Challenge
A coalition of financial institutions – including several major banks and the operator of a central interbank payment network – came together to confront a shared concern: how would quantum computing threats impact the security of interbank payment and settlement flows? These flows encompass everything from a customer initiating a wire transfer at their local bank, to that bank’s internal processing systems, to the messaging between banks over networks like SWIFT, and finally to the central bank’s real-time gross settlement (RTGS) system where funds are ultimately exchanged. This end-to-end chain is the backbone of the financial system, and it relies on multiple layers of cryptography and trust. The challenge was to map out all the points in this complex chain where cryptography is used (or data is vulnerable), determine which of those might be broken or weakened by a future quantum adversary, and gauge the systemic risk – if one piece was compromised, could it undermine the entire payment system?
The task was daunting due to the heterogeneity of systems and stakeholders. Each bank had its own applications and protocols for customer transactions and internal processing. The interbank messaging (like SWIFT) introduced a common standard, but one that was globally distributed and outside any single bank’s control. The central infrastructure (like a central bank’s RTGS platform) had its own legacy systems and security measures. Coordination between these players on cybersecurity is not routine, so tackling a future risk that doesn’t neatly fall in any one organization’s responsibility required a collaborative, impartial effort. Moreover, there was a need to anticipate not only direct attacks (like breaking encryption on a payment message) but subtler impacts, such as a malicious actor recording large volumes of encrypted traffic now to decrypt years later, potentially revealing sensitive transaction patterns or keys. The group needed a clear roadmap of where to upgrade to post-quantum cryptography (PQC), how to ensure those upgrades were done consistently across the network, and how to align with external entities (like the SWIFT organization and central banks) so that no link in the chain remained weak.
How Applied Quantum Helped
Our team served as the independent examiner and facilitator for this quantum-risk assessment of the interbank payment ecosystem. We proceeded step by step to create a full cryptographic risk map and set of recommendations:
End-to-End Cryptography Mapping: We worked with security architects from each participating bank and the central infrastructure operator to diagram the entire payment flow and enumerate all cryptographic controls in place. This spanned customer-facing layers (e.g., the TLS encryption in online banking or mobile apps through which payments are initiated, and the 2FA or digital signature schemes used to authorize transactions) through the banks’ internal systems (encrypted databases, service buses, HSMs managing cryptographic keys, etc.), the interbank messaging layer (e.g., SWIFT FIN messages which are authenticated and protected by a community-wide PKI and HSM-based signing at each institution), and the central settlement layer (where central banks often use secure communication channels and cryptographic message authentication to settle net positions). For each segment, we documented the specific algorithms and key lengths in use, key management processes (such as key rotation schedules for SWIFT or certificate management practices at the central bank interface,), and the lifespan of the data protected. This exercise resulted in a detailed map of dependencies. This highlighted, for example, that a single compromised certificate authority could affect multiple banks, and that certain payment records remain sensitive for decades in archives.
Identification of Long-Lived Data and Choke Points: Using the map, we analyzed where the system was most susceptible to quantum threats. One focus was on long-lived data: information that, if captured today, would still be sensitive by the time a quantum computer might exist. This included things like archival payment logs that contain private customer or transaction details (which could be targeted by economic espionage), or the secret keys that protect those archives. For example, we discovered some interbank communication logs were stored encrypted but kept for decades – meaning if their classical encryption were broken in the future, decades of historical transaction data could be exposed. Another area was the systemic choke points: components that all participants rely on, meaning a weakness there is an issue for everyone. The SWIFT network emerged as a key example – its cryptographic authentication underpins trust between banks. We noted that if SWIFT’s current authentication algorithms were rendered insecure by quantum attacks, an adversary could potentially forge or alter payment instructions at scale. Likewise, the digital signature schemes used in the central RTGS system (often classical RSA/ECC) would need timely replacement with quantum-safe alternatives. We highlighted these as critical upgrade targets; they were the “weakest links” that could compromise the entire chain if not addressed, even if individual banks secured their own systems.
PQC Adoption and Crypto-Agility Recommendations: Based on the findings, we crafted a set of coordinated recommendations. We advised that all parties begin adopting post-quantum cryptography in a phased manner. For instance, we advised the banks to plan upgrades of customer-facing channel encryption to hybrid post-quantum modes (combining classical and PQC algorithms) once standards are finalized, protecting data in transit from future decryption. We also urged the consortium to work with SWIFT on piloting quantum-safe message authentication within the network, to ensure new PQC keys or signatures can integrate into existing messaging protocols. For the central RTGS operator, we suggested scheduling a project to upgrade its messaging and signing systems to quantum-safe algorithms (aligned with their normal tech refresh cycle) well before large-scale quantum computers are expected to arrive. We emphasized crypto-agility in all these measures: systems should support multiple algorithms concurrently during the transition (allowing a safe fallback) and use modular cryptographic components so that swapping out an algorithm in the future wouldn’t require major redesign.
Crucially, we recommended strong governance and coordination. We proposed a joint task force including the banks, the payment network operator (SWIFT), and central bank representatives to keep everyone’s plans in sync. We also provided tailored playbooks for each stakeholder – outlining steps for individual banks to inventory and upgrade their systems, guidance for the network operator to introduce PQC compatibility (given it must interoperate with all parties), and talking points for engaging regulators to support a smooth, industry-wide transition.
Outcome
The collaborative assessment gave the banking coalition a unified understanding of where quantum threats intersect with their interbank payment processes. This was an unprecedented level of detail – for the first time, many of the banks could see not just their own vulnerabilities, but how a weakness in one part of the system (even outside their direct control) could impact everyone. The group produced a joint quantum-risk report that mapped out the cryptographic weak points and prioritized them. This report was shared with industry bodies and SWIFT as a call to action. As a direct result, SWIFT established a quantum security working group (including consortium members) to explore and pilot PQC implementations within its network.
At the individual bank level, the findings accelerated internal projects. Each bank took the cryptographic mapping we provided for their systems and initiated upgrades or plans in line with our recommendations. For instance, one of the major banks brought forward a planned upgrade of its HSM infrastructure (which manages signing of payment instructions) to ensure it could support new PQC algorithms. Several banks began testing hybrid TLS configurations in their labs, preparing for a future update to customer-facing channels. Importantly, having gone through this process together, the banks remained in sync – no one wanted to be the weak link holding up the group.
The central payment infrastructure operator (the central bank) leveraged our assessment to secure funding to overhaul its RTGS platform with quantum-safe security – using our analysis as evidence that investing now (rather than waiting a decade) was crucial for financial stability.
Additionally, this collective approach solved the coordination problem: knowing everyone was moving together made each bank more willing to invest early. The recommended task force was established and began meeting regularly to share progress and agree on common targets (such as a date by which all institutions would support a chosen PQC standard for interbank messages). This gives assurance that no bank will be left vulnerable by another’s inaction.
In essence, our engagement turned an abstract threat into a concrete, actionable plan for the interbank payment community. It fostered collaboration between competitive institutions in the face of a common risk, and laid the groundwork for a smoother transition to quantum-safe security across an entire sector. By proactively addressing the issue, the banks and payment operator not only reduce future risk but also demonstrate to regulators and customers that the resilience and integrity of the financial system will be maintained, even in the quantum computing era.
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