Personal GUIDs

I’ve always liked GUIDs, and I have always liked the idea of having “personal guids”. While everyone on the planet could be assigned a GUID, it would require some central authority to ensure each person only has one GUID rather than just generating a whole bunch. I like the idea that a GUID can be specifically for someone based on their details, not just freshly generated.

Type 5 GUIDs are perfect for this type of GUID use. A Type 5 GUID is based on a SHA1 hash of some arbitrary namespace ID, and then whatever values make sense for that namespace. So I shall create my own standard for assigning a GUID for everyone.

First I make an ID string that is flexible enough to include everyone, but unique for each person. Also it should be readily repeatable exactly the same way each time for the same person.

My ID format is simple: Its a UTF8 string in uppercase withe semi colons seperating the fields. There are 6 fields. The format is:


All values should be uppercase. DateOfBirth is of the format YYYYMMDD in 8 decimal digits. Gender is either ‘M’ or ‘F’. GivenNames may have multiple names, separated by a single space between names. There must be no padding within the fields.

An example ID string is:


Next I need an Namespace ID for this namespace I have created. A namespace ID is a GUID itself. I am assigning the GUID:  {5b390b3f-9a62-508a-b235-6e6e8d270720}. I could have generated any new GUID. However I decided to make a Type 5 GUID itself for the Namespace ID. The name GUID is the type 5 GUID of the URL of this article (

So the Type 5 GUID created from that Namespace ID and the ID string example above is {18448b15-02cc-58f2-857d-c7a2c07728d2}. This is a GUID that is specific to that ID and recreateable at anytime, as long as the name and birthdate and place doesn’t change!

I have modified the program I wrote to create the Type 5 GUIDs for URLs into creating personal GUIDs using this format. – C Source Code and Binaries for Windows, OSX, and Linux. This is free and unencumbered software released into the public domain.

Example usage:

>PersonalGuid.exe Doe John m Australia Sydney 19700101

So download and find your own personal GUID. Perhaps one day this will become the basis of an RFC defining this as a standard :-)


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