Quantum Computing Risks and Mitigations for Maritime Autonomous Surface Ships: A Structured Risk Assessment

A maritime autonomous surface ship (MASS) operates with reduced or absent crew and depends on cryptography to authenticate the commands, software updates, and position data that keep it under control, and on satellite positioning to navigate. Quantum computing changes this risk picture in two opposite directions that this study keeps separate. As a threat, a cryptographically relevant quantum computer would break the public-key cryptography that authenticates remote-control commands, code-signing signatures, and position exchanges, and adversaries can harvest long-lived encrypted data now for later decryption. As a contributor to mitigation, quantum sensing offers positioning that does not rely on satellite signals, addressing the distinct problem of positioning denial. No prior work has named the specific quantum-related risks to such a vessel, rated them under a degree of autonomy, and paired each with a mitigation and a residual-risk estimate; this study provides that assessment. Following the International Maritime Organization Formal Safety Assessment style and the ISO 31000 process, it identifies eight risks, rates likelihood and consequence on defined qualitative scales that represent structured expert judgement (with consequence conditioned on autonomy), applies bow-tie analysis to the highest-rated risks, and adds a sensitivity analysis, uncertainty ranges, and an illustrative cyber-physical propagation model. Positioning denial and command-link forgery rate highest; the ranking is robust to the threshold choices tested, with the autonomy conditioning the most influential assumption. Migration to post-quantum cryptography combined with a non-satellite positioning fallback reduces residual risk most. The register is offered to operators, classification societies, and flag administrations as a basis for planning and for expert elicitation, with its ratings stated as judgement open to revision.