[zeromq-dev] Encryption (OpenSSL/TLS)

[Steve Atkins]

On Sep 30, 2010, at 4:33 PM, Blair Bethwaite wrote:

> Hi list,
> 
> We're experimenting with zmq at the moment and I've been thinking a
> little about this general issue too...
> 
> On 1 October 2010 05:05, John Flanagan <flanagan.ffs at gmail.com> wrote:
>> There are three overall approaches:
>> 
>> 1) VPN level encryption, handled UNDER zmq.
>> 2) SSL level encryption, handled BY zmq
>> 3) message level encryption, handled ON TOP OF zmq.
> 
> Succinct summary. I'd like to add a couple of talking points:
> Option (1) is clearly the most robust solution, however _deploying_ it
> in the wild is not so easy. In our use case we can only expect to have
> administrative access to one box in a large connected system running
> over heterogeneous systems. If anyone knows of a good way to create a
> static-linked binary including transparent VPN under zmq we'd love to
> hear about it.
> Option (3) should be considered weak. Even assuming key-negotiation
> etc. can be handled out-of-band easily, this approach is still open to
> man-in-the-middle and replay attacks which could break or cause
> serious disruption to the system.

Option 3 needn't be weak. It can use cryptography as strong as that
in ssl, or stronger, and can certainly be made immune to man in the
middle or replay attacks. It can all be done in-band, though it
needs PKI of some sort unless you have a shared secret.

I'm looking at doing it this way for an app I'm working on, based on
a shared secret between the two peers, and it doesn't look too painful
to do securely (PAKE, basically). I'm only concerned about protecting
payloads - traffic patterns aren't something I need to obscure.

It does require a lot more work than options 1 or 2, though, and
there's a lot more potential for making a bad crypto mistake in
there.

Cheers,
  Steve