Real world data on TLS power consumption on mobile devices

For those interested:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6806263/

A quick summary, focussing on stuff relevant for TLS 1.3 or TLS 1.2
limited to TLS 1.3 ciphersuites: on tested Samsung and Xioami phones,
ChaCha20-Poly1305 is both faster and consumes less battery than AES in
GCM mode - and it's not a small difference, either.

This will not necessarily generalise to PCs with modern Intel CPUs in
them, which can have dedicated hardware instructions for AES.  But on
phones, tablets, RaspberryPi's etc. it is very likely the case that
prefering ChaCha20-Poly1305 over AES will make Gemini faster and
greener.

TLS allows both the server and client to express a preference for
ciphersuites, and IIRC it's up to the server to decide whether its
preferences or the client's have the final say.  It seems to me that
servers running on VPSes, or otherwise in scenarios where they have
reliable and abundant power, ought to defer to the client's preferences
(at least by default), that mobile clients ought to explicitly prefer
ChaCha20-Poly1305 over AES, and that non-mobile clients ought to allow
users to configure this preference for themselves.  People using RPis,
older PCs without hardware AES support, etc. can then configure a
ChaCha20-Poly1305 preference and things will be faster for them.  Maybe
not noticably faster to the naked eye, but faster.

Cheers,
Solderpunk

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