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The new movie Safe House features the song “No Church in the Wild,” by Kanye West, which includes this verse:
I live by you, desire
I stand by you, walk through the fire
Your love is my scripture
Let me into your encryption
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.
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.
A U.S. federal judge has ordered a defendant to decrypt her laptop.
EDITED TO ADD (2/14): The ruling. And a good analysis.
It’s a policy debate that’s been going on since the crypto wars of the early 1990s. The FBI, NSA, and other agencies continue to claim they’re losing their ability to engage in surveillance: that it’s “going dark.” Whether the cause of the problem is encrypted e-mail, digital telephony, or Skype, the bad guys use it to communicate, so we need to pass laws like CALEA to force these services to be made insecure, so that the government can eavesdrop.
The counter-argument is the “Golden Age of Surveillance”—that the massive increase of online data and Internet communications systems gives the government a far greater ability to eavesdrop on our lives. They can get your e-mail from Google, regardless of whether you use encryption. They can install an eavesdropping program on your computer, regardless of whether you use Skype. They can monitor your Facebook conversations, and learn thing that just weren’t online a decade ago. Today we all carry devices that tract our locations 24/7: our cell phones.
In this essay, CDT fellows (and law professors) challenge the “going dark” metaphor and make the case for “the golden age of surveillance.” Yes, wiretapping is harder; but so many other types of surveillance are easier.
A simple test can help the reader decide between the “going dark” and “golden age of surveillance” hypotheses. Suppose the agencies had a choice of a 1990-era package or a 2011-era package. The first package would include the wiretap authorities as they existed pre-encryption, but would lack the new techniques for location tracking, confederate identification, access to multiple databases, and data mining. The second package would match current capabilities: some encryption-related obstacles, but increased use of wiretaps, as well as the capabilities for location tracking, confederate tracking and data mining. The second package is clearly superior—the new surveillance tools assist a vast range of investigations, whereas wiretaps apply only to a small subset of key investigations. The new tools are used far more frequently and provide granular data to assist investigators.
A longer and more detailed version of the same argument can be found in “Encryption and Globalization,” forthcoming in the Columbia Science and Technology Law Review.
In a related story, there’s a relatively new WikiLeaks data dump of documents related to government surveillance products.
In 1997, I wrote about something called a chosen-protocol attack, where an attacker can use one protocol to break another. Here’s an example of the same thing in the real world: two different parking garages that mask different digits of credit cards on their receipts. Find two from the same car, and you can reconstruct the entire number.
I have to admit this puzzles me, because I thought there was a standard for masking credit card numbers. I only ever see all digits except the final four masked.
Sidebar photo of Bruce Schneier by Joe MacInnis.