UUID.me Web Services and Universal Catalog A Universally Unique Identifier (UUID) is an identifier standard used in software construction, standardized by the Open Software Foundation (OSF) as part of the Distributed Computing Environment

A Universally Unique Identifier (UUID) is an identifier standard used in software construction, standardized by the Open Software Foundation (OSF) as part of the Distributed Computing Environment (DCE).

UUIDs are used extensively in the:

Technically a UUID is the same as a GUID however in these systems the UUID is used for entities and GUID for objects.

This site will be providing a web service for UUID catalog creation in conjunction with NAMSPACES.me

The intent of UUIDs is to enable distributed systems to uniquely identify information without significant central coordination. Thus, anyone can create a UUID and use it to identify something with reasonable confidence that the identifier will never be unintentionally used by anyone for anything else. Information labeled with UUIDs can therefore be later combined into a single database without needing to resolve name conflicts. The most widespread use of this standard is in Microsoft's Globally Unique Identifiers (GUIDs). Other significant users include Linux's ext2/ext3 filesystem, LUKS encrypted partitions, GNOME, KDE, and Mac OS X, all of which use implementations derived from the uuid library found in the e2fsprogs package.

UUIDs are documented as part of ISO/IEC 11578:1996 "Information technology -- Open Systems Interconnection -- Remote Procedure Call (RPC)" and more recently in ITU-T Rec. X.667 | ISO/IEC 9834-8:2005 (freely available). The IETF has published Proposed Standard RFC 4122 that is technically equivalent with ITU-T Rec. X.667 | ISO/IEC 9834-8.

Definition

A UUID is a 16-byte (128-bit) number. The number of theoretically possible UUIDs is therefore 2^16*8 = 2¹²⁸ = 256¹⁶ or about 3.4 × 10³⁸. This means that 1 trillion UUIDs would have to be created every nanosecond for 10 billion years to exhaust the number of UUIDs.

In its canonical form, a UUID consists of 32 hexadecimal digits, displayed in 5 groups separated by hyphens, in the form 8-4-4-4-12 for a total of 36 characters. For example:

550e8400-e29b-41d4-a716-446655440000

A UUID may also be used with a specific identifier intentionally used repeatedly to identify the same thing in different contexts. For example, in Microsoft's Component Object Model, every component must implement the IUnknown interface, which is done by creating a UUID representing IUnknown. In all cases wherever IUnknown is used, whether it is being used by a process trying to access the IUnknown interface in a component, or by a component implementing the IUnknown interface, it is always referenced by the same identifier: 00000000-0000-0000-C000-000000000046.

Version 1 (MAC address)

Conceptually, the original (version 1) generation scheme for UUIDs was to concatenate the UUID version with the MAC address of the computer that is generating the UUID, and with the number of 100-nanosecond intervals since the adoption of the Gregorian calendar. In practice, the actual algorithm is more complicated. This scheme has been criticized in that it is not sufficiently 'opaque'; it reveals both the identity of the computer that generated the UUID and the time at which it did so.

Version 2 (DCE Security)

Version 2 UUIDs are similar to Version 1 UUIDs, with the upper byte of the clock sequence replaced by the identifier for a "local domain" (typically either the "POSIX UID domain" or the "POSIX GID domain") and the first 4 bytes of the timestamp replaced by the user's POSIX UID or GID (with the "local domain" identifier indicating which it is).

Version 3 (MD5 hash)

Version 3 UUIDs use a scheme deriving a UUID via MD5 from a URL, a fully qualified domain name, an Object identifier, a distinguished name (DN as used in Lightweight Directory Access Protocol), or on names in unspecified namespaces. Version 3 UUIDs have the form


							xxxxxxxx-xxxx-3xxx-xxxx-xxxxxxxxxxxx

with hexadecimal digits x.

To determine the version 3 UUID of a given name the UUID of the namespace, e.g.


							6ba7b810-9dad-11d1-80b4-00c04fd430c8

for a domain, is transformed to a string of bytes corresponding to its hexadecimal digits, concatenated with the input name, hashed with MD5 yielding 128 bits. Six bits are replaced by fixed values, four of these bits indicate the version, 0011 for version 3. Finally the fixed hash is transformed back into the hexadecimal form with hyphens separating the parts relevant in other UUID versions.

Version 4 (random)

Version 4 UUIDs use a scheme relying only on random numbers. This algorithm sets the version number, as well as two reserved bits. All other bits are set using a random or pseudorandom data source.

Version 5 (SHA-1 hash)

Version 5 UUIDs use a scheme with SHA-1 hashing, otherwise it is the same idea as in version 3. RFC 4122 states that version 5 is preferred over version 3 name based UUIDs.

Source: Wiki