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Article #3Re: Gathering entropy for PRNGs on MVS
From: Michael Amling
Date: Tue, 11 Mar 2003 04:23
Date: Tue, 11 Mar 2003 04:23
27 lines
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3090 bytes
Duke Arber wrote: >>That means you're running on a virtual machine, right? There's no >>entropy at all. Well, maybe you can sample a CPU cycle counter over a >>long period or something like that. There could be some entropy there >>because of how other VM's on the same physical machine cause your >>program to have more or less cache hits and misses. > > > MVS can run as a guest O/S on IBM's VM O/S or it can run as the only O/S. > The most likely case is running as the only O/S. The STCK instruction retrieves the actual system clock whether or not MVS is running under VM. You can use the STIMER macro to request an IRB be scheduled. Code running under the IRB can inspect the register contents of the interrupted PRB (although IIRC, the IRB is postponed if an SVRB is in progress). You can step through LPA, hoping for a page fault that would make the difference between STCK values less predictable. A fair amount of CSA is fetchable, and if it isn't there's some variance to be had in the time it takes to dispatch your ESTAE routine. I don't recall offhand if the trace table in the nucleus is fetch protected. It probably is. ENQing on a global resource can get you some variance in the time it takes for the token to pass through the various channel-to-channel adapters. --Mike Amling
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X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: fd4af,4336d2c2bccbde14 X-Google-Attributes: gidfd4af,public X-Google-Thread: fed83,4336d2c2bccbde14 X-Google-Attributes: gidfed83,public X-Google-Thread: fb57f,4336d2c2bccbde14 X-Google-Attributes: gidfb57f,public X-Google-ArrivalTime: 2003-03-10 19:27:11 PST Path: arc1-ca.pugleaf.net!archiver1.google.com!news1.google.com!newsfeed.stanford.edu!cyclone.bc.net!sjc70.webusenet.com!news.webusenet.com!pd2nf1so.cg.shawcable.net!residential.shaw.ca!prodigy.com!newsmst01.news.prodigy.com!prodigy.com!postmaster.news.prodigy.com!newssrv26.news.prodigy.com.POSTED!not-for-mail Message-ID: <3E6D5722.1080101@nospam.com> From: Michael Amling <nospam@nospam.com> User-Agent: Mozilla/5.0 (Macintosh; U; PPC Mac OS X; en-US; rv:1.0.2) Gecko/20021120 Netscape/7.01 X-Accept-Language: en, en-us, en-gb, de, de-de MIME-Version: 1.0 Newsgroups: sci.crypt.random-numbers,bit.listserv.ibm-main,sci.crypt Subject: Re: Gathering entropy for PRNGs on MVS References: <b4ieak$2qn$1@slb9.atl.mindspring.net> <7xsmtvqidp.fsf@ruckus.brouhaha.com> <b4igi5$f6p$1@slb9.atl.mindspring.net> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Lines: 28 NNTP-Posting-Host: 68.23.41.46 X-Complaints-To: abuse@prodigy.net X-Trace: newssrv26.news.prodigy.com 1047356581 ST000 68.23.41.46 (Mon, 10 Mar 2003 22:23:01 CST) NNTP-Posting-Date: Mon, 10 Mar 2003 22:23:01 CST Organization: Prodigy Internet http://www.prodigy.com X-UserInfo1: FKPO@MONXJVIBPLX@ZJD]_\@VR]^@B@MCPWZKB]MPXHDUWYAKVUOPCW[ML\JXUCKVFDYZKBMSFX^OMSAFNTINTDDMVW[X\THOPXZRVOCJTUTPC\_JSBVX\KAOTBAJBVMZTYAKMNLDI_MFDSSOLXINH__FS^\WQGHGI^C@E[A_CF\AQLDQ\BTMPLDFNVUQ_VM Date: Tue, 11 Mar 2003 04:23:01 GMT