • View Comments

WPA Cracking in the Cloud

It’s a service:

The mechanism used involves captured network traffic, which is uploaded to the WPA Cracker service and subjected to an intensive brute force cracking effort. As advertised on the site, what would be a five-day task on a dual-core PC is reduced to a job of about twenty minutes on average. For the more “premium” price of $35, you can get the job done in about half the time. Because it is a dictionary attack using a predefined 135-million-word list, there is no guarantee that you will crack the WPA key, but such an extensive dictionary attack should be sufficient for any but the most specialized penetration testing purposes.

[…]

It gets even better. If you try the standard 135-million-word dictionary and do not crack the WPA encryption on your target network, there is an extended dictionary that contains an additional 284 million words. In short, serious brute force wireless network encryption cracking has become a retail commodity.

FAQ here.

In related news, there might be a man-in-the-middle attack possible against the WPA2 protocol. Man-in-the-middle attacks are potentially serious, but it depends on the details—and they’re not available yet.

EDITED TO ADD (8/8): Details about the MITM attack.

Posted on July 27, 2010 at 6:43 AM • View Comments

1 … 32 33 34 35 36 … 56

Sidebar photo of Bruce Schneier by Joe MacInnis.