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

A Semantic Framework for the Security Analysis of Ethereum smart contracts

Smart contracts are programs running on cryptocurrency (e.g., Ethereum) blockchains, whose popularity stem from the possibility to perform financial transactions, such as payments and auctions, in a distributed environment without need for any trusted third party. Given their financial nature, bugs or vulnerabilities in these programs may lead to catastrophic consequences, as witnessed by recent attacks. Unfortunately, programming smart contracts is a delicate task that requires strong expertise: Ethereum smart contracts are written in Solidity, a dedicated language resembling JavaScript, and shipped over the blockchain in the EVM bytecode format. In order to rigorously verify the security of smart contracts, it is of paramount importance to formalize their semantics as well as the security properties of interest, in particular at the level of the bytecode being executed. In this paper, we present the first complete small-step semantics of EVM bytecode, which we formalize in the F* proof assistant, obtaining executable code that we successfully validate against the official Ethereum test suite. Furthermore, we formally define for the first time a number of central security properties for smart contracts, such as call integrity, atomicity, and independence from miner controlled parameters. This formalization relies on a combination of hyper- and safety properties. Along this work, we identified various mistakes and imprecisions in existing semantics and verification tools for Ethereum smart contracts, thereby demonstrating once more the importance of rigorous semantic foundations for the design of security verification techniques.Comment: The EAPLS Best Paper Award at ETAP

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

Characterisation of expression patterns and functional role of Cactin in early zebrafish development

The immune system of teleost zebrafish (Danio rerio) shows high similarity to mammalian counterparts sharing many innate immune components including Toll-Like Receptors (TLRs), cytokines, chemokines and complement molecules. As in mammals, zebrafish also contains the transcription factor NF-jB that plays dualist roles in innate immunity and early development. Indeed NF-jB members are expressed in different temporal patterns during the early stages of zebrafish embryogenesis indicating that each molecule is involved in specific developmental events. In the present study we employ zebrafish as a model to characterise the expression pattern and role of a novel NF-jB regulator, termed Cactin, in early development. Cactin was first characterised in Drosophila as a new member of the Rel pathway that could affect the generation of dorsal–ventral polarity. To explore the potential developmental role of Cactin in zebrafish, we initially investigated its expression pattern and functional role during early embryonic developmental stages. We detect Cactin expression at all stages of early development and knockdown of Cactin by specific morpholino antisense oligonucleotides causes developmental abnormalities manifested by an overall dysmorphic cellular organisation. These results indicate that Cactin has been highly conserved during evolution and plays a key role in early embryonic development

Characterisation of expression patterns and functional role of Cactin in early zebrafish development

The immune system of teleost zebrafish (Danio rerio) shows high similarity to mammalian counterparts sharing many innate immune components including Toll-Like Receptors (TLRs), cytokines, chemokines and complement molecules. As in mammals, zebrafish also contains the transcription factor NF-jB that plays dualist roles in innate immunity and early development. Indeed NF-jB members are expressed in different temporal patterns during the early stages of zebrafish embryogenesis indicating that each molecule is involved in specific developmental events. In the present study we employ zebrafish as a model to characterise the expression pattern and role of a novel NF-jB regulator, termed Cactin, in early development. Cactin was first characterised in Drosophila as a new member of the Rel pathway that could affect the generation of dorsal–ventral polarity. To explore the potential developmental role of Cactin in zebrafish, we initially investigated its expression pattern and functional role during early embryonic developmental stages. We detect Cactin expression at all stages of early development and knockdown of Cactin by specific morpholino antisense oligonucleotides causes developmental abnormalities manifested by an overall dysmorphic cellular organisation. These results indicate that Cactin has been highly conserved during evolution and plays a key role in early embryonic development

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

An empirical analysis of smart contracts: platforms, applications, and design patterns

Smart contracts are computer programs that can be consistently executed by a network of mutually distrusting nodes, without the arbitration of a trusted authority. Because of their resilience to tampering, smart contracts are appealing in many scenarios, especially in those which require transfers of money to respect certain agreed rules (like in financial services and in games). Over the last few years many platforms for smart contracts have been proposed, and some of them have been actually implemented and used. We study how the notion of smart contract is interpreted in some of these platforms. Focussing on the two most widespread ones, Bitcoin and Ethereum, we quantify the usage of smart contracts in relation to their application domain. We also analyse the most common programming patterns in Ethereum, where the source code of smart contracts is available.Comment: WTSC 201

Mal Mediates TLR-Induced Activation of CREB and Expression of IL-10

TLRs initiate immune responses by direct detection of molecular motifs that distinguish invading microbes from host cells. Five intracellular adaptor proteins, each containing a Toll/IL-1R (TIR) domain, are used by TLRs and play key roles in dictating gene expression patterns that are tailored to the invader. Such gene expression is mediated by transcription factors, and although TIR adaptor-induced activation of NF-kB and the IFN regulatory factors have been intensively studied, there is a dearth of information on the role of TIR adaptors in regulating CREB. In this paper, we describe a role for the TIR adaptor Mal in enhancing activation of CREB. Mal-deficient murine bone marrow-derived macrophages show a loss in responsiveness to TLR2 and TLR4 ligands with respect to activation of CREB. Mal-deficient cells also fail to express the CREB-responsive genes IL-10 and cyclooxygenase 2 in response to Pam2Cys-Ser-(Lys)4 and LPS. We reveal that Mal-mediated activation of CREB is dependent on Pellino3 and TNFR-associated factor 6, because CREB activation is greatly diminished in Pellino3 knockdown cells and TNFRassociated factor 6-deficient cells. We also demonstrate the importance of p38 MAPK in this pathway with the p38 inhibitor SB203580 abolishing activation of CREB in murine macrophages. MAPK-activated protein kinase 2 (MK2), a substrate for p38 MAPK, is the likely downstream mediator of p38 MAPK in this pathway, because Mal is shown to activate MK2 and inhibition of MK2 decreases TLR4-induced activation of CREB. Overall, these studies demonstrate a new role for Mal as a key upstream regulator of CREB and as a contributor to the expression of both pro- and anti-inflammatory gen

Mal Mediates TLR-Induced Activation of CREB and Expression of IL-10

TLRs initiate immune responses by direct detection of molecular motifs that distinguish invading microbes from host cells. Five intracellular adaptor proteins, each containing a Toll/IL-1R (TIR) domain, are used by TLRs and play key roles in dictating gene expression patterns that are tailored to the invader. Such gene expression is mediated by transcription factors, and although TIR adaptor-induced activation of NF-kB and the IFN regulatory factors have been intensively studied, there is a dearth of information on the role of TIR adaptors in regulating CREB. In this paper, we describe a role for the TIR adaptor Mal in enhancing activation of CREB. Mal-deficient murine bone marrow-derived macrophages show a loss in responsiveness to TLR2 and TLR4 ligands with respect to activation of CREB. Mal-deficient cells also fail to express the CREB-responsive genes IL-10 and cyclooxygenase 2 in response to Pam2Cys-Ser-(Lys)4 and LPS. We reveal that Mal-mediated activation of CREB is dependent on Pellino3 and TNFR-associated factor 6, because CREB activation is greatly diminished in Pellino3 knockdown cells and TNFRassociated factor 6-deficient cells. We also demonstrate the importance of p38 MAPK in this pathway with the p38 inhibitor SB203580 abolishing activation of CREB in murine macrophages. MAPK-activated protein kinase 2 (MK2), a substrate for p38 MAPK, is the likely downstream mediator of p38 MAPK in this pathway, because Mal is shown to activate MK2 and inhibition of MK2 decreases TLR4-induced activation of CREB. Overall, these studies demonstrate a new role for Mal as a key upstream regulator of CREB and as a contributor to the expression of both pro- and anti-inflammatory gen

Determination of Pesticide Residues in IV Range Artichoke (Cynara cardunculus L.) and Its Industrial Wastes

Fourth-range products are those types of fresh fruit and vegetables that are ready for raw consumption or after cooking, and belong to organic or integrated cultivations. These products are subject to mild post-harvesting processing procedures (selection, sorting, husking, cutting, and washing), and are afterwards packaged in packets or closed food plates, with an average shelf life of 5–10 days. Artichokes are stripped of the leaves, stems and outer bracts, and the remaining heads are washed with acidifying solutions. The A LC-MS/MS analytical method was developed and validated following SANTE guidelines for the detection of 220 pesticides. This work evaluated the distribution of pesticide residues among the fraction of artichokes obtained during the industrial processing, and the residues of their wastes left on the field were also investigated. The results showed quantifiable residues of one herbicide (pendimethalin) and four fungicides (azoxystrobin, propyzamide, tebuconazole, and pyraclostrobin). Pendimethalin was found in all samples, with the higher values in leaves 0.046 ± 8.2 mg/kg and in field waste 0.30 ± 6.7 mg/kg. Azoxystrobin was the most concentrated in the outer bracts (0.18 ± 2.9 mg/kg). The outer bracts showed the highest number of residues. The industrial waste showed a significant decrease in the number of residues and their concentration