Patent ID: 11870887
Assignee: ASSA ABLOY AB
Field: Digital communication (Electrical engineering)
Classification: CPC H | IPC H

Claim 0:
1. A method for managing central secret keys of a plurality of user devices associated with a single public key, the method being performed in a key manager and comprising:
receiving, from a first user device, transformation data and an identifier of a second user device;
obtaining, from a data memory, a first central secret key associated with the first user device associated with the single public key;
generating a second central secret key by applying the transformation data to the first central secret key, wherein the transformation data is applied in reverse to how the transformation data is applied by the first user device to a first device secret key of the first user device to generate a second device secret key, for transfer to the second user device, to ensure the second central secret key and the second device secret key are also associated with the single public key;
storing the second central secret key in association with the second user device; and
generating an evolved second central secret key by applying a computation to the second central secret key, wherein the computation is applied in reverse to how the computation is applied by the second user device to the second device secret key transferred to the second user device from the first user device, based on secure communication between the key manager and the second user device, resulting in an evolved second device secret key and the evolved second central secret key,
wherein the first user device is unable to generate the evolved second device secret key without transformation data used in the computation, and wherein both the evolved second device secret key and the evolved second central secret key are also associated with the single public key.