Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263016AbTHVE3c (ORCPT ); Fri, 22 Aug 2003 00:29:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263017AbTHVE3c (ORCPT ); Fri, 22 Aug 2003 00:29:32 -0400 Received: from abraham.CS.Berkeley.EDU ([128.32.37.170]:53000 "EHLO abraham.cs.berkeley.edu") by vger.kernel.org with ESMTP id S263016AbTHVE3b (ORCPT ); Fri, 22 Aug 2003 00:29:31 -0400 To: linux-kernel@vger.kernel.org Path: not-for-mail From: daw@mozart.cs.berkeley.edu (David Wagner) Newsgroups: isaac.lists.linux-kernel Subject: Re: [RFC][PATCH] Make cryptoapi non-optional? Date: Fri, 22 Aug 2003 04:28:39 +0000 (UTC) Organization: University of California, Berkeley Distribution: isaac Message-ID: References: <20030818004313.T3708@schatzie.adilger.int> NNTP-Posting-Host: mozart.cs.berkeley.edu X-Trace: abraham.cs.berkeley.edu 1061526519 2529 128.32.153.211 (22 Aug 2003 04:28:39 GMT) X-Complaints-To: usenet@abraham.cs.berkeley.edu NNTP-Posting-Date: Fri, 22 Aug 2003 04:28:39 +0000 (UTC) X-Newsreader: trn 4.0-test74 (May 26, 2000) Originator: daw@mozart.cs.berkeley.edu (David Wagner) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1072 Lines: 18 David Lang wrote: >On Mon, 18 Aug 2003, Andreas Dilger wrote: >> It wasn't even vanishingly small... We had a problem in our code where >> two readers got the same 64-bit value calling get_random_bytes(), and >> we were depending on this 64-bit value being unique. This problem was >> fixed by putting a spinlock around the call to get_random_bytes(). > >if the number is truely random then there should be a (small but finite) >chance that any two reads will return the same data. counting on a random >number to be unique is not a good idea. Have you ever worked out how small a number 2^-64 is? You might be surprised. For most practical purposes, 2^-64 is effectively zero. If you see a 64-bit values repeat twice in a row when querying a cryptographic pseudorandom generator, the crypto-PRNG is almost surely broken. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/