Device and method for securing software

A device includes a first memory unit adapted to store encrypted instructions, a processor adapted to execute decrypted instructions, a second memory unit accessible by the processor, and a decryption unit. The device includes a key database and a key selection circuit, wherein the key selection circuit is adapted to select a selected decryption key from the key database for decrypting encrypted instructions. The selection is responsive to a fixed selection information stored within the integrated circuit and to received key selection information. A method includes a stage of receiving encrypted instructions; and executing decrypted instructions by a processor. The method includes receiving key selection information, selecting a selected decryption key out of a key database in response to fixed selection information and to the received key selection information, and decrypting encrypted instructions using the selected decryption key.