From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,ac39a12d5faf5b14 X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2002-04-24 08:40:14 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!newsfeed1.cidera.com!Cidera!cyclone.socal.rr.com!cyclone3.kc.rr.com!news3.kc.rr.com!twister.socal.rr.com.POSTED!not-for-mail Message-ID: <3CC6D1EC.FF2B4D1D@san.rr.com> From: Darren New X-Mailer: Mozilla 4.77 [en] (Windows NT 5.0; U) X-Accept-Language: en MIME-Version: 1.0 Newsgroups: comp.lang.ada Subject: Re: Grace and Maps (was Re: Development process in the Ada community) References: <3CB46975.90408@snafu.de> <3CBAFFEE.2080708@snafu.de> <4519e058.0204171036.6f0a7394@posting.google.com> <3CBDD795.4060706@snafu.de> <4519e058.0204180800.44fac012@posting.google.com> <3CBF0341.8020406@mail.com> <4519e058.0204190529.559a47ae@posting.google.com> <3CC1C6B3.6060306@telepath.com> <3CC21747.5000501@telepath.com> <4519e058.0204220534.2eb33730@posting.go <3CC48F34.5A474E0F@boeing.com> <3CC49C50.485AE213@san.rr.com> <3CC4B5C0.4D16077C@acm.org> <3CC4E9DA.E02BE0DA@san.rr.com> <7vznzukhzf.fsf@vlinux.voxelvision.no> <3CC5B161.C719C5D8@san.rr.com> <7vg01lwaku.fsf@vlinux.voxelvision.no> <3CC6B932.75C468E1@san.rr.com> <7vbsc9w367.fsf@vlinux.voxelvision.no> <3CC6CED0.C5E203F9@san.rr.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Date: Wed, 24 Apr 2002 15:39:11 GMT NNTP-Posting-Host: 66.75.151.160 X-Complaints-To: abuse@rr.com X-Trace: twister.socal.rr.com 1019662751 66.75.151.160 (Wed, 24 Apr 2002 08:39:11 PDT) NNTP-Posting-Date: Wed, 24 Apr 2002 08:39:11 PDT Organization: RoadRunner - West Xref: archiver1.google.com comp.lang.ada:23061 Date: 2002-04-24T15:39:11+00:00 List-Id: Darren New wrote: > /* Crappy pseudo-C... This should find about 2**16 collisions. */ > for (i = 0; i < 2**32; i++) { > if (burtle(i, ...) == 27) { > printf("Found one that hashes to 27: %ul\n", i); > } > } Actually, I take that back. That was dumb. It won't find nearly that many collisions, if "burtle" is returning a 32-bit integer. But the point is severalfold: 1) I *can* find collisions, regardless of the code that implements the hash, 2) Using a cryptographically secure hash with a large range is probably overkill for a basic hash library, so at least the vulnerability should be thought about, 3) if you can insert multiple records with the same key, you can wind up with a system that hashes lots of different stuff to the same value. 4) Hashes are nevertheless an extremely useful library component. -- Darren New San Diego, CA, USA (PST). Cryptokeys on demand. The 90/10 rule of toothpaste: the last 10% of the tube lasts as long as the first 90%.