PCA issues. It is in fact an embodiment of the role of an identity provider in a ticket-based identity management (IDM) system. That TC can be used to model IDM was outlined in [@KuntzeSchmidt2006A; @KuntzeSchmidt2006C], and is presented here for the first time in detail.

Though the separation of duties between PCA and CP allows in principle even for anonymity of the person using a TA, since only upon charging this person must be identified by credit card account or other means, this may not be the best option. In fact this would loose some accountability of the TA users. While RS may be able to obtain personal identities from PCA if pertinent contractual relationships are in place[, [e.g.]{},]{}if fraud by a TA user is suspected, data protection regulations may prevent a CP from unveiling personal identities. A second role played by the PCA is the initiation of charging. With respect to the revenues from ticket sales, a natural approach is a sharing between RS and PCA (and CP for its service). RS and PCA negotiate and implement policies for authorisation within the ticket acquisition and redemption processes[, [e.g.]{},]{}to prevent double spending or to blacklist misbehaving users. In collaboration between 