Tampering by office-based methadone maintenance patients with methadone take home privileges: a pilot study

Methadone Maintenance Treatment (MMT) is among the most widely studied treatments for opiate dependence with proven benefits for patients and society. When misused, however, methadone can also be lethal. The issue of methadone diversion is a major concern for all MMT programs. A potential source for such diversion is from those MMT patients who receive daily take home methadone doses. Using a reverse phase high performance liquid chromatography method, seven of the nine patients who were randomly selected to have all of their remaining methadone take home doses (within a 24 hour period) analyzed, returned lower than expected quantities of methadone. This finding suggests the possibility that such patients may have tampered with their daily take home doses. Larger prospective observational studies are clearly needed to test the supposition of this pilot study

Towards Non-Black-Box Separations of Public Key Encryption and One Way Function

Separating public key encryption from one way functions is one of the fundamental goals of complexity-based cryptography. Beginning with the seminal work of Impagliazzo and Rudich (STOC, 1989), a sequence of works have ruled out certain classes of reductions from public key encryption (PKE)---or even key agreement---to one way function. Unfortunately, known results---so called black-box separations---do not apply to settings where the construction and/or reduction are allowed to directly access the code, or circuit, of the one way function. In this work, we present a meaningful, non-black-box separation between public key encryption (PKE) and one way function. Specifically, we introduce the notion of $\textsf{BBN}^-$ reductions (similar to the $\textsf{BBN}\text{p}$ reductions of Baecher et al. (ASIACRYPT, 2013)), in which the construction $E$ accesses the underlying primitive in a black-box way, but wherein the universal reduction $R$ receives the efficient code/circuit of the underlying primitive as input and is allowed oracle access to the adversary $\textsf{Adv}$. We additionally require that the number of oracle queries made to $\textsf{Adv}$, and the success probability of $R$ are independent of the run-time/circuit size of the underlying primitive. We prove that there is no non-adaptive, $\textsf{BBN}^-$ reduction from PKE to one way function, under the assumption that certain types of strong one way functions exist. Specifically, we assume that there exists a regular one way function $f$ such that there is no Arthur-Merlin protocol proving that ``$z \not\in \textsf{Range}(f)$\u27\u27, where soundness holds with high probability over ``no instances,\u27\u27 $y \sim f(U_n)$, and Arthur may receive polynomial-sized, non-uniform advice. This assumption is related to the average-case analogue of the widely believed assumption $\textbf{coNP} \not\subseteq \textbf{NP}/\textbf{poly}$

Strong Parallel Repetition Theorem for Free Projection Games

The parallel repetition theorem states that for any two provers one round game with value at most 1 − ɛ (for ɛ < 1/2), the value of the game repeated n times in parallel is at most (1−ɛ 3) Ω(n / log s) where s is the size of the answers set [Raz98],[Hol07]. For Projection Games the bound on the value of the game repeated n times in parallel was improved to (1−ɛ2) Ω(n) [Rao08] and was shown to be tight [Raz08]. In this paper we show that if the questions are taken according to a product distribution then the value of the repeated game is at most (1 − ɛ2 Ω(n / log s) and if in addition the game is a Projection Game we obtain a strong parallel repetition theorem, i.e., a bound of (1 − ɛ) Ω(n).

Non-Malleable Coding Against Bit-wise and Split-State Tampering

Non-malleable coding, introduced by Dziembowski, Pietrzak and Wichs (ICS 2010), aims for protecting the integrity of information against tampering attacks in situations where error-detection is impossible. Intuitively, information encoded by a non-malleable code either decodes to the original message or, in presence of any tampering, to an unrelated message. Non-malleable coding is possible against any class of adversaries of bounded size. In particular, Dziembowski et al. show that such codes exist and may achieve positive rates for any class of tampering functions of size at most 22αn, for any constant α ∈ [0, 1). However, this result is existential and has thus attracted a great deal of subsequent research on explicit constructions of non-malleable codes against natural classes of adversaries. In this work, we consider constructions of coding schemes against two well-studied classes of tampering functions; namely, bit-wise tampering functions (where the adversary tampers each bit of the encoding independently) and the much more general class of split-state adversaries (where two independent adversaries arbitrarily tamper each half of the encoded sequence). We obtain the following results for these models. 1. For bit-tampering adversaries, we obtain explicit and efficiently encodable and decodable nonmalleabl

Effect of Micrometer-Scale Roughness of the Surface of Ti6Al4V Pedicle Screws in Vitro and in Vivo

Background: Titanium implants that have been grit-blasted and acid-etched to produce a rough microtopography support more bone integration than do smooth-surfaced implants. In vitro studies have suggested that this is due to a stimulatory effect on osteoblasts. It is not known if grit-blasted and acid-etched Ti6Al4V implants also stimulate osteoblasts and increase bone formation clinically. In this study, we examined the effects of micrometer-scale-structured Ti6Al4V surfaces on cell responses in vitro and on tissue responses in vivo