A Cryptographic Analysis of Google’s PSP and Falcon Channel Protocols

Google introduced the Falcon channel protocol for efficient data exchange over unreliable networks in its data centers. The protocol augments Google’s basic PSP channel protocol for secure transportation through mechanisms like replay protection and congestion control and provides request-response-based interfaces for upper-layer protocols. Falcon has recently been opened to the public as part of the Open Compute Project, describing the design and choices as Falcon Transport Protocol Specification. We analyze Falcon here in the recently introduced security model of Fischlin et al. (Journal of Cryptology, 2024) for channel protocols, which is particularly applicable to unreliable networks and security properties like replay protection. In passing, we also investigate the security of PSP on which Falcon is based. Our results indicate that PSP and Falcon provide adequate security, albeit our studies also reveal several security-related ambiguities in the specification.