Abstract: The invention enables a cryptographic device to be easily, securely and/or irreversibly customized to provide specified cryptographic functionality. For example, the invention can enable easy and secure modification (expansion, reduction or changing) of application code (which interacts with code stored on a cryptographic device) via the exposure of, for example, the mathematical primitive operations available on the cryptographic device. In particular, the invention can enable modification of available cryptographic operations at a relatively high level of programming abstraction, thus enabling such modification to be accomplished relatively easily. Further, the invention can enable the modification to be accomplished in a manner that does not necessitate or allow access by the application developer to other operations of the cryptographic device, thus providing security for the proprietary code and/or cryptographic keys of other persons or entities that may be present on the cryptographic device.

Abstract: A digitally controlled analog cancellation system containing an analog noise cancellation circuit with a residual microphone (39) with a digital virtual earth controller (40) for optimizing variable parameters employed in the analog cancellation circuit.