I'm curious as to the OP's source as well. I found a recent investigatory paper at https://github.com/AdamISZ/ConfidentialTransactionsDoc/blob/... but nothing official.

Note that Confidential Transactions (CT) are a different technology. While ring signatures hides sender/receiver identity, CT hides transaction amounts.

Confusingly, plain CT actually uses ring sigs as part of the crypto, but not the kind that hides sender / receiver, rather as part of the commitment scheme.