[Cryptography] composing EC & RSA encryption?

[Tony Arcieri]

On Sun, Oct 25, 2015 at 5:42 AM, ianG <iang at iang.org> wrote:

> The recent "distancing" news from NSA concerning ECC and their view that
> QC is coming sooner [0] rather than later has somewhat upset things.
>
> An EC/RSA signing form is easy - just make one signature in RSA and one in
> EC, and we're done.  At least at a trivial level, this works, although I
> imagine it might be possible to do better - interesting work for a grad
> student perhaps.
>
> But what about encryption?


First, if your worry is QCs, then trying to combine ECC and RSA isn't going
to help you as they'll both be obliterated by QCs.

However, the general idea of combining multiple algorithms isn't inherently
bad. What you would *actually* want to do is combine e.g. ECC with an
as-yet-unproven quantum algorithm, like Ring-LWE (possibly not a good idea
due to patents, but let's go with it for now)

In that case, you can do a key exchange with both algorithms, and feed the
results of both into a KDF (e.g. concatenating the keys exchanged together
as KDF inputs)

This sort of scheme should be at least as strong as the strongest of the
two.

-- 
Tony Arcieri
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.metzdowd.com/pipermail/cryptography/attachments/20151025/2c38ba8b/attachment.html>