An encrypting keypad module (30) comprising a keypad (40) and an encryption unit (42) is described. The encryption unit (42) includes an interpreter (56) for receiving a file (150) containing data and instructions for processing the data. The encryption unit (42) is operable to process the data in the file (150) by interpreting the instructions in the file (150). This enables a file (150) to be used to instruct the encryption unit (42) about the data that is to be operated on and the type of operations to be performed on the data.