The popularisation of blockchain-based applications made evident a critical challenge, namely the inherent isolation of these decentralised systems, akin to the disconnected and technologically diverse local area networks of the 1970s. This lack of interoperability limits the potential for widespread adoption and innovation in the blockchain space. While various initiatives aim to bridge this gap, many remain nascent. This paper addresses this issue by proposing a robust architecture and practical implementation to interconnect two Ethereum-based blockchains, enabling seamless smart contract interactions across these chains, and facilitating the exchange of complex information beyond mere token transfers. Our work explores the emerging landscape of Inter-Blockchain Communication (IBC) protocols, highlighting their current maturity and potential, and providing insights on how to overcome the technical hurdles associated with these protocols, particularly in the context of transmitting complex data and executing cross-chain function calls. Additionally, we tackle the challenges posed by linking private blockchains with public ones, ensuring secure and efficient data exchange. This paper aims to inspire blockchain researchers and practitioners, presenting a foundational framework for enhancing blockchain interoperability, including detailed, practical steps for its implementation. By laying the groundwork for more connected blockchain ecosystems, we intend to support the continued evolution and widespread adoption of blockchain technology.

The growing importance of traceability in supply chains necessitates robust, transparent, and efficient systems to ensure the integrity and authenticity of product journeys. This paper presents a comprehensive characterisation and data model for a generic traceability system, highlighting its implementation using smart contracts on Ethereum-compatible networks. The Ethereum Virtual Machine (EVM), with its pioneering role in smart contracts and extensive ecosystem, provides a robust environment for developing decentralised applications (dApps). We discuss the advantages of using blockchain technology to notarise traceability activities, ensuring immutability and transparency. Two main scenarios are explored: one where hash keys (cryptographic digests) are stored on-chain while detailed data remains off-chain, and another where all traceability data is fully stored on-chain. Each approach is evaluated for its impact on scalability, privacy, storage efficiency, and operational costs. The hash key method offers significant advantages in reducing blockchain storage costs, enhancing privacy, and maintaining data integrity, albeit with a dependency on reliable off-chain storage. Conversely, the full on-chain approach guarantees data immutability but at a higher cost and lower scalability. By combining these strategies, a balanced solution can be achieved, leveraging the strengths of both methods to provide a reliable, efficient, and secure traceability system. This paper aims to provide valuable insights for researchers and practitioners looking to implement or enhance traceability systems using blockchain technology, demonstrating how smart contracts can be effectively utilised to meet the demanding requirements of modern supply chains.