A security module for use with a terminal comprises a data interface adapted to be coupled to a terminal, for receiving at least part of an algorithm code or the complete algorithm code from the terminal, and a power interface for receiving supply power. A volatile memory coupled to the power interface in order to have power supplied thereto stores the part of the algorithm code or the complete algorithm code received via the data interface. A processor performs, the algorithm code in order to obtain an algorithm code result that can be delivered to the terminal. Due to storing at least part of an algorithm code in the volatile memory of the security module, the algorithm code of the security module is effectively protected against being detected by spying from a potential attacker.