Baud rate?

[Daniel Silverstone]

On Sat, Jul 07, 2012 at 01:02:45PM -0700, Liam D. Gray wrote:
> Let me put it this way: Full rate for USB 1.1, apparently used here,
> is 12 Megabits per second.  But a device has the option to fill any
> portion of the channel capacity, from zero to 100%.  So at what rate
> does Entropy Key send entropic bits into the 12Mbit/sec channel?  This
> determines how quickly my receive buffer will fill up after each time
> I tell Entropy Key to start sending.

The device sends at the rate it generates at.  Typically for current release
hardware I believe that's in the region of 35kSh/s.  Each packet transfers at
most 32 bytes of random data which contains 256 shannons of entropy.

Each packet is 64 characters long thanks to the encoding, packetisation, MAC,
etc (see the protocol document in the source tarball for the ekeyd program) and
as such you can expect ca. 135 packets per second at 64 bytes per packet.
Approximately 8.5 KiB/s. (70kbit/s)

> A clever suggestion.  Actually I may want to be my own
> man-in-the-middle for this application: I want my microcontroller to
> control something with the entropic bits from Entropy Key before*
> passing them on to a host computer that will log them.  (*Not after,
> and there's a reason for that.) And I want to avoid using the
> non-payload part of the stream, those parts added by the protocol for
> its own use.  I don't want to use any of the protocol's
> configuration/control bits, because they are not independently derived
> from (though I'll happily permit any pure permutation of) quantum
> random processes.  (This is for faithfulness in replicating an
> experiment whose whose results and mechanism we are very far from
> understanding.)

The protocol in the Entropy Key is designed to be resistant to such "attacks".
You'd do much better to MiM in the host between the consumer of the entropy and
wherever it reads from.  Safer and more predictable.

(I took so long answering this because I needed to discover it in a side
folder.  Please send responses to the list, not to me directly.)

D.

-- 
Daniel Silverstone                         http://www.digital-scurf.org/
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