Key rotation on publish-subscribe system

The present disclosure relates to a method for a cryptographic key rotation in a publish-subscribe system providing a broker service for routing stored encrypted messages to one or more subscribers of the topic to which the routed messages are assigned. The routing comprises decrypting the stored encrypted messages. The cryptographic key rotation comprises a re-encryption of the stored messages using a cryptographic replacement key. The re-encryption is executed by an encryption module of the publish-subscribe system as a background process, while the broker service is continued.