The coded, respectively uncoded 8-byte key, used to trigger certain card functions like “opening” the card.

The Masterkey can be calculated from the sum of the hexserial and the provider group.

So the mathematical formula is simply: hexserial + provider group = master key.

The Masterkey is also sometimes referred to as Key00. Whenever the Masterkey is written to the card, that is done uncoded (the plainmasterkey). The plainmasterkey is necessary for further processing of the key- and channel information.