libuuid

This is the universally unique ID library, part of util-linux-ng.

The libuuid library generates and parses 128-bit universally unique
id's (UUID's).  A UUID is an identifier that is unique across both
space and time, with respect to the space of all UUIDs.  A UUID can
be used for multiple purposes, from tagging objects with an extremely
short lifetime, to reliably identifying very persistent objects
across a network.

See also the "uuid" package, which is a separate implementation.