Re: [PATCH 5/7] random: replace non-blocking pool with a Chacha20-based CRNG
From: Theodore Ts'o <tytso@mit.edu>
Date: 2016-06-20 23:49:32
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On Mon, Jun 20, 2016 at 05:49:17PM +0200, Stephan Mueller wrote:
Is speed everything we should care about? What about: - offloading of crypto operation from the CPU
In practice CPU offland is not helpful, and in fact, in most cases is harmful, when one is only encrypting a tiny amount of data. That's because the cost of setup and teardown, not to mention key scheduling, dominate. This is less of the case in the case of the SIMD / AVX optimizations --- but that's because these are CPU instructions, and there really isn't any CPU offloading going on.
- potentially additional security features a hardware cipher may provide like cache coloring attack resistance?
Um.... have you even taken a *look* at how ChaCha20 is implemented? *What* cache coloring attack is possible at all, period? Hint: where are the lookup tables? Where are the data-dependent memory accesses in the ChaCha20 core? - Ted