India’s quantum push faces a problem of proof

We do not usually ask what makes a digital transaction believable. It goes through, it settles, and the record stands.That depends on a simple idea: that what is verified today will remain verifiable tomorrow. In India, that idea carries unusual weight. Every UPI payment, every Aadhaar authentication, every digitally signed document and land record relies on it. It is what allows billions of transactions to move without friction, and what gives digital records their authority.But that expectation rests on methods that do not remain fixed.

As the old saying goes, satya sthir hota hai — truth endures. Indian thought has long drawn a distinction between satya (truth) and pramaan (proof). The difference now has practical consequences. Truth may remain. Proof depends on the methods used to establish it, and those methods change over time.

Nothing has stopped working. Transactions continue. Records still verify. Yet the durability we attribute to digital proof is less certain than it appears — and that changes how much weight these systems can carry as time passes.

A system built on proof at scale

India’s digital infrastructure now operates at a scale few countries have attempted. Retail digital payments crossed 22,000 crore transactions in 2024–25, with UPI accounting for the overwhelming majority, making it the largest real-time payment system globally. Aadhaar has issued over 1.3 billion identities, with authentication requests running into billions each month. Government platforms process vast volumes of service transactions every year, spanning taxation, welfare delivery, financial access, and property records.

At this level, transactions do not depend on familiarity or discretion. They depend on the ability to verify — instantly, repeatedly, and across distance.That changes the nature of trust. It is no longer carried only by institutions or intermediaries, but by the mechanisms that establish proof. Those mechanisms are cryptographic. They are mathematical, structured, and precise — but they are also tied to assumptions about what can and cannot be computed.

Much of the public conversation around quantum computing focuses on a dramatic future moment — when encryption breaks. That framing is misleading. Change in such systems

rarely arrives as a single event. Encryption weakens as better computational methods are developed, and what was once considered secure becomes progressively easier to compromise.

This matters because data does not disappear. It is stored, copied, archived — often for long periods, sometimes indefinitely. In cybersecurity, this is described as “harvest now, decrypt later”: information can be collected today and accessed in the future when stronger tools become available. This applies not only to sensitive state communication, but to financial transactions, identity systems, corporate records, and administrative databases.

There are already early indications of this transition. The United States has begun moving toward post-quantum cryptographic standards, anticipating future risks rather than waiting for failure. International institutions such as the Bank for International Settlements and the IMF have warned about the systemic

consequences of delayed transition, especially for systems that depend on long-term data integrity. India has committed `6,000 crore to the National Quantum Mission, with a focus on building technological capability.But the structural challenge lies elsewhere. It is not only about securing future systems.

It concerns the vast volume of data that has already been secured using older methods, and is expected to remain valid for years, sometimes decades.India’s existing digital records rest on cryptographic assumptions that were never designed to hold indefinitely.

When proof stops settling questions

At everyday scale, this is not visible. Payments go through. Documents are accepted. Systems respond as expected. The issue becomes visible when records are questioned — during disputes, audits, regulatory scrutiny, or judicial proceedings. India already has one of the largest volumes of civil litigation in the world, with land disputes forming a substantial share. At the same time, digital lending is expanding rapidly, with agreements created and stored entirely in electronic form. Courts and regulators are relying more frequently on digital evidence.

In such an environment, even a small shift in how proof is evaluated can have large effects.If a very small fraction of digital payment records are contested years later, the absolute number of disputes could run into the millions. Land records secured under current standards may become easier to challenge relative to newer ones. Identity-based authentication, when examined under evolving standards, may introduce similar complications in edge cases. But the issue is not the number of disputes. It is what happens to resolution.

India’s digital infrastructure is designed to settle questions quickly — whether a payment is complete, an identity is valid, or a document is authentic.

That ability to close matters is what allows these systems to operate at scale. Without it, every transaction would carry additional verification costs, slowing down systems that are built for speed.

If the strength of proof varies over time, that property begins to weaken. Records do not disappear, but they no longer settle questions in the same way. What was once treated as conclusive becomes open to re-examination. Older records become easier to challenge relative to newer ones, not because they are false, but because the methods behind them are no longer equally strong.

More transactions require reconciliation. Financial systems must account for a higher volume of contested outcomes. Legal processes take longer to reach closure, adding to already significant case backlogs. Administrative decisions —whether related to benefits, compliance, or enforcement — require additional layers of validation.

The cost of arriving at a final decision rises — not because systems fail, but because they cannot produce outcomes that remain final over time.

This introduces asymmetry. Two records that appear identical may not carry the same evidentiary strength, depending on when they were created and how they were secured.

Over time, this erodes the consistency with which decisions are made and accepted. That is not only a technical issue. It is a legal and administrative one too.

India’s policy approach to quantum technologies has so far been forward-looking. The focus has been on building capability, supporting research, and positioning the country within a global technological race. Regulatory frameworks have also strengthened cybersecurity practices across sectors.

But this challenge sits in a different category. Cybersecurity is concerned with protecting systems from attack, breach, or intrusion. This concerns the long-term credibility of records even in the absence of any attack.

There is also a limit to what policy can address later. Future systems can be upgraded. New cryptographic standards can be adopted. But existing records cannot be retroactively secured in the same way.

A transaction created today carries its assumptions forward into the future. As those assumptions weaken, so does the relative strength of that record.

Over time, this produces a layered system. Newer records, created under stronger and more resilient standards, retain greater integrity. Older ones, created under earlier assumptions, become more open to challenge.

India still has a window to respond before this becomes a source of systemic friction. Transition timelines for critical systems need to be clearly defined. Financial infrastructure, identity platforms, and governance databases cannot move in an uncoordinated manner. A phased approach is necessary, but it must also be time-bound.

High-risk records must be identified and prioritised. Not all data carries the same consequences. Financial contracts, land records, identity-linked systems, and regulatory filings require particular attention because they are most likely to be contested and have the highest downstream impact.

Legal and regulatory clarity is equally important. Courts and institutions will need to determine how digital evidence is evaluated as cryptographic standards evolve. Allowing these questions to be resolved only through litigation would introduce avoidable uncertainty.

India’s digital transformation has been built on the ability to verify at population scale.That achievement is substantial and of global importance. The next challenge is not expansion, but endurance.

Because the real test of any system is not whether it works in routine conditions. It is whether, years from now, it can still settle matters with the same confidence — and whether the proof it relies on continues to carry authority when it is most needed.

Author is a theoretical physicist at the University of North Carolina at Chapel Hill and a columnist on AI, infrastructure, and global systems; views are personal