IETF Draft Wants To Formalize 'Man-In-The-Middle' Decryption Of Data As It Passes Through 'Trusted Proxies'

from the you-jest dept

One of the (many) shocking revelations from the Snowden leaks is that the NSA and GCHQ use "man-in-the-middle" (MITM) attacks to impersonate Internet services like Google, to spy on encrypted communications. So you might think that nobody would want to touch this tainted technology with a barge-pole. But as Lauren Weinstein points out in an interesting post, the authors of an IETF (Internet Engineering Task Force) Internet Draft, "Explicit Trusted Proxy in HTTP/2.0," are proposing not just to use MITMs, but also to formalize their use. Here's his explanation of the rationale:

one of the "problems" with SSL/TLS connections (e.g. https:) -- from the standpoint of the dominant carriers anyway -- is that the connections are, well, fairly secure from snooping in transit (assuming your implementation is correct ... right?)

But some carriers would really like to be able to see that data in the clear -- unencrypted. This would allow them to do fancy caching (essentially, saving copies of data at intermediate points) and introduce other "efficiencies" that they can't do when your data is encrypted from your client to the desired servers (or from servers to client).
The "solution" to that problem is what the authors of the IETF draft -- all of whom hail from AT&T or Ericsson -- call "trusted proxies." Basically, users give permission for their data to be decrypted by an intermediate site that they trust, which would then be allowed to do stuff to it before re-encrypting it and passing it along to its original destination. The eagle-eyed among you may have spotted one or two problems with this approach; as Weinstein says:
Of course, the authors of this proposal are not oblivious to the fact that there might be a bit of resistance to this "Trust us" concept. So, for example, the proposal includes the assumption of mechanisms for users to opt-in or opt-out of these "trusted proxy" schemes.

But it's easy to be extremely dubious about what this would mean in the real world. Can we really be assured that a carrier going through all the trouble of setting up these proxies would always be willing to serve users who refuse to agree to the proxies being used, and allow those users to completely bypass the proxies? Count me as skeptical.

And the assumption that users can even be expected to make truly informed decisions about this seems highly problematic from the git-go. We might be forgiven for suspecting that the carriers are banking on the vast majority of users simply accepting the "Trust us -- we're your friendly man-in-the-middle" default, and not even thinking about the reality that their data is being decrypted in transit by third parties.
And there's another major issue. If there's one thing we've learned from Snowden it's that the NSA and GCHQ have no compunction about breaking into anyone's system. If decrypted versions of data transmissions were available on these "trusted proxies," they would no doubt become prime targets for this kind of attention. Introducing another weak link into the transmission chain would leave Internet users even more exposed to surveillance than before. Before Snowden's leaks, 'man-in-the-middle' decryption of the kind being proposed would have seemed a pretty bad idea; in the wake of them, it is just plain crazy.

Follow me @glynmoody on Twitter or identi.ca, and +glynmoody on Google+

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Filed Under: encryption, ietf, man-in-the-middle, security, ssl


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  1. identicon
    Anonymous Coward, 27 Feb 2014 @ 7:47am

    how long until somebody comes up with a VPN system that uses a second encryption of a different kind within the SSL encrypted packets?

    I would propose to call it the "fuck you protocol"

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