Quantum computers could eventually undermine some of the encryption that protects the global financial system, putting everything from payment-card transactions and bank transfers to digital signatures and financial records at risk.
In an analysis by IBM, the company writes that the threat does not mean quantum computers will suddenly empty bank accounts or make electronic payments unusable. Today’s quantum machines remain far from capable of breaking the cryptography used by major financial networks. The concern is that sufficiently powerful quantum computers could eventually defeat widely used forms of public-key cryptography, particularly RSA and elliptic curve cryptography, or ECC.
This risk has been widely discussed in industry research, including IBM’s analysis of quantum-safe cryptography, which highlights how advances in quantum computing could eventually render today’s asymmetric encryption vulnerable and why organizations should begin preparing migration strategies now.
That possibility has started a long transition toward post-quantum cryptography, or PQC — encryption and digital-signature methods designed to resist attacks from both conventional and quantum computers.
The National Institute of Standards and Technology finalized its first three major PQC standards in 2024 and has urged organizations to begin migrating. NIST’s transition plans call for quantum-vulnerable algorithms to be deprecated and ultimately removed from its standards by 2035, with higher-risk systems moving sooner.
IBM has similarly emphasized in its post-quantum cryptography guidance that organizations should begin planning for “crypto-agility” now, since cryptographic transitions in complex environments can take many years to complete safely.
For the financial industry, however, replacing an algorithm is only part of the problem. Cryptography is embedded throughout banks, payment networks, clearing systems, ATMs, point-of-sale terminals and the communications links connecting them. The Financial Services Information Sharing and Analysis Center, or FS-ISAC, has warned that the number of systems and dependencies across financial services makes cryptographic migration increasingly difficult.
IBM’s research on enterprise cryptographic modernization similarly notes that large organizations often lack full visibility into where encryption is used, making it difficult to identify all systems that must be upgraded.
The result is an unusual cybersecurity problem because while the threat of quantum computers may still be years away, but preparing for it could also take years.
Why Quantum Computers Pose a Threat to Financial Security
Much of modern financial security depends on mathematical problems that are extremely difficult for conventional computers to solve.
RSA, for example, derives its security from the difficulty of factoring very large numbers. ECC relies on a different mathematical problem involving elliptic curves. These systems help establish secure communications and verify digital identities across the internet and financial networks.
A sufficiently large, fault-tolerant quantum computer could change that.
Shor’s algorithm, proposed by mathematician Peter Shor in 1994, demonstrated that a quantum computer could theoretically solve the mathematical problems behind RSA and ECC much more efficiently than conventional machines.
IBM’s quantum security research has repeatedly highlighted Shor’s algorithm as the central reason public-key cryptography is considered vulnerable in a future fault-tolerant quantum era.
No existing quantum computer is known to be capable of doing this against cryptographic keys used in real financial systems. Such an attack would require a machine substantially larger and more reliable than today’s systems, including effective quantum error correction.
The uncertainty surrounding when such a machine might arrive makes planning difficult. But financial institutions cannot necessarily wait for a definitive date.
One reason is the so-called “harvest now, decrypt later” threat. An attacker can collect encrypted information today and store it. If a sufficiently capable quantum computer becomes available later, the attacker could attempt to decrypt the previously stolen material.
IBM has specifically warned about this scenario in its quantum-safe security guidance, noting that sensitive data with long-term value is especially at risk because it may remain useful long after it is intercepted.
The risk depends heavily on how long the information remains valuable. A one-time piece of short-lived information may have little value years later. Customer identities, financial histories, account information, confidential business records and some authentication data can have much longer useful lives.
That makes the financial sector particularly sensitive to the timeline.
Which Payment Systems Are Vulnerable to Quantum Computers?
The quantum threat is not limited to credit cards or online banking. Public-key cryptography is used throughout the infrastructure connecting financial institutions. IBM identifies the following:
Payment card networks: Credit and debit card ecosystems use cryptography across card provisioning, authentication, transaction routing, authorization and communications between merchants, processors, acquiring banks and issuing banks. FS-ISAC has specifically identified payment-card infrastructure as an area requiring preparation for post-quantum migration.
IBM’s financial services security research similarly notes that payment ecosystems are especially complex because they rely on many interconnected parties, each of which may need to upgrade cryptographic systems in coordination.
Online and mobile banking: Secure connections between customers and financial institutions rely on cryptographic protocols to establish encrypted sessions and authenticate servers. Quantum-vulnerable public-key algorithms can appear within these communications even when the underlying transaction data is protected with other forms of encryption.
Real-time payment systems: Instant-payment networks depend on secure communications and authentication among banks, processors and payment operators. Cryptographic weaknesses could affect the trust mechanisms used to establish connections or verify participants.
Real-time gross settlement systems: RTGS systems are used by central banks and major financial institutions to settle large-value transactions. Because these systems sit near the core of national financial infrastructure, their security and authentication mechanisms are particularly important.
Automated clearinghouse networks: ACH systems process large volumes of electronic payments, including payroll deposits, bill payments and bank-to-bank transfers. Cryptography can protect communications, authenticate participants and help secure infrastructure surrounding these transactions.
Cross-border payment networks: International payments pass through interconnected banks, payment networks, correspondent banks and service providers. That creates an additional migration problem because institutions in different countries may adopt new cryptographic standards at different speeds.
ATMs and point-of-sale systems: FS-ISAC’s payment-card guidance identifies ATM and POS environments among the use cases that need to be considered in post-quantum planning. These systems connect physical devices with acquiring institutions and backend processing infrastructure.
Central bank digital currencies: If central banks deploy wholesale or retail digital currencies at scale, those systems will also depend on cryptographic mechanisms for authentication, transaction security and other functions.
Stablecoins and tokenized financial assets: Digital-asset platforms frequently depend heavily on public-key cryptography and digital signatures. In some systems, control of an asset is directly linked to possession of a private cryptographic key, making long-term cryptographic security especially important.
The vulnerability does not mean every component of these systems becomes insecure when a powerful quantum computer arrives.
Quantum computing primarily threatens particular forms of public-key cryptography. Symmetric encryption — in which the same secret key is used to encrypt and decrypt information — is affected differently and can generally be strengthened by using sufficiently large keys.
IBM’s cryptographic guidance also emphasizes that symmetric algorithms are far less vulnerable to quantum attacks, though they may require larger key sizes to maintain equivalent security levels.
That distinction matters because financial systems use multiple layers of cryptography. A bank may need to replace some algorithms while retaining or strengthening others.
Why Migrating the Financial System Will Take Time
One of the largest obstacles is finding the vulnerable cryptography in the first place.
Large financial institutions can operate thousands of applications across cloud systems, data centers, networks, employee devices and decades-old infrastructure. Cryptographic algorithms can also be buried inside third-party software and hardware.
IBM has highlighted this challenge in its enterprise security research, noting that many organizations lack a complete inventory of where cryptographic functions are used, which makes migration planning significantly more complex.
A bank therefore needs what is essentially a cryptographic inventory, which is a map showing where encryption, digital signatures, certificates and cryptographic keys are being used.
NIST’s post-quantum migration work emphasizes this type of cryptographic visibility as an early step. Organizations need to determine which systems contain quantum-vulnerable algorithms before they can decide what should be replaced first.
Financial institutions face an additional problem because they do not operate independently.
A payment transaction may involve a merchant, payment gateway, processor, card network and multiple banks. A cross-border transaction can add correspondent banks and other intermediaries.
Changing cryptography at one organization can therefore affect other participants.
FS-ISAC has called for coordinated international migration planning, arguing that the interconnected nature of financial services makes synchronization important. One institution cannot become fully quantum-safe if critical counterparties still require vulnerable cryptographic protocols.
IBM’s research similarly stresses the importance of ecosystem-wide coordination, since cryptographic upgrades must be compatible across vendors, partners and infrastructure providers.
Benefits of Post-Quantum Migration Beyond the Quantum Threat
Preparing for quantum computing can also address security problems that already exist.
One of the most important is cryptographic visibility. Institutions that inventory their cryptographic assets gain a clearer picture of where keys, certificates and encryption algorithms are deployed. That can expose outdated software, weak algorithms, expired certificates and poorly managed keys before quantum computing becomes relevant.
IBM has identified cryptographic discovery as a foundational step in building quantum-safe systems, since organizations cannot protect what they cannot see.
Another benefit is crypto-agility.
Crypto-agility means designing systems so that cryptographic algorithms can be replaced without rebuilding the surrounding infrastructure. Rather than treating the transition to PQC as a single upgrade, organizations build a repeatable process for changing cryptography when standards or threats change.
IBM has strongly advocated for crypto-agility as a core design principle for quantum-safe architectures, noting that it reduces long-term risk and simplifies future cryptographic transitions.
That capability has value even if large-scale quantum computers arrive later than expected. Cryptographic algorithms can become vulnerable for reasons unrelated to quantum computing, and security standards evolve over time.
Crypto-agility can also reduce the cost and disruption of future migrations. FS-ISAC has argued that previous cryptographic transitions have grown more complicated as financial systems have become increasingly interconnected.
There are potential regulatory benefits as well. Organizations that understand their cryptographic infrastructure may be better positioned to demonstrate to regulators that sensitive information is properly protected and that security risks are being managed systematically.
Migration can also improve operational resilience. Centralized management of cryptographic assets can give security teams greater visibility into certificates, keys and algorithms, potentially making it easier to identify failures and respond when cryptographic components need replacement.
There is also a business continuity benefit. Financial institutions depend on secure communications to conduct routine operations. Building systems capable of changing cryptographic methods with minimal downtime can reduce the chance that a future security flaw forces a rushed or disruptive replacement.
Finally, post-quantum preparation can improve coordination with suppliers and partners. Banks conducting cryptographic inventories will often discover dependencies on vendors, cloud providers, payment processors and other outside organizations. Identifying those dependencies early can help institutions determine which suppliers are prepared for PQC and which could become migration bottlenecks.
The Post-Quantum Financial System Is Already Taking Shape
NIST has standardized three principal post-quantum algorithms: ML-KEM for establishing shared encryption keys, and ML-DSA and SLH-DSA for digital signatures. The agency continues to evaluate additional algorithms as potential alternatives and backups.
IBM has also contributed to the development and implementation of post-quantum cryptography, including early support for quantum-safe algorithms and integration work across enterprise systems, helping accelerate real-world adoption of NIST standards.
These algorithms do not require quantum computers. They are designed to run on conventional computing systems while resisting attacks from both conventional and future quantum machines.
Financial institutions therefore do not need to wait for quantum hardware before deploying quantum-resistant security.
The larger challenge is determining where to deploy it first.
Systems protecting information that must remain confidential for many years may warrant earlier attention because of harvest-now-decrypt-later attacks. Critical payment infrastructure and systems that are difficult to upgrade may also require long lead times.
At the same time, migration must be tested carefully. Financial systems prioritize reliability, and introducing new cryptographic software can affect performance, compatibility and communications with other institutions.
The financial sector’s vulnerability to quantum computing is therefore less a story about an imminent quantum attack than about infrastructure planning.
No one knows exactly when a quantum computer capable of breaking today’s public-key cryptography will be built. It could take longer than aggressive forecasts suggest.
But financial institutions do know that cryptography is woven deeply into the systems that move and protect money.
Finding that cryptography, replacing vulnerable algorithms and making financial infrastructure easier to update could take years. And many of those changes improve security even if the quantum threat develops more slowly than expected.
That makes post-quantum migration unusual among cybersecurity preparations. Banks do not have to predict the exact arrival of a powerful quantum computer for the investment to have value. The same work needed to prepare for tomorrow’s quantum threat can make the financial system easier to secure today.
