Balancing Privity and Enforceability of BPM-Based Smart Contracts on Blockchains

Abstract

Blockchains are a promising enabling technology for inter-organizational processes in untrusted environments and for the implementation of smart contracts in general. Smart contracts aim at three major objectives: observability, online enforceability and privity. Privity strives for limiting the sharing of information within a contract to those parties of a contract who have a contractual need to know. However, current BPM-based systems operating on blockchains do not address privity. The approaches deal with enforceability and privity as mutual exclusive properties. We show that the trade-offs between privity and enforceability can be considered in fine details and propose means to balance privity and enforceability in the design of smart contracts according to the application requirements. Besides this conceptual basis, we introduce patterns for encryption and key exchange allowing different levels of privity and for supporting proactive online enforceability in the presence of encrypted on-chain data.