Method for transmitting information between a computerized control center and a plurality of electronic franking machines

A method for transmitting information between a computerized control center and a plurality of electronic franking machines, at least in order that the center may transmit a counter reload instruction to each of the said machines the method comprising the steps of:

• keeping, for each machine of said plurality of machines, both in a secure memory in said center and in a secure memory in said each machine, a plurality of units of secret information each available for any future transmission of information from said center to said each machine, and
• transmitting information to be protected from fraud, such as said reload instruction, from said center to a determined machine of said plurality of machines, said step of transmitting including the substeps of,
• providing for a portable object having a memory in which writing and reading of data are free,
• selecting at said center a determined unit of information amongst said plurality of units kept for said determined machine,
• writing to said memory of said portable object with a writing means controlled by said center, data including an authentication means adapted to be prepared and verified only if said determined unit of information is known,
• transporting said portable object to said determined machine,
• reading said data from said memory of said portable object, with a reading means provided in said determined machine and
• taking into account said data in said determined machine only after verification of said authentication means.