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On Parallel and Concurrent Security of HB and HB +. Jonathan Katz and Ji-Sun Shin University of Maryland. Motivation. Juels and Weis analyze and propose the HB and HB + protocols (tomorrow) Building on prior work of Hopper-Blum
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On Parallel and Concurrent Security of HB and HB+ Jonathan Katz and Ji-Sun Shin University of Maryland
Motivation • Juels and Weis analyze and propose the HB and HB+ protocols (tomorrow) • Building on prior work of Hopper-Blum • HB: secure against passive adversaryHB+: secure against active adversary • They are extremely efficient • Suitable for low-power devices
But… • Juels-Weis analyze “basic”, two-round protocols with soundness ½ • Then claim security under sequential repetition • Yields protocols with O(k) rounds! • Also, no security under concurrent executions…
Our Results • Using recent results of Regev (STOC ’05), we prove security of HB/HB+ under concurrent executions • HB/HB+ can be “collapsed” to only 2-3 rounds! • We believe our approach also greatly simplifies the proofs…