A method and apparatus for the digital signing of a message to be signed,
the message to be signed is transmitted via a communication network to a
mobile radio telephone to be used as a signing unit. A message to be
signed is transmitted from a transmitter to a receiver and then from the
receiver to the mobile radio telephone via a telephone network. The
mobile radio telephone user indicates that the message to be signed
should be signed, and the mobile radio telephone generates a signed
message. The signed message is then transmitted from the mobile radio
telephone to the receiver and from the receiver to an addressee.