The answer is: You should not need to know this. As stated in the accepted answer to a related question: A GUID doesn’t make guarantees about randomness, it makes guarantees around uniqueness. An even stronger statement on security and randomness is made in RFC4122, which speficies the UUID format: Do not assume that UUIDs are … Read more
Some good identifiers: MAC Address: It’s fairly easy to get at, and it’s usually unique. However, it can be spoofed/changed rather easily, so it depends on how unique it needs to be. CPU Serial Number: It’s not available on lots of older systems, but it’s there. Check out this MSDN page. It won’t change, but … Read more
SQLite itself does not support GUID as internal type. Except that, it does! (sort of). Remember, in SQLite any string can be used as type name, and that includes GUID or UUID (read more about SQLite datatypes). According to those rules, GUID type has affinity NONE, which is the same as for BLOB fields. With … Read more
just mask the 128bit int >>> import uuid >>> uuid.uuid4().int & (1<<64)-1 9518405196747027403L >>> uuid.uuid4().int & (1<<64)-1 12558137269921983654L These are more or less random, so you have a tiny chance of a collision Perhaps the first 64 bits of uuid1 is safer to use >>> uuid.uuid1().int>>64 9392468011745350111L >>> uuid.uuid1().int>>64 9407757923520418271L >>> uuid.uuid1().int>>64 9418928317413528031L These are … Read more
Here’s an excellent breakdown by Raymond Chen
If you read the Examples section from the GUID constructor, you’ll find your answer: Guid(1,2,3,new byte[]{0,1,2,3,4,5,6,7}) creates a Guid that corresponds to “00000001-0002-0003-0001-020304050607”. a is a 32-bit integer, b is a 16-bit integer, c is a 16-bit integer, and d is simply 8 bytes. Because a, b, and c are integer types rather than raw … Read more
You could just use the same Win32 API function that SQL Server uses: UuidCreateSequential and apply some bit-shifting to put the values into big-endian order. And since you want it in C#: private class NativeMethods { [DllImport(“rpcrt4.dll”, SetLastError=true)] public static extern int UuidCreateSequential(out Guid guid); } public static Guid NewSequentialID() { //Code is released into … Read more
You might want to check out this site: http://prettycode.org/2009/11/12/short-guid/ It looks very close to what you’re doing. public class ShortGuid { private readonly Guid guid; private readonly string value; /// <summary>Create a 22-character case-sensitive short GUID.</summary> public ShortGuid(Guid guid) { if (guid == null) { throw new ArgumentNullException(“guid”); } this.guid = guid; this.value = Convert.ToBase64String(guid.ToByteArray()) … Read more
The following Excel expression evaluates to a V4 GUID: =CONCATENATE(DEC2HEX(RANDBETWEEN(0,4294967295),8),”-“,DEC2HEX(RANDBETWEEN(0,65535),4),”-“,DEC2HEX(RANDBETWEEN(16384,20479),4),”-“,DEC2HEX(RANDBETWEEN(32768,49151),4),”-“,DEC2HEX(RANDBETWEEN(0,65535),4),DEC2HEX(RANDBETWEEN(0,4294967295),8)) -or (depending on locale setting/decimal and list separators)- =CONCATENATE(DEC2HEX(RANDBETWEEN(0;4294967295);8);”-“;DEC2HEX(RANDBETWEEN(0;65535);4);”-“;DEC2HEX(RANDBETWEEN(16384;20479);4);”-“;DEC2HEX(RANDBETWEEN(32768;49151);4);”-“;DEC2HEX(RANDBETWEEN(0;65535);4);DEC2HEX(RANDBETWEEN(0;4294967295);8)) Note that the first character of the third group is always 4 to signify a V4 (pseudo-random number generated) GUID/UUID per RFC 4122 section 4.4. Also note that the first character of the fourth group is … Read more
CREATE table test (testguid RAW(16) default SYS_GUID() ) This blog studied the relative performance.