[OTR-dev] OMEMO, PFS

[Greg Troxel]

Ximin Luo <infinity0 at pwned.gg> writes:

> Hi Greg, allow me to refer you to a previous post I wrote:
>
> https://moderncrypto.org/mail-archive/messaging/2015/001877.html
>
> The TL;DR is that to achieve "forward-secrecy for in-transit messages"
> you need to have some sort of timeout mechanism, as opposed to using
> cryptographic techniques. I'm not sure if people have engineered this
> specifically into any protocols, but it would be more of an
> engineering task than a cryptography task.

That's a good point.   I think timeouts are independent of persistence,
except that without persistence you need to have a way to recover from
sooner-than-intended loss of keymat.

In the OTR world, is there a notion that implementations MUST NOT
persist keys in ways that could survive a power cycle?  (more or less -
not trying to argue RAM permanence, but more that RAM and flash are very
different points in the space)   Or is this a local option for
implementors?
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