Blockchain beyond immutability: Application firewalls on ethereum-based platforms

Blockchain is a technology that gained relevance in various fields due to its transparency and security in recording information in a reliable and immutable manner. In particular, the adoption of private blockchain platforms based on the Ethereum technology grew significantly in enterprise environments. However, there are certain issues concerning privacy and access control that may pose significant challenges in scenarios where private transactions occur between user agents instead of nodes, that is, between blockchain accounts that are not necessarily attached to specific nodes. The Blockchain Application Firewall (BAF) is introduced as a conceptual framework that can be applied in cases where control over data access is needed, including private transactions between accounts. More specifically, the BAF is intended to complement a blockchain endpoint acting as an intermediary between users and blockchain services and data, monitoring and controlling incoming and outgoing traffic, according to an applied access policy. This work investigates BAF’s feasibility and effectiveness in enhancing the capabilities of Ethereum-based blockchains in the described scenarios. A proof-of-concept was implemented with Besu to assess its feasibility, providing evidence that BAF can act as an additional layer of control over data stored, helping to solve key limitations in practical implementations and allowing exploration of new use cases that could not be addressed so far.