Reliable Communication in Hybrid Authentication and Trust Models

TL;DR

This work addresses reliable communication (RC) in distributed networks under a hybrid authentication model that combines authenticated links, authenticated processes, and potential trusted components. It extends classical RC protocols (DolevU and SigFlood) to exploit trusted nodes and components, and introduces DualRC, which fuses path-based and signature-based dissemination to maximize RC coverage. The paper presents two correctness verification approaches—max-flow on a transformed graph and topology-driven graph simplification—to decide RC-Validity on a given network, along with complexity analyses. Together, these contributions broaden the set of network topologies where RC can be guaranteed and provide practical tools for verifying RC under realistic hybrid fault models.

Abstract

Reliable communication is a fundamental distributed communication abstraction that allows any two nodes of a network to communicate with each other. It is necessary for more powerful communication primitives, such as broadcast and consensus. Using different authentication models, two classical protocols implement reliable communication in unknown and sufficiently connected networks. In the first one, network links are authenticated, and processes rely on dissemination paths to authenticate messages. In the second one, processes generate digital signatures that are flooded in the network. This work considers the hybrid system model that combines authenticated links and authenticated processes. We additionally aim to leverage the possible presence of trusted nodes and trusted components in networks, which have been assumed in the scientific literature and in practice. We first extend the two classical reliable communication protocols to leverage trusted nodes. We then propose DualRC, a novel algorithm that enables reliable communication in the hybrid authentication model by manipulating both dissemination paths and digital signatures, and leverages the possible presence of trusted nodes (e.g., network gateways) and trusted components (e.g., Intel SGX enclaves). We provide correctness verification algorithms to assess whether our algorithms implement reliable communication for all nodes on a given network.

Figures (4)

• Figure 1: The network shown in (a) contains 30 authenticated nodes with sufficient connectivity (3) for both SigFlood and DualRC to be correct when $f=1$. The network illustrated in (b) contains 10 authenticated nodes (in red), 10 non-authenticated nodes (in grey), 5 authenticated trusted nodes (in green), and 5 non-authenticated trusted nodes (in blue). DualRC is the only protocol that guarantees reliable communication in network (b).
• Figure 2: Taxonomy of processes.
• Figure 3: A network of 9 non-authenticated nodes (grey) that includes 3 trusted nodes (blue) where DolevU-T enforces reliable communication while DolevU does not.
• Figure 4: Example of a network where not forwarding signatures after delivering a message based on dissemination paths would prevent some nodes from authenticating it.

Theorems & Definitions (10)

• Definition 1
• Lemma 1
• Definition 1
• Definition 2
• Theorem 1
• Theorem 2: RC-Validity - untrusted $\leftrightarrow$ untrusted
• Theorem 3: RC-Validity - trusted $\leftrightarrow$ untrusted
• Theorem 4: RC-Validity - trusted $\leftrightarrow$ trusted
• Lemma 2
• Theorem 5