From owner-freebsd-current Sun Aug 27 9:57:58 2000 Delivered-To: freebsd-current@freebsd.org Received: from cypherpunks.ai (cypherpunks.ai [209.88.68.47]) by hub.freebsd.org (Postfix) with ESMTP id 16FD037B422; Sun, 27 Aug 2000 09:57:56 -0700 (PDT) Received: from vangelderen.org (grolsch.ai [209.88.68.214]) by cypherpunks.ai (Postfix) with ESMTP id CA8074D; Sun, 27 Aug 2000 12:57:54 -0400 (AST) Message-ID: <39A94892.EB61FC4A@vangelderen.org> Date: Sun, 27 Aug 2000 12:57:54 -0400 From: "Jeroen C. van Gelderen" X-Mailer: Mozilla 4.73 [en] (X11; I; Linux 2.2.12 i386) X-Accept-Language: en MIME-Version: 1.0 To: Mark Murray Cc: Adam Back , current@FreeBSD.ORG, kris@FreeBSD.ORG Subject: Re: yarrow & /dev/random References: <200008262349.SAA06044@cypherspace.org> <200008270735.e7R7ZXp28310@grimreaper.grondar.za> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Mark Murray wrote: [...] > Again, I'm not so sure; Yarrow goes to great trouble to protect its > internal state; by blocking, I have this very nasty suspicion that > this carefully guarded state is being disclosed. The moment you block, > you are confiding in the fact that you have no updating entropy, and > as a result /dev/urandom gan be attacked to get the internal state. You would normally assume that an attacker knows when you are not adding in entropy. In Yarrow, the assumption is that the internal state is (sufficiently) protected by both a hash and the blockcipher so blocking will not affect Yarrow's security properties AFAICS. Yes, /dev/urandom can be attacked at the point of blocking but given robust primitives the complexity is still 2^(sizeof(hash)) which is exactly the complexity Yarrow claims to provide. This is completely independent of any knowledge of reseed timings (or lack thereof). Cheers, Jeroen -- Jeroen C. van Gelderen o _ _ _ jeroen@vangelderen.org _o /\_ _ \\o (_)\__/o (_) _< \_ _>(_) (_)/<_ \_| \ _|/' \/ (_)>(_) (_) (_) (_) (_)' _\o_ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message