A data processing method accepts a removable storage media, which becomes electrically engaged with a system unit within the data processing system, after which the removable storage media and the hardware security unit mutually authenticate themselves. The removable storage media stores a private key of a first asymmetric cryptographic key pair and a public key of a second asymmetric cryptographic key pair that is associated with the hardware security unit, and the hardware security unit stores a private key of the second asymmetric cryptographic key pair and a public key of the first asymmetric cryptographic key pair that is associated with the removable storage media. In response to successfully performing the mutual authentication operation between the removable storage media and the hardware security unit, the system unit is enabled to invoke cryptographic functions on the hardware security unit while the removable storage media remains engaged with the system unit.