Labelling of secret information

1. A method of enabling selection of one or more pieces of secret information stored in a first entity without revealing the one or more pieces of secret information, the one or more pieces of secret information being one or more secret keys for use with a corresponding encryption or decryption function, the first entity also storing an identity of each of the one or more secret keys which are each indicative of an access permission to the first entity associated with each of the one or more pieces of secret information, the method comprising the steps of:

(a) a second entity selecting one or more pieces of secret information by requesting, from the first entity, one or more of the access permissions and the associated one or more of the key identities for the selected one or more of the pieces of secret information stored in the first entity together with said encryption or decryption function; and

(b) in response to the selection request, the first entity outputting the access permissions and key identities to the second entity for use with said encryption or decryption function stored in the second entity without outputting the one or more pieces of secret information.

2. A method according to claim 1 wherein each of the pieces of secret information has an associated index and the request in step (a) includes one or more of the indexes to identify those pieces of secret information for which the values are requested.

3. A method according to claim 1 wherein the request in step (a) is a request for the values all of the pieces of secret information and the response in step (b) orders the values such that the second entity can determine which values are associated with which piece of secret information, and can use the order to generate an index for the secret information.

4. A method according to claim 2 or claim 3 , further including the steps, in the first entity and following step (b), of:

(c) receiving a request from the second entity identifying a function and identifying the index of a piece of secret information to be used in performing the function; and

(d) performing the function using the identified piece of secret information.

5. A method according to claim 1 , further including the steps, in the first entity and following step (b), of:

(c) receiving a request from the second entity identifying a function and a piece of secret information to be used in performing the function; and

(d) performing the function using at least the identified piece of secret information, the identified piece of secret information being identified in the request of step (c) on the basis of at least one of the values output in step (b).

6. A method according to claim 1 , wherein the secret information is stored in one or more physical locations of the first entity, and wherein the values are not indicative of those physical locations.

7. A method according to claim 1 , wherein the first entity is implemented in a first integrated circuit and the second entity is implemented in a second integrated circuit.

8. A method according to claim 7 , wherein the first integrated circuit includes a memory for storing the pieces of secret information and the values.

9. A method according to claim 8 , including a plurality of the first integrated circuits, wherein the physical location of a piece of the secret information having particular attributes is mutually different for at least some of the first integrated circuits.

10. A method according to claim 1 , wherein the integrated circuit is programmed and configured to apply at least one of the encryption or decryption functions to data using the corresponding key as an operand.