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Using Agent-Based Simulations to Evaluate Security Systems

Kay Hamacher and Stefan Katzenbeisser, “Public Security: Simulations Need to Replace Conventional Wisdom,” New Security Paradigms Workshop, 2011.

Abstract: Is more always better? Is conventional wisdom always the right guideline in the development of security policies that have large opportunity costs? Is the evaluation of security measures after their introduction the best way? In the past, these questions were frequently left unasked before the introduction of many public security measures. In this paper we put forward the new paradigm that agent-based simulations are an effective and most likely the only sustainable way for the evaluation of public security measures in a complex environment. As a case-study we provide a critical assessment of the power of Telecommunications Data Retention (TDR), which was introduced in most European countries, despite its huge impact on privacy. Up to now it is unknown whether TDR has any benefits in the identification of terrorist dark nets in the period before an attack. The results of our agent-based simulations suggest, contrary to conventional wisdom, that the current practice of acquiring more data may not necessarily yield higher identification rates.

Both the methodology and the conclusions are interesting.

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Posted on September 26, 2012 at 7:11 AM • View Comments

SHA-3 to Be Announced

NIST is about to announce the new hash algorithm that will become SHA-3. This is the result of a six-year competition, and my own Skein is one of the five remaining finalists (out of an initial 64).

It’s probably too late for me to affect the final decision, but I am hoping for “no award.”

It’s not that the new hash functions aren’t any good, it’s that we don’t really need one. When we started this process back in 2006, it looked as if we would be needing a new hash function soon. The SHA family (which is really part of the MD4 and MD5 family), was under increasing pressure from new types of cryptanalysis. We didn’t know how long the various SHA-2 variants would remain secure. But it’s 2012, and SHA-512 is still looking good.

Even worse, none of the SHA-3 candidates is significantly better. Some are faster, but not orders of magnitude faster. Some are smaller in hardware, but not orders of magnitude smaller. When SHA-3 is announced, I’m going to recommend that, unless the improvements are critical to their application, people stick with the tried and true SHA-512. At least for a while.

I don’t think NIST is going to announce “no award”; I think it’s going to pick one. And of the five remaining, I don’t really have a favorite. Of course I want Skein to win, but that’s out of personal pride, not for some objective reason. And while I like some more than others, I think any would be okay.

Well, maybe there’s one reason NIST should choose Skein. Skein isn’t just a hash function, it’s the large-block cipher Threefish and a mechanism to turn it into a hash function. I think the world actually needs a large-block cipher, and if NIST chooses Skein, we’ll get one.

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Posted on September 24, 2012 at 6:59 AM • View Comments

The NSA and the Risk of Off-the-Shelf Devices

Interesting article on how the NSA is approaching risk in the era of cool consumer devices. There’s a discussion of the president’s network-disabled iPad, and the classified cell phone that flopped because it took so long to develop and was so clunky. Turns out that everyone wants to use iPhones.

Levine concluded, “Using commercial devices to process classified phone calls, using commercial tablets to talk over wifi—that’s major game-changer for NSA to put classified information over wifi networks, but that’s what we’re going to do.” One way that would be done, he said, was by buying capability from cell carriers that have networks of cell towers in much the way small cell providers and companies like Onstar do.

Interestingly, Levine described an agency that is being forced to adopt a more realistic and practical attitude toward risk. “It used to be that the NSA squeezed all risk out of everything,” he said. Even lower-levels of sensitivity were covered by Top Secret-level crypto. “We don’t do that now—it’s levels of risk. We say we can give you this, but can ensure only this level of risk.” Partly this came about, he suggested, because the military has an inherent understanding that nothing is without risk, and is used to seeing things in terms of tradeoffs: “With the military, everything is a risk decision. If this is the communications capability I need, I’ll have to take that risk.”

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Posted on September 20, 2012 at 6:02 AM • View Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.