The National Security Agency is bypassing encrypted Internet connections because the encryption data is all the same, researchers posited this week. It has long been believed the NSA had a way to bypass common types of encryption, but its methods haven’t been known.
“There have been rumors for years that the NSA can decrypt a significant fraction of encrypted Internet traffic,” Alex Halderman and Nadia Heninger wrote in a study Wednesday. “The key is, somewhat ironically, Diffie-Hellman key exchange, an algorithm that we and many others have advocated as a defense against mass surveillance.”
Along with twelve co-authors, Heninger and Halderman presented their research on the topic in a paper this week.
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In short, the Diffie-Hellman method uses the same data, called a “prime,” to encrypt connections. When it was created, the researchers wrote, “There seemed to be no reason why everyone couldn’t just use the same prime, and, in fact, many applications tend to use standardized or hard-coded primes.” The problem with that, they said, is that “an adversary can perform a single enormous computation to ‘crack’ a particular prime, then easily break any individual connection.”
In the past, that wasn’t considered a problem. “For the most common strength of Diffie-Hellman (1024 bits), it would cost a few hundred million dollars to build a machine,” the researchers said, and would be a feat “not seen since the Enigma cryptanalysis during World War II.”
Thanks to budget documents leaked by Edward Snowden in 2013, researchers now know that the NSA has the budget to facilitate such a project. “It shows that the agency’s budget is on the order of $10 billion a year, with over $1 billion dedicated to computer network exploitation, and several subprograms in the hundreds of millions a year,” the paper said.
As a result, 1024-bit HTTPS, SSH, and VPN connections — all common types of encryption — are vulnerable to NSA penetration. Joseph Bonneau, a postdoctoral researcher at the Applied Crypto Group at Stanford University and fellow at the Electronic Frontier Foundation who did not work on the study, said the study would serve to motivate the virtual community to change their longstanding practices.
“It’s hard to get people to upgrade until there is a smoking gun showing that things are broken,” Bonneau told the Washington Examiner. “Really we knew 1024-bit Diffie-Hellman was vulnerable a decade ago and the Internet dragged their feet on changing. Going forward we need to be more proactive,” he said.
Bonneau added that truly secure encryption in the needs to use 2048-bit keys. “It’s not simply twice as hard to break through, but many millions or billions of times harder.”
For those seeking to protect themselves, Heninger suggested several simple solutions. “For 99 percent of cases: Keep your software up to date, use a password manager, two-factor authentication, and disk encryption,” she told the Examiner. “For people writing software or managing systems, follow recommended timelines for deprecating insecure algorithms and cryptographic key sizes.”
In addition to the technical issues that programmers need to cope with as a result of the research, Heninger said there’s a practical component for people outside of the technical community should confront as well.
“In cases where maintaining an intelligence advantage is arguably causing current or future harm to broader security (with this kind of broad vulnerability, or with backdoored standards or software, or by exploiting software vulnerabilities instead of fixing them) we should be having a broader discussion in society for what the right tradeoff is,” Heninger said.
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Bonneau concurred, saying that the NSA’s mission of protecting Americans at the same time it degrades system security is “has been widely pointed out to be a dangerous combination, because it means when the NSA finds flaws it may not disclose them publicly, hoping it is the only agency that has found them.”
