IBAA recommendation

[Robin Carey <robin.carey1@xxxxxxxxxxxxxx>]

Dear DragonFlyBSD bugs.

 

DragonFly uses Bob Jenkins' IBAA CSPRNG for /dev/random.

 

I have been doing some work on this CSPRNG, which is available from:

 

http://www.leopard.uk.com/IBAA64

 

I have two recommendations to make with regard to the IBAA CSPRNG which is used in DragonFly:

 

(1) Use my rounded up BETA=32/SHIFT=20 values as opposed to the original SHIFT=19 value in the

original IBAA CSPRNG/algorithm (details available from above URL)

 

and

 

(2) Use a 32-bit counter. This is a minor modification, which gurantees no bad states (an initial state of all zeroes

     maps back to an internal state of all zeroes after 256 iterations), and also guarantees a cycle length of at least

     2^32. Details on how to implement the counter are available from the above URL. It's a minor modification which

     has minimal performance impact.

Also, a 64-bit version of IBAA is available from the above URL. Matthew Dillon seemed to be interested in that, with

regard to the 64-bit x86-64 port of DragonFly (but I haven't heard back from him about that).

--
Sincerely,
Robin Carey