GUIDs (UUIDs) are not necessarily good for cryptography; some implementations or versions make it easy to predict subsequent values. Originally UUIDs were crea

GUIDs (UUIDs) are not necessarily good for cryptography; some implementations or versions make it easy to predict subsequent values. Originally UUIDs were created to provide uniqueness in cases when you didn't own the namespace: http://www.ietf.org/rfc/rfc4122.txt http://www.ietf.org/rfc/rfc4122.txt I'm trying to figure out a solution to a similar problem this week. I'm leaning towards an AES of an auto-increment ID + random salt and my coding partner wants to create a random MD5 hex digest and store it as a second key in the database. He's probably right but I'd like to avoid creating yet another index.