UUID v4 Generator

A universally unique identifier (UUID) is a 128-bit identifier that is generated using a cryptographically secure random number generator. As in other UUIDs, 4 bits are used to indicate version 4, and 2 bits are used to indicate the variant. Thus, 6 bits are constant, leaving 122 bits for the randomly generated part, for a total of 2122 (5.3×1036, 5.3 undecillion) possible values.