A method including obtaining a unique identifier for a user. The method also can include causing an authentication code to be sent to a device of the user. The method additionally can include receiving, through a first user interface displayed to the user, the authentication code. The method further can include displaying, to the user through the first user interface, a list of cards in a shared wallet for the user. The cards can be issued from multiple different issuers. The shared wallet can be accessible to multiple different merchants. The method additionally can include receiving, through the first user interface displayed to the user, a selection from the user of a selected card from the list of the cards for processing a transaction. The method further can include providing card information for the selected card to a merchant for processing the transaction. Other embodiments of related systems and methods are described.