Abstract: A method and device for authorizing execution of rented computer programs utilize a monostable element to determine usage time and a password to authorize use of the program for additional rental periods. The method and device involve a cartridge which is connected to the computer that executes the computer program. The cartridge is scanned in response to usage of the computer program (for example, the user typing on the computer keyboard). The scanning triggers a monostable element which remains in an active state for a predetermined amount of time, and time units are only counted while the monostable element is active. This permits a more accurate measurement of time during which the user is actually using the computer program. In order to authorize additional rental periods, a password scheme is utilized.

Abstract: Methods that enable the providing of authorization for the use of an instrument comprising a computer for a period limited by a date or limited to a number of hours. The method consists in mingling the data elements of the program memory to be protected according to a secret order. To use this memory, a transcoding device is then used. This transcoding device makes it possible to restore the right order of reading the instructions contained in the memory. This transcoding device is preferably in the form of a memory that contains several tables, only one of which gives the right transcoding data elements. The choice between these tables is made under control that make it possible to determine rights of access to the instrument. These are preferably assembled together in the form of a smart carrier that gets inserted between the normal carrier of the program memory and this program memory itself.