PC Toledo

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In the OSF-specified algorithm for generating new (V1) GUIDs, the user's network card MAC address is used as a base for the last group of GUID digits, which means, for example, that a document can be tracked back to the computer that created it. This privacy hole was used when locating the creator of the Melissa virus.[6] Most of the other digits are based on the time while generating the GUID.

The other parts of a V1 GUID make use of the time since the implementation of the Gregorian calendar in 1582. V1 GUIDs, containing a MAC address and time, can be identified by the digit "1" in the first position of the third group of digits, for example {2F1E4FC0-81FD-11DA-9156-00036A0F876A}. Version 1 GUIDs generated between about 1995 and 2010 have Data3 starting with 11D, while more recent ones have 11E.

Version 4 GUIDs simply use a pseudo-random number for filling in all but six of the bits. They have a "4" in the 4-bit version position, and the first two bits of 'data4' are 1 and 0 (so the first hex digit of 'data4' is 8, 9, A, or B), for example {38A52BE4-9352-453E-AF97-5C3B448652F0}. More specifically, the 'data3' bit pattern would be 0001xxxxxxxxxxxx in V1, and 0100xxxxxxxxxxxx in V4. Cryptanalysis of the WinAPI GUID generator shows that, since the sequence of V4 GUIDs is pseudo-random, given full knowledge of the internal state, it is possible to predict previous and subsequent values.[7]

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   srand (clock());
    unsigned char GUID[40] = {0};
    int t = 0;
    char *szTemp = "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx";
    char *szHex = "0123456789ABCDEF-";
    int nLen = strlen (szTemp);

    for (t=0; t<nLen+1; t++)
    {
   int r = rand () % 16;
    char c = ' ';

    switch (szTemp[t])
   {
   case 'x' : { c = szHex [r]; } break;
    case 'y' : { c = szHex [r & 0x03 | 0x08]; } break;
    case '-' : { c = '-'; } break;
    case '4' : { c = '4'; } break;
    }

   GUID[t] = ( t < nLen ) ? c : 0x00;
    }

   printf ("%s\r\n", GUID);
   }

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PROCEDURE Main

   LOCAL cTemp := "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx"
   LOCAL cHex  := "0123456789ABCDEF-"
   LOCAL oElement, r

   FOR EACH oElement IN cTemp
      // r = rand () % 16

      DO CASE
      CASE oElement == "-"
      CASE oElement == "4"
      CASE oElement == "x" ; oElement := oElement // int r = rand () % 16; { c = szHex [r]; } // Hex( r )
      CASE oElement == "y" ; oElement := oElement // { c = szHex [r & 0x03 | 0x08]; } // Substr( szHex, r ? 0x03 ? 0x08, 1 )
      ENDCASE
   NEXT

   ? cTemp

   RETURN

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   #pragma BEGINDUMP

   #pragma comment( lib, "shell32.lib" )
   #include "hbapi.h"
   #include <windows.h>

   //------------------------------------------------------------------
   // standard 32 byte's M$ guid
   // Link: http://forums.fivetechsupport.com/viewtopic.php?f=3&t=28026&p=156570&hilit=guid#p156570
   // Link: http://forums.fivetechsupport.com/viewtopic.php?f=3&t=21719&start=30
   //------------------------------------------------------------------
   HB_FUNC( NEWGUID32 )
   {
   GUID guid;
    char obuff[38];
    memset( obuff, 0x0, 38 );
    if ( CoCreateGuid(&guid) == NULL )
   {
   OLECHAR tmpbuff[76];
    StringFromGUID2(&guid,tmpbuff,76);
    WideCharToMultiByte(CP_OEMCP,0,tmpbuff,-1,obuff,38,NULL,NULL);
    }
   hb_retclen(obuff,38);
    }
    
   #pragma ENDDUMP

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static function random_uuid()

return hb_strformat( "%04x%04x-%04x-%04x-%04x-%04x%04x%04x",;
                     hb_Random( 0, 0xffff ), hb_Random( 0, 0xffff ),;
                     hb_Random( 0, 0xffff ),;
                     hb_BitOr( Int( hb_Random( 0, 0x0fff ) ), 0x4000 ),;
                     hb_BitOr( Int( hb_Random( 0, 0x3fff ) ), 0x8000 ),;
                     hb_Random( 0, 0xffff ), hb_Random( 0, 0xffff ), hb_Random( 0, 0xffff ) )