[Standards] OMEMO and Olm

Remko Tronçon remko at el-tramo.be
Sun May 28 06:15:30 UTC 2017


> eg. CMov is an operation that copies
> data if some condition is true, but without actually branching, which
> makes things a lot faster


Is this really true? You can do *a lot* of branches+memcpys for 3 loops
over all data as far as I know. I would have guessed this was a measure
against timing attacks. Where is this CMov coming from?

The reason I'm nitpicking is this: even with a single properly licensed
XEdDSA implementation in an unestablished library (or libolm), I still feel
uncomfortable depending a XEP on it. There's a certain amount of
uncertainty whether the author didn't "reuse existing bits of software" (an
expression thrown around a few times on this list recently), perhaps
infringing copyright in the process, making me as a software vendor
vulnerable to legal attacks. This is why I asked for an implementation in
an established crypto library like OpenSSL or LibSodium, where, besides
review of quality, contributors sign agreements. I would then feel safer
that the heat isn't directly on me if something is wrong copyright-wise
with the libraries i'm using.

Remko
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