Efficient Conditional Proxy Re-encryption with Chosen-Ciphertext Security

Recently, a variant of proxy re-encryption, named conditional proxy re-encryption (C-PRE), has been introduced. Compared with traditional proxy re-encryption, C-PRE enables the delegator to implement fine-grained delegation of decryption rights, and thus is more useful in many applications. In this paper, based on a careful observation on the existing definitions and security notions for C-PRE, we reformalize more rigorous definition and security notions for C-PRE. We further propose a more efficient C-PRE scheme, and prove its chosenciphertext security under the decisional bilinear Diffie-Hellman (DBDH) assumption in the random oracle model. In addition, we point out that a recent C-PRE scheme fails to achieve the chosen-ciphertext security

Explaining the Frequency of Alcohol Consumption in a Conflict Zone: Jews and Palestinians in Israel

Experiencing stress and exposure to terrorism may have an adverse effect on health risk behaviors. Few studies have examined alcohol use among adults living in Israel under chronic, stressful terrorism-related conditions. In this study, we examined the relationships of demographics, past stressful events, and terrorism exposure to the frequency of alcohol use and the mediating roles of depressive and post-traumatic stress disorder (PTSD) symptoms. We used three waves of data from a 2007–2008 nationally representative sample of Jewish and Palestinian adults in Israel. We assessed past stressful events, in addition to direct and indirect exposures to terrorism. Results indicated that past stressful events and exposure to terrorism were not directly associated with alcohol use, but were indirectly associated and mediated by depressive and PTSD symptomology. Mental health symptoms were differentially associated with alcohol use. More frequent drinking was mediated by higher levels of depression, including for women and Palestinians; however, PTSD symptom severity was related to less frequent drinking. Mental health may play a prominent role in the frequency of alcohol use among adults exposed to terrorism in Israel. Alcohol use, as a coping mechanism, may differ by demographic characteristics (gender and ethnicity) and psychological symptomology for adults living in a conflict zone in Israel

Definition of experimental tests for a manned Mars excursion module. Volume 4 - Briefing brochure

Conceptual design and test program for manned Mars Excursion Module /MEM/ mission in 1980 perio

The impact of prior physical conditioning in initial recruit training success: A systematic review

Aim: To determine whether recruits who underwent a physical conditioning program prior to initial tactical training had increased rates of success.Design: Systematic ReviewMethod: A systematic search, following the PRISMA protocol and registered in the Open Science Framework, was conducted to identify relevant studies. Keywords, derived from three themes (physical conditioning, tactical, and recruits), were employed in the search of database CINAHL, ProQuest, PubMed, Scopus, SportDiscus, and Web of Science. Studies were screened against inclusion/exclusion criteria with data extracted and analyzed. The Joanna Briggs Institute critical appraisal tools were used to assess methodological quality of included studies by two authors independently with a Kappa analysis to determine inter-rater agreement.Results: Of 14,411 identified articles, 13 studies informed the review. The mean quality of studies was considered ‘good’ with a Kappa of 0.81 between raters. Seven studies identified that an increase in physical fitness, through use of preconditioning programs, resulted in lower rates of injury. Three studies attributed increased basic training pass rates to physical conditioning programs. However, three studies failed to find a change in attrition rates following the programs.Conclusion: The volume of evidence suggests that programs aimed at increasing muscular conditioning and aerobic endurance prior to tactical training would result in fewer injuries and increased pass rates although reductions in absolute attrition may not change.Key Practice Points:• Recruits are less likely to be injured if they are fitter and / or have completed additional training prior to completing training for a tactical occupation

Secure Two-Party Computation with Fairness -- A Necessary Design Principle

Protocols for secure two-party computation enable a pair of mutually distrustful parties to carry out a joint computation of their private inputs without revealing anything but the output. One important security property that has been considered is that of fairness which guarantees that if one party learns the output then so does the other. In the case of two-party computation, fairness is not always possible, and in particular two parties cannot fairly toss a coin (Cleve, 1986). Despite this, it is actually possible to securely compute many two-party functions with fairness (Gordon et al., 2008 and follow-up work). However, all two-party protocols known that achieve fairness have the unique property that the effective input of the corrupted party is determined at an arbitrary point in the protocol. This is in stark contrast to almost all other known protocols that have an explicit fixed round at which the inputs are committed. In this paper, we ask whether or not the property of not having an input committal round is inherent for achieving fairness for two parties. In order to do so, we revisit the definition of security of Micali and Rogaway (Technical report, 1992), that explicitly requires the existence of such a committal round. We adapt the definition of Canetti in the two-party setting to incorporate the spirit of a committal round, and show that under such a definition, it is impossible to achieve fairness for any non-constant two-party function. This result deepens our understanding as to the type of protocol construction that is needed for achieving fairness. In addition, our result discovers a fundamental difference between the definition of security of Micali and Rogaway and that of Canetti (Journal of Cryptology, 2000) which has become the standard today. Specifically, many functions can be securely computed with fairness under the definition of Canetti but no non-constant function can be securely computed with fairness under the definition of Micali and Rogaway

Ready student one: Simulation-based education, virtual reality, and the perception of stress

Aim: To investigate differences in the physiological perception of physiotherapy student stress undergoing two types of simulated environments.Design: Quasi-experimentalMethods: Students enrolled in a Doctor of Physiotherapy program were subjected to two stressors: a neurological patient simulation (SIM) and a free-roaming virtual reality (VR) immersive gaming scenario. Physiological parameters including respiratory rate, heart rate, skin temperature, salivary cortisol, and α- amylase were collected prior to, immediately post, and 15, 30, and 60 minutes after each scenario. NASA- task load index (TXL) assessed participants’ perceptions of stress prior to, and at the end of, each scenario. Repeated measures linear mixed model analysed the impact of sampling time, stressor, and their interaction on the physiological parameters and NASA-TXL.Results: The VR experience elicited a marked increase in cortisol concentration (1.7nmol/L SE 0.8, p=0.045) from baseline, but not α-amylase, levels immediately after the task. The SIM experience did not influence the concentration of salivary stress markers, although α-amylase concentrations were higher in samples obtained pre-SIM compared to pre-VR samples. NASA-TXL results indicated that students perceived themselves as performing worst and being more stressed, frustrated, and insecure prior to, and after, the SIM compared to the VR task.Conclusion: The SIM scenario had a greater anticipatory perceived stress while the VR immersive gaming experience highlighted greater post-event physiological response to stress

Intermolecular disulfide bond influences unphosphorylated STAT3 dimerization and function

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor activated by the phosphorylation of tyrosine 705 in response to many cytokines and growth factors. Recently, the roles for unphosphorylated STAT3 (U-STAT3) have been described in response to cytokine stimulation, in cancers, and in the maintenance of heterochromatin stability. It has been reported that U-STAT3 dimerizes, shuttles between the cytoplasm and nucleus, and binds to DNA, thereby driving genes transcription. Although many reports describe the active role of U-STAT3 in oncogenesis in addition to phosphorylated STAT3, the U-STAT3 functional pathway remains elusive.In this report, we describe the molecular mechanism of U-STAT3 dimerization, and we identify the presence of two intermolecular disulfide bridges between Cys367 and Cys542 and Cys418 and Cys426, respectively. Recently, we reported that the same cysteines contribute to the redox regulation of STAT3 signaling pathway both in vitro and in vivo The presence of these disulfides is here demonstrated to largely contribute to the structure and the stability of U-STAT3 dimer as the dimeric form rapidly dissociates upon reduction in the S-S bonds. In particular, the Cys367-Cys542 disulfide bridge is shown to be critical for U-STAT3 DNA-binding activity. Mutation of the two Cys residues completely abolishes the DNA-binding capability of U-STAT3. Spectroscopic investigations confirm that the noncovalent interactions are sufficient for proper folding and dimer formation, but that the interchain disulfide bonds are crucial to preserve the functional dimer. Finally, we propose a reaction scheme of U-STAT3 dimerization with a first common step followed by stabilization through the formation of interchain disulfide bond

Updatable Blockchains

Software updates for blockchain systems become a real challenge when they impact the underlying consensus mechanism. The activation of such changes might jeopardize the integrity of the blockchain by resulting in chain splits. Moreover, the software update process should be handed over to the community and this means that the blockchain should support updates without relying on a trusted party. In this paper, we introduce the notion of updatable blockchains and show how to construct blockchains that satisfy this definition. Informally, an updatable blockchain is a secure blockchain and in addition it allows to update its protocol preserving the history of the chain. In this work, we focus only on the processes that allow securely switching from one blockchain protocol to another assuming that the blockchain protocols are correct. That is, we do not aim at providing a mechanism that allows reaching consensus on what is the code of the new blockchain protocol. We just assume that such a mechanism exists (like the one proposed in NDSS 2019 by Zhang et. al), and show how to securely go from the old protocol to the new one. The contribution of this paper can be summarized as follows. We provide the first formal definition of updatable ledgers and propose the description of two compilers. These compilers take a blockchain and turn it into an updatable blockchain. The first compiler requires the structure of the current and the updated blockchain to be very similar (only the structure of the blocks can be different) but it allows for an update process more simple, efficient. The second compiler that we propose is very generic (i.e., makes few assumptions on the similarities between the structure of the current blockchain and the update blockchain). The drawback of this compiler is that it requires the new blockchain to be resilient against a specific adversarial behaviour and requires all the honest parties to be online during the update process. However, we show how to get rid of the latest requirement (the honest parties being online during the update) in the case of proof-of-work and proof-of-stake ledgers