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Re: [TLS] [Cfrg] 3DES diediedie

Joachim Strömbergson <joachim@secworks.se> Thu, 01 September 2016 17:57 UTC

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Date: Thu, 01 Sep 2016 19:57:23 +0200
From: Joachim Strömbergson <joachim@secworks.se>
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To: Hilarie Orman <hilarie@purplestreak.com>
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Subject: Re: [TLS] [Cfrg] 3DES diediedie
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Aloha!

Hilarie Orman wrote:
> For devices you refer to, how many AES blocks can they encrypt on a
> AA battery, assuming that the usage is to encrypt one block every 10
> minutes?

That is actually a very interesting, but hard question to answer. Will
the MCU be doing anything else in between? What kind of I/O will the
resulting block be sent over? The AES core itself can be switched off
from power on a single cycle

What I have seen is projects where one of those devices are being used
to send data at about that rate (AES-CTR encrypted) powered by a small
cell battery with a lifespan of at least 8 years. It does very little in
between though. Rough calculation gives 420k events, but each message
generated by an event is larger than a single AES block.

One thing to note is that 8-bit MCUs are commonly manufactured in older
chip processes with bigger transistors and power hungry I/Os, less power
modes than these newer ARM devices.

- -- 
Med vänlig hälsning, Yours

Joachim Strömbergson - Alltid i harmonisk svängning.
========================================================================
 Joachim Strömbergson          Secworks AB          joachim@secworks.se
========================================================================
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