Re: monitoring entropy
H. Peter Anvin (hpa@transmeta.com)
Tue, 14 Oct 1997 14:55:22 -0700 (PDT)
>
> i rather take 'entropy' as an ordinary resource, ie. a user can get it,
> root can get more, what one user gets is the property of that user, etc.
> This way the picture is extremely clear: root has reserved entropy, libc
> caches 'hard entropy', and provides infinit (weak, nonblocking) entropy
> for applications that are not security-critical. Such 'mixing' is then
> done on per-process basis.
>
This is, however, much more wasteful of true enthropy.
>
> if you read urandom in a tight loop, you drain the pool completely, and
> make the output extremely predictable ... eg TCP sequece number guessing.
>
> wether this view is correct ... dunno.
>
I think that can be worked around, but I'm not sure. Of course there
is always the ability to chmod 600 /dev/urandom, or chmod 600
/dev/random for that matter.
-hpa