US Patent 11593773 Payment transaction authentication system and method

This disclosure describes, in part, techniques for validating a money transfer request between a sender and a recipient via challenge questions. For instance, the method includes determining, by a payment service system, a level of risk associated with the money transfer request between the sender and the recipient; in response the level of risk being higher than a threshold, obtaining a query for the recipient, wherein the query is based at least on the current money transfer request or one or more past requests between the sender and recipient; receiving, from the recipient device, a response to the query; and validating the current payment transaction based on the response.