Cold Resistors: Theory, Design and a Related Security Application

Abstract

A cold resistor is a device/circuitry/system emulating an active resistor which has lower effective noise temperature than the temperature of its environment. This dissertation contains three main studies of the cold resistor: theory, design and a related security application.

In the first study, a linear system that can imitate a “low-temperature” linear resistor while the circuitry is at room temperature without the usage of phase transition, valves, switches, non-linearity or measurements/control is introduced. It is demonstrated with both the theory analysis and the circuit simulation. It can be used as a plugin resistor at noise-sensitive places. The lowest effective noise temperature of the “cold” resistor is about 3 K, which is liquid Helium temperature.

In the second study, the correct and complete circuit theoretical model of cold resistors is conceived and developed. A practical “design tool” that shows the relationship of the lowest effective temperature versus the effective resistance of the cold resistor system is deduced. The theory and the design tool are confirmed by simulation results of the circuits.

In the third study, an expanded cold resistor scheme is introduced and explored to become a secure key exchanger. A circuit model of the system is conceived and simulated. This system is proved to be secure in the steady-state. The security vulnerability of the system which is due to the transients between different exchanged bits is found and discussed.