This paper investigates the security of Diffie-Hellman key exchange as used in popular Internet protocols and find it to be less secure than widely believed. First, they present Logjam, a novel flaw in TLS that lets a man-in-the-middle downgrade connections to "export-grade" Diffie-Hellman. To carry out this attack, the researchers implement the number field sieve discrete log algorithm. After a week-long precomputation for a specified 512-bit group, they can compute arbitrary discrete logs in that group in about a minute. They found that 82% of vulnerable servers use a single 512-bit group, allowing them to compromise connections to 7% of Alexa Top Million HTTPS sites. They go on to consider Diffie-Hellman with 768- and 1024-bit groups. They estimate that even in the 1024-bit case, the computations are plausible given nation-state resources. A small number of fixed or standardized groups are used by millions of servers; performing precomputation for a single 1024-bit group would allow passive eavesdropping on 18% of popular HTTPS sites, and a second group would allow decryption of traffic to 66% of IPsec VPNs and 26% of SSH servers. A close reading of published NSA leaks shows that the agency's attacks on VPNs are consistent with having achieved such a break. They conclude that moving to stronger key exchange methods should be a priority for the Internet community.
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Whitepaper called Attacking the Washington, D.C. Internet Voting System. In 2010, Washington, D.C. developed an Internet voting pilot project that was intended to allow overseas absentee voters to cast their ballots using a website. The authors of this paper participated in a challenge to break the security of the system and in doing so, elected Bender from Futurama to the school board.
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