Abstract: This invention related to a method to validate a dynamic security code generated for a payment transaction, said method comprising the steps of: providing for a given payment transaction a dynamic security code associated to an identifier of said transaction; verifying using a verification memory if the provided dynamic security code has already been validated when associated to the same associated identifier; if not, verifying the validity of the provided dynamic security code; if the provided dynamic security code is valid, memorizing in the verification memory the provided dynamic security code, the associated identifier of the payment transaction.