The github sourcecode is not open-source, but they've open-sourced a lot of other code in which they seem to be using Ruby's `SecureRandom::uuid()` function in

The github sourcecode is not open-source, but they've open-sourced a lot of other code in which they seem to be using Ruby's `SecureRandom::uuid()` function in the same kind of context for generating what they term 'opaque ids'.