Abstract: A method is provided for loading a data stream for a software program from a program source onto a communication terminal, having the following steps: the data stream for the software program is split into a number of successive data blocks; a respective data block attribute is generated for at least two of the data blocks using a first mathematical one-way function; an overall attribute for the data stream is generated from the at least two data block attributes using a second mathematical one-way function; a digital signature is generated from the overall attribute using a secret key belonging to the program source; the signature and the at least two data block attributes are transmitted to the mobile communication terminal; the signature is verified by the mobile communication terminal using a public key which is stored in the communication terminal and is associated with the secret key belonging to the program source; and the software program is loaded onto the mobile communication terminal if the verific