rngd read error

[stan]

On Tue, 30 Jun 2015 01:11:27 +0200
Timothy Murphy <gayleard at eircom.net> wrote:

> Thanks very much.
> This gave me the info
>   Error reading from TPM, no entropy gathered
> It seems that my Thinkpad T510 has a TPM chip,
> which I probably could turn on in some way.
> 
> However, for the moment I've just run
>   sudo systemctl disable rngd

Thanks for reporting this.  I had no idea it was happening.  I'm using
audio-entropyd to augment rngd, and it still is working, so I'm not
cryptographically compromised.  This is serious, because it's like
leaving the door unlocked on your house, when every other house on the
block has been burgled.

I've been thinking about purchasing a usb entropy generator, perhaps
this is the spur to actually do so.  I think they feed directly into
the entropy pool like audio-entropyd, bypassing rngd, but I'm not sure.

There are lots of them.
https://en.wikipedia.org/wiki/Comparison_of_hardware_random_number_generators

I like this pure digital model, anyone have experience with it?
http://kidekin.nimp.co.uk/trng/kidekin_trng_user_manual.html

They all seem pretty pricey, except for 
http://kidekin.nimp.co.uk/trng/kidekin_trng_user_manual.html
These can be purchased on Ebay for less than $10.  They don't seem as
robust to me.  Has anyone used this as an RNG solution?