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Faraday-Shielded dc Stark-Shift-Free Optical Lattice Clock
Beloy, K.,Zhang, X.,McGrew, W. F.,Hinkley, N.,Yoon, T. H.,Nicolodi, D.,Fasano, R. J.,Schä,ffer, S. A.,Brown, R. C.,Ludlow, A. D. American Physical Society 2018 Physical Review Letters Vol.120 No.18
<P>We demonstrate the absence of a dc Stark shift in an ytterbium optical lattice clock. Stray electric fields are suppressed through the introduction of an in-vacuum Faraday shield. Still, the effectiveness of the shielding must be experimentally assessed. Such diagnostics are accomplished by applying high voltage to six electrodes, which are grounded in normal operation to form part of the Faraday shield. Our measurements place a constraint on the dc Stark shift at the 10(-20) level, in units of the clock frequency. Moreover, we discuss a potential source of error in strategies to precisely measure or cancel nonzero dc Stark shifts, attributed to field gradients coupled with the finite spatial extent of the lattice-trapped atoms. With this consideration, we find that Faraday shielding, complemented with experimental validation, provides both a practically appealing and effective solution to the problem of dc Stark shifts in optical lattice clocks.</P>
Differential Side Channel Analysis Attacks on FPGA Implementations of ARIA
ChangKyun Kim,Martin Schläffer,SangJae Moon 한국전자통신연구원 2008 ETRI Journal Vol.30 No.2
In this paper, we first investigate the side channel analysis attack resistance of various FPGA hardware implementations of the ARIA block cipher. The analysis is performed on an FPGA test board dedicated to side channel attacks. Our results show that an unprotected implementation of ARIA allows one to recover the secret key with a low number of power or electromagnetic measurements. We also present a masking countermeasure and analyze its second-order side channel resistance by using various suitable preprocessing functions. Our experimental results clearly confirm that second-order differential side channel analysis attacks also remain a practical threat for masked hardware implementations of ARIA.