The invention is directed to a data-processing system comprising a processor, a second encrypted cryptographic key stored in a first persistent memory, and a cryptographic co-processor that comprises a first register and a second register. The cryptographic co-processor serves for decrypting in a decryption step the second encrypted cryptographic key, thereby generating therefrom a second unencrypted cryptographic key that is usable by the processor for executing an operation. For the decryption step the first register is loadable with the second encrypted cryptographic key and the second register is loadable with a first cryptographic key. The resulting second unencrypted cryptographic key is maintainable in one of the registers for being used by the cryptographic co-processor for decrypting encrypted information or encrypting unencrypted information for the operation.