Lending Petri nets and contracts

Choreography-based approaches to service composition typically assume that, after a set of services has been found which correctly play the roles prescribed by the choreography, each service respects his role. Honest services are not protected against adversaries. We propose a model for contracts based on a extension of Petri nets, which allows services to protect themselves while still realizing the choreography. We relate this model with Propositional Contract Logic, by showing a translation of formulae into our Petri nets which preserves the logical notion of agreement, and allows for compositional verification

Renegotiation and recursion in Bitcoin contracts

BitML is a process calculus to express smart contracts that can be run on Bitcoin. One of its current limitations is that, once a contract has been stipulated, the participants cannot renegotiate its terms: this prevents expressing common financial contracts, where funds have to be added by participants at run-time. In this paper, we extend BitML with a new primitive for contract renegotiation. At the same time, the new primitive can be used to write recursive contracts, which was not possible in the original BitML. We show that, despite the increased expressiveness, it is still possible to execute BitML on standard Bitcoin, preserving the security guarantees of BitML.Comment: Full version of the paper presented at COORDINATION 202

Designing Secure Ethereum Smart Contracts: A Finite State Machine Based Approach

The adoption of blockchain-based distributed computation platforms is growing fast. Some of these platforms, such as Ethereum, provide support for implementing smart contracts, which are envisioned to have novel applications in a broad range of areas, including finance and Internet-of-Things. However, a significant number of smart contracts deployed in practice suffer from security vulnerabilities, which enable malicious users to steal assets from a contract or to cause damage. Vulnerabilities present a serious issue since contracts may handle financial assets of considerable value, and contract bugs are non-fixable by design. To help developers create more secure smart contracts, we introduce FSolidM, a framework rooted in rigorous semantics for designing con- tracts as Finite State Machines (FSM). We present a tool for creating FSM on an easy-to-use graphical interface and for automatically generating Ethereum contracts. Further, we introduce a set of design patterns, which we implement as plugins that developers can easily add to their contracts to enhance security and functionality

On Symbolic Verification of Bitcoin's script Language

Validation of Bitcoin transactions rely upon the successful execution of scripts written in a simple and effective, non-Turing-complete by design language, simply called SCRIPT. This makes the validation of closed scripts, i.e. those associated to actual transactions and bearing full information, straightforward. Here we address the problem of validating open scripts, i.e. we address the validation of redeeming scripts against the whole set of possible inputs, i.e. under which general conditions can Bitcoins be redeemed? Even if likely not one of the most complex languages and demanding verification problems, we advocate the merit of formal verification for the Bitcoin validation framework. We propose a symbolic verification theory for of open SCRIPT, a verifier tool-kit, and illustrate examples of use on Bitcoin transactions. Contributions include 1) a formalisation of (a fragment of) the language; 2) a novel symbolic approach to SCRIPT verification, suitable, e.g. for the verification of newly defined and non-standard payment schemas; and 3) building blocks for a larger verification theory for the developing area of Bitcoin smart contracts. The verification of smart contracts, i.e. agreements built as transaction-based protocols, is currently a difficult to formalise and computationally demanding problem

'Pencil Beamforming Increases Human Exposure to ElectroMagnetic Fields': True or False?

According to a very popular belief-very widespread among non-scientific communities-the exploitation of narrow beams, a.k.a. 'pencil beamforming', results in a prompt increase of exposure levels radiated by 5G Base Stations (BSs). To face such concern with a scientific approach, in this work we propose a novel localization-enhanced pencil beamforming technique, in which the traffic beams are tuned in accordance with the uncertainty localization levels of User Equipment (UE). Compared to currently deployed beamforming techniques, which generally employ beams of fixed width, we exploit the localization functionality made available by the 5G architecture to synthesize the direction and the width of each pencil beam towards each served UE. We then evaluate the effectiveness of pencil beamforming in terms of ElectroMagnetic Field (EMF) exposure and UE throughput levels over different realistic case-studies. Results, obtained from a publicly released open-source simulator, dispel the myth: the adoption of localization-enhanced pencil beamforming triggers a prompt reduction of exposure w.r.t. other alternative techniques, which include e.g., beams of fixed width and cellular coverage not exploiting beamforming. The EMF reduction is achieved not only for the UE that are served by the pencil beams, but also over the whole territory (including the locations in proximity to the 5G BS). In addition, large throughput levels-adequate for most of 5G services-can be guaranteed when each UE is individually served by one dedicated beam

Predicting global usages of resources endowed with local policies

The effective usages of computational resources are a primary concern of up-to-date distributed applications. In this paper, we present a methodology to reason about resource usages (acquisition, release, revision, ...), and therefore the proposed approach enables to predict bad usages of resources. Keeping in mind the interplay between local and global information occurring in the application-resource interactions, we model resources as entities with local policies and global properties governing the overall interactions. Formally, our model takes the shape of an extension of pi-calculus with primitives to manage resources. We develop a Control Flow Analysis computing a static approximation of process behaviour and therefore of the resource usages.Comment: In Proceedings FOCLASA 2011, arXiv:1107.584

Dapoxetine treatment in patients with lifelong premature ejaculation: the reasons of a Waterloo

Objective To assess both the acceptance and the discontinuation rates from dapoxetine, the first oral pharmacological agent indicated for the treatment of premature ejaculation (PE). Methods One hundred twenty consecutive potent patients (mean age 40.3 years; range 18-63 years) seeking medical treatment for lifelong PE were enrolled in a prospective phase II study. Moreover, they were assessed regarding detailed medical and sexual history, intravaginal ejaculatory latency time (IELT), International Index of Erectile Function (IIEF), and complete physical examination. The patients received a dapoxetine prescription (30 mg on demand) and unresponded cases received increased dose (60 mg after 3 months). The patients were evaluated at 1, 3, 6, and 12 months, and requested to complete a multiple-choice global assessment questionnaire regarding specific reasons for eventual therapy discontinuation. Results Twenty-four of the patients (20%) decided not to start dapoxetine. Fear of using a "drug" was the most frequently reported reason for treatment nonacceptance (50%) and the cost of treatment was the reason for 25% of the patients. Ninety-six patients (80%) started the therapy. Twenty-six percent dropped out after 1 month, 42.7% dropped out after 3 months, 18.7% dropped out at 6 months, 2% dropped out at 12 months, and 10.4% are continuing the therapy after 1 year. The main reasons were effect below expectations 24.4%, costs 22.1%, side effects 19.8%, loss of interest in sex 19.8%, and no efficacy 13.9%. Conclusion Twenty percent of lifelong PE patients seeking medical treatment for early ejaculation freely decided not to start treatment with dapoxetine, and roughly 90% of the patients who started therapy discontinued after 1 year. �� 2013 Elsevier Inc. All Rights Reserved

Regulating Data Exchange in Service Oriented Applications

We define a type system for COWS, a formalism for specifying and combining services, while modelling their dynamic behaviour. Our types permit to express policies constraining data exchanges in terms of sets of service partner names attachable to each single datum. Service programmers explicitly write only the annotations necessary to specify the wanted policies for communicable data, while a type inference system (statically) derives the minimal additional annotations that ensure consistency of services initial configuration. Then, the language dynamic semantics only performs very simple checks to authorize or block communication. We prove that the type system and the operational semantics are sound. As a consequence, we have the following data protection property: services always comply with the policies regulating the exchange of data among interacting services. We illustrate our approach through a simplified but realistic scenario for a service-based electronic marketplace

Human papillomavirus infection is not related with prostatitis-related symptoms: results from a casecontrol study.

PurposeTo investigate the relationship between human papillomavirus (HPV) infection and prostatitis-related symptoms.Materials and MethodsAll young heterosexual patients with prostatitis-related symptoms attending the same Center from January 2005 to December 2010 were eligible for this case-control study. Sexually active asymptomatic men were considered as the control group. All subjects underwent clinical examination, Meares-Stamey test and DNA-HPV test. Patients with prostatitis-related symptoms and asymptomatic men were compared in terms of HPV prevalence. Moreover, multivariable Cox proportional hazards regression analysis was performed to determine the association between HPV infection and prostatitis-related symptoms.ResultsOverall, 814 out of 2,938 patients (27.7%) and 292 out of 1,081 controls (27.0%) proved positive to HPV. The HPV genotype distribution was as follows: HR-HPV 478 (43.3%), PHR-HPV 77 (6.9%), LR-HPV 187 (16.9%) and PNG-HPV 364 (32.9%). The most common HPV genotypes were: 6, 11, 16, 26, 51, 53 and 81. No difference was found between the two groups in terms of HPV infection (OR 1.03; 95% CI 0.88-1.22; p = 0.66). We noted a statistically significant increase in HPV infection over the period 2005 to 2010 (p < 0.001) in both groups. Moreover, we found a statistically significant increase in HPV 16 frequency from 2005 to 2010 (p = 0.002).ConclusionsThis study highlights that prostatitis-like symptoms are unrelated to HPV infection. Secondary, we highlight the high prevalence of asymptomatic HPV infection among young heterosexual men

Human papillomavirus infection is not related with prostatitis-related symptoms: results from a casecontrol study.

This study highlights that prostatitis-like symptoms are unrelated to HPV infection. Secondary, we highlight the high prevalence of asymptomatic HPV infection among young heterosexual men