require 'securerandom'
SecureRandom.uuid #=> "2d931510-d99f-494a-8c67-87feb05e1594"
SecureRandom.uuid #=> "bad85eb9-0713-4da7-8d36-07a8e4b00eab"
# UUID stands for Universally Unique IDentifier.
# It's a 128-bit value used for a unique identification in software
# development. UUID is the same as GUID (Microsoft) and is part of the
# Distributed Computing Environment (DCE), standardized by the Open
# Software Foundation (OSF). As mentioned, they are intended to have a
# high likelihood of uniqueness over space and time and are computationally
# difficult to guess. It's generation is based on the current timestamp and
# the unique property of the workstation that generated the UUID.

require 'securerandom'
SecureRandom.uuid # "2d931510-d99f-434a-8c87-87feb05e1594"
SecureRandom.uuid # "bad24eb6-0713-4da7-8d36-07a8e4b00eab"