Method for securely storing variable data

Procedure for tuning the inventory data in a device data processing (22) of an electronic franking machine (12) comprising a memory of active balance (26) for a balance of postage and clearance mechanism (42) a data center (18) comprising a memory liquidation (46) for franking machine, carrying out the tuning of inventory data into two autonomous transactions for fixed storage of a default valid or recharge with valid default value stored where in a first transaction set to the franking machine (12) a way to change the value at which the stored default value can be confirmed, optionally without modification closing the transaction without a value change occurs or to modify a predetermined value stored and displayed on the franking machine, it is transmitted to the data center (18) a new default value inserted into the franking machine by exchanging coded messages or criptomensajes between the franking machine (12) and the data center (18), storing it in a respective memory default values ​​(28, 45) of the franking machine (12) and data center (18) and that after completing the first transaction is optionally adjusted mode postage or recharge mode, adding in a second transaction, which includes the exchange of criptomensajes between the franking machine (12) and the data center, the predetermined value stored in the respective memory defaults (28), the value stored in the memory of active balance (26) of the franking machine (12) and memory clearance (46) in the data center.