Biblio

The concept of usage control goes beyond traditional access control by regulating not only the retrieval but also the processing of data. To be able to remotely enforce usage control policy the processing party requires a trusted execution environ-ment such as Intel SGX which creates so-called enclaves. In this paper we introduce Multi Enclave based Code from Template (MECT), an SGX-based architecture for trusted remote policy enforcement. MECT uses a multi-enclave approach in which an enclave generation service dynamically generates enclaves from pre-defined code and dynamic policy parameters. This approach leads to a small trusted computing base and highly simplified attestation while preserving functionality benefits. Our proof of concept implementation consumes customisable code from templates. We compare the implementation with other architectures regarding the trusted computing base, flexibility, performance, and modularity. This comparison highlights the security benefits for remote attestation of MECT.

The capability of executing so-called smart contracts in a decentralised manner is one of the compelling features of modern blockchains. Smart contracts are fully fledged programs which cannot be changed once deployed to the blockchain. They typically implement the business logic of distributed apps and carry billions of dollars worth of coins. In that respect, it is imperative that smart contracts are correct and have no vulnerabilities or bugs. However, research has identified different classes of vulnerabilities in smart contracts, some of which led to prominent multi-million dollar fraud cases. In this paper we focus on vulnerabilities related to integer bugs, a class of bugs that is particularly difficult to avoid due to some characteristics of the Ethereum Virtual Machine and the Solidity programming language. In this paper we introduce Osiris – a framework that combines symbolic execution and taint analysis, in order to accurately find integer bugs in Ethereum smart contracts. Osiris detects a greater range of bugs than existing tools, while providing a better specificity of its detection. We have evaluated its performance on a large experimental dataset containing more than 1.2 million smart contracts. We found that 42,108 contracts contain integer bugs. Besides being able to identify several vulnerabilities that have been reported in the past few months, we were also able to identify a yet unknown critical vulnerability in a couple of smart contracts that are currently deployed on the Ethereum blockchain.