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Security researchers have banged another nail into the coffin of the ageing RC4 encryption algorithm. The latest password recovery attacks against RC4 in TLS by Christina Garman of Johns Hopkins University, Prof. Kenny Paterson and research student Thyla van der Merwe (both of Royal Holloway, University of London) show that attacks against the scheme are getting better and easier so RC4 "needs to die", as the researchers themselves put it. The continued use of RC4 in TLS is "increasingly indefensible", the researchers conclude in an abstract of their work. The research - which also involved the development of "proof of concept" implementations of the attacks against the BasicAuth and IMAP protocols – is explained in full in a paper here (PDF, 34 pages). Independent researchers agree that RC4 needs to be pensioned off even though some question whether the attack developed by is a practical concern. "RC4 must die. Despite, not because of, attacks like the one described here which is extremely impractical," said Martijn Grooten, editor of Virus Bulletin and occasional security researcher. Caveats about whether or not attacks could be economically pulled off aside, there's little or no disagreement about the direction of travel, which is that the cipher ought to be consigned straight towards the cyber equivalent of Boot Hill cemetery. The only reason it's still around is that websites are reluctant to drop support even for obsolete technology. RC4, developed in 1987, is a popular stream cipher that's often used in HTTPS connections to protect sensitive network traffic from eavesdroppers, among other uses. Potential attacks have been documented for years but they are now decreasing in complexity to the point where using the cipher is risky even before considering the implication of the revelations from NSA whistleblower Edward Snowden. Leaks from Snowden suggested that US and UK spies have developed "groundbreaking cryptanalysis capabilities", which ultimately allow the intelligence agencies to break RC4 encryption. Distrust of the cipher is spreading. Microsoft urged Windows developers to ditch the RC4 encryption algorithm and pick something stronger back in November 2013. Cisco also told its customers to "avoid" the cipher around the same time. The IETF moved towards killing off the venerable-but-vulnerable RC4 cipher with a proposal that net-standard clients and servers need to quit using RC4 in Transport Layer Security (TLS) that surfaced in December 2014. Source
After rolling out free SSL for its users last fall, CloudFlare has deployed a new level of encryption on its service that hardens and speeds up the user experience, especially when accessing domains via mobile browsers. The form of encryption, a relatively new transport layer cipher suite known as ChaCha20-Poly1305, has largely been used by Google until now. But as of yesterday, it is being used on 10 percent of CloudFlare’s HTTPS connections with more to follow. CloudFlare’s Nick Sullivan, who described the move on the company’s blog yesterday, called the cipher fast, useful and its security level “more than sufficient” for HTTPS. The algorithm is based on a combination of two other ciphers, ChaCha20 and Poly1305 MAC, both crafted by cryptographer Daniel Bernstein in 2008 and 2005 respectively. After being batted around for a bit, it surfaced in Chrome 31 in November 2013. Sullivan points out that the cipher, when paired with TLS, should excel at bridging the gap between having secure encryption on mobile browsers and APIs. While the cipher will fill that void, it also improves upon two other alternatives, RC4, which of course has its many foibles, and AES-GCM, which can cost a fortune depending on the way its implemented. It also helps that ChaCha20-Poly1305 is three times faster than AES-128-GCM on mobile services – the cipher provides 256 bits of security over GCM’s 128 – something that should reduce the strain of batteries on mobile devices. “Spending less time on decryption means faster page rendering and better battery life,” Sullivan wrote. The content delivery network explains that the change is partly fueled by the rest of the web’s fervent push towards HTTPS but that the move could also be seen as a foreshadowing of the cipher’s future widespread adoption. Sullivan acknowledges that Mozilla is planning on adding support for it in Firefox and that at the very least, using the cipher is a good fallback in case someone digs up a bug in AES-GCM, the algorithm primarily being used right now, in the near future. Source