855 research outputs found
The Transaction Graph for Modeling Blockchain Semantics
The advent of Bitcoin paved the way for a plethora of blockchain systems
supporting diverse applications beyond cryptocurrencies.
Although in-depth studies of the protocols, security, and privacy of
blockchains are available, there is no formal model of the transaction
semantics that a blockchain is supposed to guarantee.
In this work, we fill this gap, motivated by the observation that the
semantics of transactions in blockchain systems can be captured by a
directed acyclic graph. Such a transaction graph, or TDAG, generally
consists of the states and the transactions as transitions between the
states, together with conditions for the consistency and validity of
transactions. We instantiate the TDAG model for three prominent
blockchain systems: Bitcoin, Ethereum, and Hyperledger Fabric. We specify
the states and transactions as well as the validity conditions of the
TDAG for each one. This demonstrates the applicability of the model and
formalizes the transaction-level semantics that these systems aim for
SEMANTIC APPROACH TO SMART CONTRACT VERIFICATION
Vulnerabilities of smart contract are certainly one of the limiting factors for wider adoption of blockchain technology. Smart contracts written in Solidity language are considered due to common adoption of the Ethereum blockchain platform. Despite its popularity, the semantics of the language is not completely documented and relies on implicit mechanisms not publicly available and as such vulnerable to possible attacks. In addition, creating formal semantics for the higher-level language provides support to verification mechanisms. In this paper, a novel approach to smart contact verification is presented that uses ontologies in order to leverage semantic annotations of the smart contract source code combined with semantic representation of domain-specific aspects. The following aspects of smart contracts, apart from source code are taken into consideration for verification: business logic, domain knowledge, run-time state changes and expert knowledge about vulnerabilities. Main advantages of the proposed verification approach are platform independence and extendability
Inter-blockchain protocols with the Isabelle Infrastructure framework
The main incentives of blockchain technology are distribution and distributed change, consistency, and consensus. Beyond just being a distributed ledger for digital currency, smart contracts add transaction protocols to blockchains to execute terms of a contract in a blockchain network. Inter-blockchain (IBC) protocols define and control exchanges between different blockchains.
The Isabelle Infrastructure framework has been designed to serve security and privacy for IoT architectures by formal specification and stepwise attack analysis and refinement. A major case study of this framework is a distributed health care scenario for data consistency for GDPR compliance. This application led to the development of an abstract system specification of blockchains for IoT infrastructures.
In this paper, we first give a summary of the concept of IBC. We then introduce an instantiation of the Isabelle Infrastructure framework to model blockchains. Based on this we extend this model to instantiate different blockchains and formalize IBC protocols. We prove the concept by defining the generic property of global consistency and prove it in Isabelle
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