Embedding data and information related to function with which data is associated into a payload

1. A method of generating and sending a message from a first entity to a second entity, the first entity being an authentication integrated circuit of a printer consumable and the second entity being an authentication integrated circuit of a printer, the method including the steps of:

determining the message including an action with respect to consumable state data stored by the first entity;

generating an authentication code on the basis of the action and a parameter by applying a one-way function to the action and parameter, the parameter being indicative of an attribute of the action; and

sending the message and authentication code from the first entity to the second entity.

2. A method of generating and sending a message from a first entity to a second entity, the first entity being an authentication integrated circuit of a printer consumable and including an identifier that distinguishes it from a plurality of other entities of other printer consumables, the second entity being an authentication integrated circuit of a printer, the method comprising the steps of:

determining the message including an action with respect to consumable state data stored by the first entity;

generating an authentication code on the basis of the action and a parameter by applying a one-way function to the action and parameter, the parameter being based on the identifier; and

sending the message and authentication code from the first entity to the second entity.

3. A method according to claim 1 or 2 , wherein the action is a function, and the parameter is indicative of the function.

4. A method according to claim 3 , wherein the entity is capable of generating messages for each of a plurality of types of function, and the parameter is indicative of the type of function comprised by the message that is sent.

5. A method according to claim 3 , wherein the message includes one or more operands of the function.

6. A method according to claim 5 , wherein the function is a read function and the one or more operands include an address to be read.

7. A method according to claim 5 , wherein the function is a write function and the one or more operands include data to be written.

8. A method according to claim 4 , wherein the types of function include at least a read and a write, wherein the authentication step produces a different authentication code depending upon whether the action is a read or a write.

9. A method according to claim 4 , wherein the authentication step produces includes authentication codes.