[cryptography] Extended Random is extended to whom, exactly?

Stephen Farrell stephen.farrell at cs.tcd.ie
Mon Mar 31 13:45:31 EDT 2014

There's a thread on the TLS list about this. [1] Essentially
there were proposals in Internet drafts to add more randomness
to the TLS exchange which the paper says (and it looks
reasonable at first glance) would have made it much easier to
exploit a known dual-ec backdoor. None of those drafts were
adopted and none became an RFC or got deployed. (Thankfully,
I guess;-)

The paper [2] also has more about exploiting dual-ec if you
know a backdoor that I've not yet read really.


[1] http://www.ietf.org/mail-archive/web/tls/current/msg11727.html
[2] http://dualec.org/

On 03/31/2014 06:36 PM, ianG wrote:
> http://www.reuters.com/article/2014/03/31/us-usa-security-nsa-rsa-idUSBREA2U0TY20140331
> (Reuters) - Security industry pioneer RSA adopted not just one but two
> encryption tools developed by the U.S. National Security Agency, greatly
> increasing the spy agency's ability to eavesdrop on some Internet
> communications, according to a team of academic researchers.
> ...
> A group of professors from Johns Hopkins, the University of Wisconsin,
> the University of Illinois and elsewhere now say they have discovered
> that a second NSA tool exacerbated the RSA software's vulnerability.
> The professors found that the tool, known as the "Extended Random"
> extension for secure websites, could help crack a version of RSA's Dual
> Elliptic Curve software tens of thousands of times faster, according to
> an advance copy of their research shared with Reuters.
> ...
> In a Pentagon-funded paper in 2008, the Extended Random protocol was
> touted as a way to boost the randomness of the numbers generated by the
> Dual Elliptic Curve.
> ...
> But members of the academic team said they saw little improvement, while
> the extra data transmitted by Extended Random before a secure connection
> begins made predicting the following secure numbers dramatically easier.
> "Adding it doesn't seem to provide any security benefits that we can
> figure out," said one of the authors of the study, Thomas Ristenpart of
> the University of Wisconsin.
> Johns Hopkins Professor Matthew Green said it was hard to take the
> official explanation for Extended Random at face value, especially since
> it appeared soon after Dual Elliptic Curve's acceptance as a U.S. standard.
> "If using Dual Elliptic Curve is like playing with matches, then adding
> Extended Random is like dousing yourself with gasoline," Green said.
> The NSA played a significant role in the origins of Extended Random. The
> authors of the 2008 paper on the protocol were Margaret Salter,
> technical director of the NSA's defensive Information Assurance
> Directorate, and an outside expert named Eric Rescorla.
> ...
> END of snippets, mostly to try and figure out what this protocol is
> before casting judgement.  Anyone got an idea?
> iang
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