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Duplicate GuidJay,
You probably have better odds at winning the lottery. Seriously. What is your concern? -- Show quoteHide quote- Nicholas Paldino [.NET/C# MVP] - mvp@spam.guard.caspershouse.com "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message news:OHlTnMsZFHA.2288@TK2MSFTNGP14.phx.gbl... > Does anybody know the odds of generating a duplicate guid? > > -- > Jay Douglas > http://jaydouglas.com > > > Just wondering ... just candy for the mind.
I've heard someone say the odds are about the same as winning the Texas lottery 32 times. I was just hoping a formula or a number. I slept though statistics, so I can't come up with a good answer. Show quoteHide quote "Nicholas Paldino [.NET/C# MVP]" <mvp@spam.guard.caspershouse.com> wrote in message news:O8jeiQsZFHA.2288@TK2MSFTNGP14.phx.gbl... > Jay, > > You probably have better odds at winning the lottery. Seriously. > > What is your concern? > > -- > - Nicholas Paldino [.NET/C# MVP] > - mvp@spam.guard.caspershouse.com > > "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message > news:OHlTnMsZFHA.2288@TK2MSFTNGP14.phx.gbl... >> Does anybody know the odds of generating a duplicate guid? >> >> -- >> Jay Douglas >> http://jaydouglas.com >> >> >> > > Jay,
I remember reading something that said you had to generate 1000 new GUIDs per second for the next 5000 years in order to come across a duplicate (or something like that). I wouldn't worry =) -- Show quoteHide quote- Nicholas Paldino [.NET/C# MVP] - mvp@spam.guard.caspershouse.com "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message news:Om6pzWsZFHA.3876@TK2MSFTNGP12.phx.gbl... > Just wondering ... just candy for the mind. > > I've heard someone say the odds are about the same as winning the Texas > lottery 32 times. > > I was just hoping a formula or a number. > > I slept though statistics, so I can't come up with a good answer. > > -- > Jay Douglas > http://jaydouglas.com > > > "Nicholas Paldino [.NET/C# MVP]" <mvp@spam.guard.caspershouse.com> wrote > in message news:O8jeiQsZFHA.2288@TK2MSFTNGP14.phx.gbl... >> Jay, >> >> You probably have better odds at winning the lottery. Seriously. >> >> What is your concern? >> >> -- >> - Nicholas Paldino [.NET/C# MVP] >> - mvp@spam.guard.caspershouse.com >> >> "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message >> news:OHlTnMsZFHA.2288@TK2MSFTNGP14.phx.gbl... >>> Does anybody know the odds of generating a duplicate guid? >>> >>> -- >>> Jay Douglas >>> http://jaydouglas.com >>> >>> >>> >> >> > > Nicholas Paldino [.NET/C# MVP] wrote:
> Jay, Which would be the same as 1 million new GUIDs per second for the next 5 years, > > I remember reading something that said you had to generate 1000 new > GUIDs per second for the next 5000 years in order to come across a duplicate > (or something like that). > > I wouldn't worry =) > > or 1 billion per second for the next couple of days, would it not? If it's that easy, I would worry. -rick- Probably not possible. Two computers would have to be built as exactly the
same time, have the same MAC address (normally impossible), and generate a GUID at exactly the same time. (Actually, I vaguely remember that MS doesn't use the MAC address anymore, but I may be mistaken.) -- Show quoteHide quoteJonathan Allen "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message news:OHlTnMsZFHA.2288@TK2MSFTNGP14.phx.gbl... > Does anybody know the odds of generating a duplicate guid? > > -- > Jay Douglas > http://jaydouglas.com > > > Okay math wizards, a Guid is 32 hexidecimal digits.
Each digit can be A-F or 0-9 which amounts to 16. so, 32 possiblities of 16 characters .. what's the formula Show quoteHide quote "Jonathan Allen" <x@x.x> wrote in message news:%23pL8IXsZFHA.2520@TK2MSFTNGP09.phx.gbl... > Probably not possible. Two computers would have to be built as exactly the > same time, have the same MAC address (normally impossible), and generate a > GUID at exactly the same time. (Actually, I vaguely remember that MS > doesn't use the MAC address anymore, but I may be mistaken.) > > -- > Jonathan Allen > > > "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message > news:OHlTnMsZFHA.2288@TK2MSFTNGP14.phx.gbl... >> Does anybody know the odds of generating a duplicate guid? >> >> -- >> Jay Douglas >> http://jaydouglas.com >> >> >> > > Let's make this simpler. It's a 128 bit number, which means that there
are 2^128 possibilities. That turns out to be: 3.4028236692093846346337460743177e+38 That's a large number. -- Show quoteHide quote- Nicholas Paldino [.NET/C# MVP] - mvp@spam.guard.caspershouse.com "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message news:Ouff6nsZFHA.2664@TK2MSFTNGP15.phx.gbl... > Okay math wizards, a Guid is 32 hexidecimal digits. > > Each digit can be A-F or 0-9 which amounts to 16. > > so, 32 possiblities of 16 characters .. what's the formula > > > > -- > Jay Douglas > http://jaydouglas.com > > > "Jonathan Allen" <x@x.x> wrote in message > news:%23pL8IXsZFHA.2520@TK2MSFTNGP09.phx.gbl... >> Probably not possible. Two computers would have to be built as exactly >> the same time, have the same MAC address (normally impossible), and >> generate a GUID at exactly the same time. (Actually, I vaguely remember >> that MS doesn't use the MAC address anymore, but I may be mistaken.) >> >> -- >> Jonathan Allen >> >> >> "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message >> news:OHlTnMsZFHA.2288@TK2MSFTNGP14.phx.gbl... >>> Does anybody know the odds of generating a duplicate guid? >>> >>> -- >>> Jay Douglas >>> http://jaydouglas.com >>> >>> >>> >> >> > > Nicholas,
Well put! Taught me a little about coming up with the possibilities using the bit^2 deal too. Thanks again. Show quoteHide quote "Nicholas Paldino [.NET/C# MVP]" <mvp@spam.guard.caspershouse.com> wrote in message news:OZwCGssZFHA.3132@TK2MSFTNGP09.phx.gbl... > Let's make this simpler. It's a 128 bit number, which means that there > are 2^128 possibilities. That turns out to be: > > 3.4028236692093846346337460743177e+38 > > That's a large number. > > > -- > - Nicholas Paldino [.NET/C# MVP] > - mvp@spam.guard.caspershouse.com > > "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message > news:Ouff6nsZFHA.2664@TK2MSFTNGP15.phx.gbl... >> Okay math wizards, a Guid is 32 hexidecimal digits. >> >> Each digit can be A-F or 0-9 which amounts to 16. >> >> so, 32 possiblities of 16 characters .. what's the formula >> >> >> >> -- >> Jay Douglas >> http://jaydouglas.com >> >> >> "Jonathan Allen" <x@x.x> wrote in message >> news:%23pL8IXsZFHA.2520@TK2MSFTNGP09.phx.gbl... >>> Probably not possible. Two computers would have to be built as exactly >>> the same time, have the same MAC address (normally impossible), and >>> generate a GUID at exactly the same time. (Actually, I vaguely remember >>> that MS doesn't use the MAC address anymore, but I may be mistaken.) >>> >>> -- >>> Jonathan Allen >>> >>> >>> "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message >>> news:OHlTnMsZFHA.2288@TK2MSFTNGP14.phx.gbl... >>>> Does anybody know the odds of generating a duplicate guid? >>>> >>>> -- >>>> Jay Douglas >>>> http://jaydouglas.com >>>> >>>> >>>> >>> >>> >> >> > > I thought its a combination of MAC address and current clock
tick(Year-Month-Day-HH:MM:SS:millisecond). So, probablility of getting a duplicate is virtually 0. Show quoteHide quote "Jonathan Allen" wrote: > Probably not possible. Two computers would have to be built as exactly the > same time, have the same MAC address (normally impossible), and generate a > GUID at exactly the same time. (Actually, I vaguely remember that MS doesn't > use the MAC address anymore, but I may be mistaken.) > > -- > Jonathan Allen > > > "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message > news:OHlTnMsZFHA.2288@TK2MSFTNGP14.phx.gbl... > > Does anybody know the odds of generating a duplicate guid? > > > > -- > > Jay Douglas > > http://jaydouglas.com > > > > > > > > > but you can never be sure. since the guid is generated using a hashfunction
of the values you mentioned, errors in the implemention of the hashfunction can lead to duplicated guids. Show quoteHide quote "Ravi Shankar" <Ravi Shan***@discussions.microsoft.com> schrieb im Newsbeitrag news:DFFD3CA5-528A-4219-8A25-075FDB7C8B26@microsoft.com... > I thought its a combination of MAC address and current clock > tick(Year-Month-Day-HH:MM:SS:millisecond). So, probablility of getting a > duplicate is virtually 0. > > > "Jonathan Allen" wrote: > > > Probably not possible. Two computers would have to be built as exactly the > > same time, have the same MAC address (normally impossible), and generate a > > GUID at exactly the same time. (Actually, I vaguely remember that MS doesn't > > use the MAC address anymore, but I may be mistaken.) > > > > -- > > Jonathan Allen > > > > > > "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message > > news:OHlTnMsZFHA.2288@TK2MSFTNGP14.phx.gbl... > > > Does anybody know the odds of generating a duplicate guid? > > > > > > -- > > > Jay Douglas > > > http://jaydouglas.com > > > > > > > > > > > > > > > I thought that MS stopped using the MAC address to create the guids since
the cheaper NIC cards were producing duplicate MAC addresses at an alarming rate. Show quoteHide quote "cody" <deutron***@gmx.de> wrote in message news:eBqI6a4ZFHA.3808@TK2MSFTNGP09.phx.gbl... > but you can never be sure. since the guid is generated using a > hashfunction > of the values you mentioned, errors in the implemention of the > hashfunction > can lead to duplicated guids. > > "Ravi Shankar" <Ravi Shan***@discussions.microsoft.com> schrieb im > Newsbeitrag news:DFFD3CA5-528A-4219-8A25-075FDB7C8B26@microsoft.com... >> I thought its a combination of MAC address and current clock >> tick(Year-Month-Day-HH:MM:SS:millisecond). So, probablility of getting a >> duplicate is virtually 0. >> >> >> "Jonathan Allen" wrote: >> >> > Probably not possible. Two computers would have to be built as exactly > the >> > same time, have the same MAC address (normally impossible), and >> > generate > a >> > GUID at exactly the same time. (Actually, I vaguely remember that MS > doesn't >> > use the MAC address anymore, but I may be mistaken.) >> > >> > -- >> > Jonathan Allen >> > >> > >> > "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message >> > news:OHlTnMsZFHA.2288@TK2MSFTNGP14.phx.gbl... >> > > Does anybody know the odds of generating a duplicate guid? >> > > >> > > -- >> > > Jay Douglas >> > > http://jaydouglas.com >> > > >> > > >> > > >> > >> > >> > > > "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message That's right, microsoft doesn't use the DCE algorithm on NT based systems news:%23gGYnk4ZFHA.4068@TK2MSFTNGP10.phx.gbl... >I thought that MS stopped using the MAC address to create the guids since >the cheaper NIC cards were producing duplicate MAC addresses at an alarming >rate. > > -- > Jay Douglas > http://jaydouglas.com > > (since NT4 SP4), but the reason was a bit of "privacy paranoia", people didn't like to give away their MAC addresses through a GUID. Willy. Willy Denoyette [MVP] wrote:
Show quoteHide quote > "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message Is the algorithm MS uses to create a GUID published somewhere?> news:%23gGYnk4ZFHA.4068@TK2MSFTNGP10.phx.gbl... > >>I thought that MS stopped using the MAC address to create the guids since >>the cheaper NIC cards were producing duplicate MAC addresses at an alarming >>rate. >> >>-- >>Jay Douglas >>http://jaydouglas.com >> >> > > > That's right, microsoft doesn't use the DCE algorithm on NT based systems > (since NT4 SP4), but the reason was a bit of "privacy paranoia", people > didn't like to give away their MAC addresses through a GUID. > > Willy. > > -Mark
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"Mark Rance" <spamFree@nomail.com> wrote in message ..NET uses RNGCryptoServiceProvider which is a wrapper over the cryptographicnews:z7adncvMfbBIbzzfRVn-3A@pcisys.net... > Willy Denoyette [MVP] wrote: >> "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message >> news:%23gGYnk4ZFHA.4068@TK2MSFTNGP10.phx.gbl... >> >>>I thought that MS stopped using the MAC address to create the guids since >>>the cheaper NIC cards were producing duplicate MAC addresses at an >>>alarming rate. >>> >>>-- >>>Jay Douglas >>>http://jaydouglas.com >>> >>> >> >> >> That's right, microsoft doesn't use the DCE algorithm on NT based systems >> (since NT4 SP4), but the reason was a bit of "privacy paranoia", people >> didn't like to give away their MAC addresses through a GUID. >> >> Willy. >> >> > > Is the algorithm MS uses to create a GUID published somewhere? > > -Mark pseudorandom number generator inside CryptoAPI which in turn calls Win32's API CryptGenRandom().Note that COM uses the same Win32 API but now through CoCreateGuid(). I don't know the exact algorithm used by CryptGenRandom() and I don't think it's a trade secret so I would suggest you to ask MSFT for details by sending a mail to Brian LaMacchia b**@microsoft.com Willy. MAC addresses aren't used any more to generate GUID's.
Willy. Show quoteHide quote "Jonathan Allen" <x@x.x> wrote in message news:%23pL8IXsZFHA.2520@TK2MSFTNGP09.phx.gbl... > Probably not possible. Two computers would have to be built as exactly the > same time, have the same MAC address (normally impossible), and generate a > GUID at exactly the same time. (Actually, I vaguely remember that MS > doesn't use the MAC address anymore, but I may be mistaken.) > > -- > Jonathan Allen > > > "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message > news:OHlTnMsZFHA.2288@TK2MSFTNGP14.phx.gbl... >> Does anybody know the odds of generating a duplicate guid? >> >> -- >> Jay Douglas >> http://jaydouglas.com >> >> >> > > "Jay Douglas" <jayREMOVEIFNOTSPAM@squarei.com> wrote in message Better than the odds of an incrementing numeric counter generating a news:OHlTnMsZFHA.2288@TK2MSFTNGP14.phx.gbl... > Does anybody know the odds of generating a duplicate guid? > > -- > Jay Douglas > http://jaydouglas.com > > duplicate number. SP  |
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