CUB is a card block/unblock data requesting process between the issuer and the MULTOS KMA. When the issuer requests CUB data (card block and/or unblock), the MULTOS KMA replies with CUB response data, which includes the Card Block MAC and/or Card Unblock MAC. The card operator requires these MACs when he wishes to send Card Block command supported in MULTOS primitive. The blocked card will not respond to any application select command, until it is unblocked. Implementer MULTOS OS implementer, who develops the ROM mask for the MULTOS. KTU (Key Transformation Unit) A part of ALU, which contains decryption information when the ALU is encrypted. MAOSCO Limited A company owned by Mondex International Ltd. for the MULTOS license service and specification management.