Another commenter already posted but UUIDs (most platforms) and GUIDs (Microsoft platforms) are the best unique key and no need to hash them. Most larger web p

Another commenter already posted but UUIDs (most platforms) and GUIDs (Microsoft platforms) are the best unique key and no need to hash them. Most larger web products use them at least as a stamp or reference but many distributed systems (especially for sync) use them for simplicity but also globally uniqueness across many database domains. http://tools.ietf.org/html/rfc4122.html http://tools.ietf.org/html/rfc4122.html http://en.wikipedia.org/wiki/Universally_Unique_Identifier http://en.wikipedia.org/wiki/Universally_Unique_Identifier