Year: 2016
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Bitcoin is unstable without the block reward
With Miles Carlsten, Harry Kalodner, and Matt Weinberg, I have a new paper titled On the instability of Bitcoin without the block reward, which Harry will present at ACM CCS next week. The paper predicts that miner incentives will start to go haywire as Bitcoin rewards shift from block rewards to transaction fees, based on…
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Open Review leads to better books
My book manuscript, Bit by Bit: Social Research in the Digital Age, is now in Open Review. That means that while the book manuscript goes through traditional peer review, I also posted it online for a parallel Open Review. During the Open Review everyone—not just traditional peer reviewers—can read the manuscript and help make it…
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The Effect of DNS on Tor’s Anonymity
This blog post is joint work with Benjamin Greschbach, Tobias Pulls, Laura M. Roberts, and Nick Feamster. Counting almost two million daily users and 7,000 relays, the Tor network is the largest anonymity network operating today. The Tor Project is maintaining a privacy-enhanced version of the popular Firefox web browser—Tor Browser—that bounces its network traffic…
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My testimony before the House Subcommittee on IT
I was invited to testify yesterday before the U.S. House of Representatives Subcommittee on Information Technology, at a hearing entitled “Cybersecurity: Ensuring the Integrity of the Ballot Box.” My written testimony is available here. My 5-minute opening statement went as follows: My name is Andrew Appel. I am Professor of Computer Science at Princeton University. …
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Are you really anonymous online?
As you browse the internet, online advertisers track nearly every site you visit, amassing a trove of information on your habits and preferences. When you visit a news site, they might see you’re a fan of basketball, opera and mystery novels, and accordingly select ads tailored to your tastes. Advertisers use this information to create…
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Which voting machines can be hacked through the Internet?
Over 9000 jurisdictions (counties and states) in the U.S. run elections with a variety of voting machines: optical scanners for paper ballots, and direct-recording “touchscreen” machines. Which ones of them can be hacked to make them cheat, to transfer votes from one candidate to another? The answer: all of them. An attacker with physical access…
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Bitcoin’s history deserves to be better preserved
Much of Bitcoin’s development has happened in the open in a transparent manner through the mailing list and the bitcoin-dev IRC channel. The third-party website BitcoinStats maintains logs of the bitcoin-dev IRC chats. [1] This resource has proved useful is linked to by other sources such as the Bitcoin wiki. When reading a blog post…
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All the News That’s Fit to Change: Insights into a corpus of 2.5 million news headlines
[Thanks to Joel Reidenberg for encouraging this deeper dive into news headlines!] There is no guarantee that a news headline you see online today will not change tomorrow, or even in the next hour, or will even be the same headlines your neighbor sees right now. For a real-life example of the type of change…
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Improving Bitcoin’s Privacy and Scalability with TumbleBit
Last week we unveiled TumbleBit, a new anonymous payments scheme that addresses two major technical challenges faced by Bitcoin today: (1) scaling Bitcoin to meet increasing use, and (2) protecting the privacy of payments made via Bitcoin. Our proof-of-concept source code and a pre-print of the latest version of our paper were both posted online…
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Routing Detours: Can We Avoid Nation-State Surveillance?
Since 2013, Brazil has taken significant steps to build out their networking infrastructure to thwart nation-state mass surveillance. For example, the country is deploying a 3,500-mile fiber cable from Fortaleza, Brazil to Portugal; they’ve switched their government email system from Microsoft Outlook to a state-built system called Expresso; and they now have the largest IXP…