Rerandomization is a strategy for improving balance on observed covariates in randomized controlled trials. It has been both advocated and advised against by renowned scholars of experimental design. However, the relationship and differences between stratification, rerandomization, and the combination of the two have not been previously investigated. In this paper, we show that stratified designs can be recreated by rerandomization and explain why, in most cases, stratification on binary covariates followed by rerandomization on continuous covariates is more efficient than rerandomization on all covariates at the same time.

Oblivious transfer is one of the main pillars of modern cryptography and plays a major role as a building block for other more complex cryptographic primitives. In this work, we present an efficient and versatile framework for oblivious transfer (OT) using one-round key-exchange (ORKE), a special class of key exchange (KE) where only one message is sent from each party to the other. Our contributions can be summarized as follows: - We analyze carefully ORKE schemes and introduce new security definitions. Namely, we introduce a new class of ORKE schemes, called Alice-Bob one-round key-exchange (A-B ORKE), and the definitions of message and key indistinguishability. - We show that OT can be obtained from A-B ORKE schemes fulfilling message and key indistinguishability. We accomplish this by designing a new efficient, versatile and universally composable framework for OT in the Random Oracle Model (ROM). The efficiency of the framework presented depends almost exclusively on the efficiency of the A-B ORKE scheme used since all other operations are linear in the security parameter. Universally composable OT schemes in the ROM based on new hardness assumptions can be obtained from instantiating our framework. Examples are presented using the classical Diffie-Hellman KE, RLWE-based KE and Supersingular Isogeny Diffie-Hellman KE.

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Let$G$denote a totally disconnected locally compact metric abelian group with translation invariant metric$d$and character group$Γ$_{$G$}. The Lipschitz spaces are defined by $$Lip\left( {\alpha ;p} \right) = \left\{ {f \in L^p \left( G \right):\left\| {\tau _a f - f} \right\|_p = O\left( {d\left( {a,0} \right)^\alpha } \right),a \to 0} \right\},$$ where$τ$_{$a$}$f$:$x$→$f$($x-a$) and α∈(0,1). For a suitable choice of metric it is shown that Lip (α;$p$)⊂$L$^{$r$}($Γ$_{$G$}), where α>1/$p$+1/$r$−1≧0 and 1≦$p$≦2. In the case$G$is compact the corresponding result holds for α>1/$r$−1/2 and$p$>2. In addition for$G$non-discrete the above result is shown to be sharp, in the sense that the range of values of α cannot be extended. The results include classical theorems of S. N. Bernstein, O. Szász and E. C. Titchmarsh.

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