David Kahn Donates his Cryptography Collection to the National Cryptologic Museum
I think that’s where my collection will be going, too.
Entries Tagged "cryptography"
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Kahn, Diffie, Clark, and Me at Bletchley Park
Saturday, I visited Bletchley Park to speak at the Annual ACCU Security Fundraising Conference. They had a stellar line of speakers this year, and I was pleased to be a part of the day.
Talk #1: “The Art of Forensic Warfare,” Andy Clark. Riffing on Sun Tzu’s The Art of War, Clark discussed the war—the back and forth—between cyber attackers and cyber forensics. This isn’t to say that we’re at war, but today’s attacker tactics are increasingly sophisticated and warlike. Additionally, the pace is greater, the scale of impact is greater, and the subjects of attack are broader. To defend ourselves, we need to be equally sophisticated and—possibly—more warlike.
Clark drew parallels from some of the chapters of Sun Tzu’s book combined with examples of the work at Bletchley Park. Laying plans: when faced with an attacker—especially one of unknown capabilities, tactics, and motives—it’s important to both plan ahead and plan for the unexpected. Attack by stratagem: increasingly, attackers are employing complex and long-term strategies; defenders need to do the same. Energy: attacks increasingly start off simple and get more complex over time; while it’s easier to defect primary attacks, secondary techniques tend to be more subtle and harder to detect. Terrain: modern attacks take place across a very broad range of terrain, including hardware, OSs, networks, communication protocols, and applications. The business environment under attack is another example of terrain, equally complex. The use of spies: not only human spies, but also keyloggers and other embedded eavesdropping malware. There’s a great World War II double-agent story about Eddie Chapman, codenamed ZIGZAG.
Talk #2: “How the Allies Suppressed the Second Greatest Secret of World War II,” David Kahn. This talk is from Kahn’s article of the same name, published in the Oct 2010 issue of The Journal of Military History. The greatest secret of World War II was the atom bomb; the second greatest secret was that the Allies were reading the German codes. But while there was a lot of public information in the years after World War II about Japanese codebreaking and its value, there was almost nothing about German codebreaking. Kahn discussed how this information was suppressed, and how historians writing World War II histories never figured it out. No one imagined as large and complex an operation as Bletchley Park; it was the first time in history that something like this had ever happened. Most of Kahn’s time was spent in a very interesting Q&A about the history of Bletchley Park and World War II codebreaking.
Talk #3: “DNSSec, A System for Improving Security of the Internet Domain Name System,” Whitfield Diffie. Whit talked about three watersheds in modern communications security. The first was the invention of the radio. Pre-radio, the most common communications security device was the code book. This was no longer enough when radio caused the amount of communications to explode. In response, inventors took the research in Vigenère ciphers and automated them. This automation led to an explosion of designs and an enormous increase in complexity—and the rise of modern cryptography.
The second watershed was shared computing. Before the 1960s, the security of computers was the physical security of computer rooms. Timesharing changed that. The result was computer security, a much harder problem than cryptography. Computer security is primarily the problem of writing good code. But writing good code is hard and expensive, so functional computer security is primarily the problem of dealing with code that isn’t good. Networking—and the Internet—isn’t just an expansion of computing capacity. The real difference is how cheap it is to set up communications connections. Setting up these connections requires naming: both IP addresses and domain names. Security, of course, is essential for this all to work; DNSSec is a critical part of that.
The third watershed is cloud computing, or whatever you want to call the general trend of outsourcing computation. Google is a good example. Every organization uses Google search all the time, which probably makes it the most valuable intelligence stream on the planet. How can you protect yourself? You can’t, just as you can’t whenever you hand over your data for storage or processing—you just have to trust your outsourcer. There are two solutions. The first is legal: an enforceable contract that protects you and your data. The second is technical, but mostly theoretical: homomorphic encryption that allows you to outsource computation of data without having to trust that outsourcer.
Diffie’s final point is that we’re entering an era of unprecedented surveillance possibilities. It doesn’t matter if people encrypt their communications, or if they encrypt their data in storage. As long as they have to give their data to other people for processing, it will be possible to eavesdrop on. Of course the methods will change, but the result will be an enormous trove of information about everybody.
Talk #4: “Reconceptualizing Security,” me. It was similar to this essay and this video.
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.
UAE Man-in-the-Middle Attack Against SSL
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.
Successful Attack Against a Quantum Cryptography System
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.
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.
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.
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.
P ≠ NP?
There’s a new paper circulating that claims to prove that P ≠ NP. The paper has not been refereed, and I haven’t seen any independent verifications or refutations. Despite the fact that the paper is by a respected researcher—HP Lab’s Vinay Deolalikar—and not a crank, my bet is that the proof is flawed.
EDITED TO ADD (8/16): Proof seems to be seriously flawed.
EDITED TO ADD (9/11): Proof is wrong.
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.
Sidebar photo of Bruce Schneier by Joe MacInnis.