1. A method for executing a safety-critical function of a computing unit in a cyber-physical system, the method comprising:receiving a request by a first computing unit in the cyber-physical system from a second computing unit, separate from the first computing unit, for an execution of the a safety-critical function at the first computing unit, the safety-critical function being a cryptographic operation;
acquiring at least one of an environment-specific measurement value and a user-specific measurement value by at least one sensor of the first computing unit, the environment-specific measurement value describing an environment of the first computing unit, the user-specific measurement value describing an interaction of a user with the first computing unit;
determining, by the first computing unit, whether the acquired at least one of the environment-specific measurement value and the user user-specific measurement value fulfills a specified criterion, wherein the specified criterion describe a specific manner in which the user interacts with the first computing unit;
in response to the determination that the values fulfills the specified criterion, executing, by the first computing unit, a physical unclonable function as the safety-critical function;
generating a cryptographic key by the physical unclonable function; and
encrypting communication between the first computing unit and second computing unit using the generated cryptographic key.