[DragonFlyBSD - Bug #1689] IBAA recommendation

bugtracker-admin at leaf.dragonflybsd.org bugtracker-admin at leaf.dragonflybsd.org
Mon Jan 19 06:24:12 PST 2015

Issue #1689 has been updated by alexh.

We should stay away from non-reviewed work in this area. Bob Jenkins' IBAA/ISAAC implementations have been used and reviewed a fair number of times, unlike rcarey's work.

The main reason we still have IBAA around is as a sort of safety net against any potential (implementation) bugs in the new CSPRNG. As such, it sounds like a pretty bad idea to try and tweak it like this.

IMO this should be closed, but I'll leave it up to you.

Bug #1689: IBAA recommendation

* Author: robin.carey1
* Status: Feedback
* Priority: Low
* Assignee: 
* Category: Crypto
* Target version: 4.2.x
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:


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)


(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).

unnamed (1.4 KB)

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