[tor-dev] Attentive Otter: Analysis of xmpp-client

Mike Perry mikeperry at torproject.org
Tue Oct 8 23:49:51 UTC 2013

Jurre van Bergen:
> *OTR*
> OTR support comes from the Go crypto package:
> https://code.google.com/p/go.crypto/
> This library only has support for OTRv2 and not the latest OTRv3 
> specification. If we want to be resistant to several attacks[1]  on the
> OTR protocol, we need to reimplement the OTR protocol and update it to
> the latest version or, we use Cgo, which binds into libotr. (Open
> questions: OTR by default?, )
> [1]
> http://citeseerx.ist.psu.edu/viewdoc/download?doi=

According to agl:
"The DH and DSA code uses Go's math/big library, which isn't constant

He said these non-constant time Go primitives are used by OTR, and will
be used by TLS if they are specified by the negotiated cipher suite.

So xmpp-client's OTR and TLS support would definitely need to be
rewritten to call out to a native code implementation or rewritten to
use new constant time Go primitives, independent of OTRv2 vs OTRv3.

Mike Perry
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