Economics

Intrinsic noise sources and their correlation in gallium-nitride high electron-mobility transistors are extracted and studied. Microwave noise measurements have been performed over the frequency range of 0.8-5.8 GHz. Using measured noise and scattering parameter data, the gate and drain noise sources and their correlation are determined using an equivalent-circuit representation. This model correctly predicts the frequency-dependent noise for two devices having different gate length. Three noise mechanisms are identified in these devices, namely, those due to velocity fluctuation, gate leakage, and traps.

A nonlinear field-effect transistor equivalent-circuit model is examined to identify the fundamental mechanisms that up-convert baseband 1 noise to near-carrier sideband noise when the device is operated in the large-signal regime. This model captures all physical noise sources and nonlinearities in the transistor, and thereby allows a general cause-and-effect treatment. The noise sources in the equivalent-circuit model are determined using low-frequency spectrum analyzer and microwave noise-figure meter data. Using the example of an AlGaN/GaN high electron-mobility transistor, the developed model correctly describes both the measured near-carrier sideband amplitude and phase noise simultaneously.

A numerical approach to simulate the intrinsic noise sources within transistors is described, and the impact of spatial correlation between local fluctuations is investigated. Using a 2-D numerical device solver, spectral densities for the gate and drain noise current sources and their correlation are evaluated using a Green's function approach, which is an equivalent of Shockley's impedance field method. Case studies with an AlGaN/GaN high electron mobility transistor are supported by measurement data. Using a spatial noise source correlation model, similar terminal noise is found to the case of an uncorrelated diffusion noise source. Therefore, using uncorrelated local noise sources to calculate the intrinsic terminal noise is found to be valid even for the submicrometer gate length field-effect transistor studied.

This paper describes saturation attacks on reduced-round versions of Skipjack. To begin with, we will show how to construct a 16-round distinguisher which distinguishes 16 rounds of Skipjack from a random permutation. The distinguisher is used to attack on 18(5∼22) and 23(5∼27) rounds of Skipjack. We can also construct a 20-round distinguisher based on the 16-round distinguisher. This distinguisher is used to attack on 22(1∼22) and 27(1∼27) rounds of Skipjack. The 80bit user key of 27 rounds of Skipjack can be recovered with 2 50 chosen plaintexts and 3 · 2 75 encryption times.

This paper describes saturation attacks on reduced-round versions of Skipjack. To begin with, we will show how to construct a 16-round distinguisher which distinguishes 16 rounds of Skipjack from a random permutation. The distinguisher is used to attack on 18(5∼22) and 23(5∼27) rounds of Skipjack. We can also construct a 20-round distinguisher based on the 16-round distinguisher. This distinguisher is used to attack on 22(1∼22) and 27(1∼27) rounds of Skipjack. The 80bit user key of 27 rounds of Skipjack can be recovered with 2 50 chosen plaintexts and 3 · 2 75 encryption times.