A data structure is provided for use as a positive list in a device, including an entry for each permitted communication partner of the device having a first identifier that explicitly identifies the communication partner, a value of a predetermined certificate field that identifies a certificate as explicitly associated with the communication partner, and a respective check value from at least one certificate of a communication partner that explicitly identifies the certificate. A method for updating the positive list for certificates from permitted communication partners of a device comprises the method steps of receiving a new certificate from a communication partner in the device, checking whether the positive list has an entry having an identifier of the communication partner and a value of a predetermined certificate field from the new certificate.