Almost every secure message sent today, from a bank transfer to a WhatsApp chat, relies on mathematical problems that ordinary computers would take millions of years to solve. A sufficiently powerful quantum computer could solve some of them in hours. That machine does not exist yet, and experts disagree about when it will. But security agencies, banks and telecom operators are no longer treating the threat as distant.
The reason is simple. Data encrypted today can be recorded today and decrypted later. Diplomatic cables, medical records, trade secrets and defence communications often need to stay confidential for decades. If an adversary is quietly storing encrypted traffic now, the clock on that data has already started.
A new generation of locks
The response is post-quantum cryptography: new algorithms built on mathematical problems that are believed to be hard for both classical and quantum computers. After years of public competition and analysis, international standards bodies have published the first set of these algorithms, and software vendors have begun building them into browsers, operating systems and messaging apps.
For India, the question is not whether to adopt the new standards but how quickly and in what order. Replacing cryptography across a country's digital infrastructure is a vast undertaking. It touches payment networks, identity systems, government portals, power grids and the billions of devices that connect to them.
“Migration is not a software update. It is an inventory problem first: you cannot replace what you do not know you are using.” — Dr. Raghav Iyer, cryptography researcher (fictional, for this demo)
Starting with an inventory
Security teams we spoke to describe the first step as unglamorous but essential: finding every place cryptography is used. That includes obvious systems such as web servers and VPNs, but also embedded devices, legacy applications and third-party software whose internals are poorly documented. Large organisations often discover thousands of instances they did not know about.
Once the inventory exists, teams can prioritise. Systems that protect long-lived secrets come first. So do systems that are hard to update later, such as hardware with a lifespan of ten or fifteen years. Short-lived data that loses value quickly can wait.
Hybrid approaches
Many organisations are adopting hybrid schemes in the meantime, combining a traditional algorithm with a post-quantum one so that a message stays secure as long as either holds. This hedges against the possibility that one of the new algorithms turns out to have a weakness, which has happened before with candidates in the standards process.
The role of quantum key distribution
Alongside new algorithms, India has invested in quantum key distribution, which uses the physics of single photons to share encryption keys in a way that reveals any eavesdropping. Researchers have demonstrated links over fibre between cities and over free space between buildings, and longer-term plans include satellite links.
Quantum key distribution is not a replacement for post-quantum algorithms. It requires dedicated hardware, works over limited distances without trusted relays and is best suited to high-value links between fixed sites. But for certain government and defence networks, it offers an additional layer of assurance.
Industry and skills
The migration is creating demand for skills that are in short supply worldwide: engineers who understand both cryptography and the messy reality of production systems. Indian universities and research institutes have started specialised courses, and several startups are building tools to scan codebases for vulnerable cryptography and help manage the transition.
Hardware is another opportunity. Smart cards, payment terminals and secure chips will all need new designs that can run post-quantum algorithms efficiently. Indian companies that move early could supply both domestic and international markets.
Payments and identity
India's digital payment and identity systems are among the largest in the world, and their scale makes migration both urgent and delicate. A change to the cryptography behind a payment network must work on every bank's systems, every merchant's terminal and every phone app at the same time, or transactions fail. Planners describe staged rollouts, with old and new algorithms running side by side for years.
Devices already in people's pockets add another layer of difficulty. Phones and cards that cannot be updated will eventually need to be replaced, and that replacement cycle has to be planned well before the deadline arrives.
Racing a moving target
The uncomfortable truth is that nobody knows exactly how much time remains. Progress in quantum hardware is real but uneven, and estimates of when a cryptographically relevant machine might appear range from a decade to several. What is clear is that a large migration takes years, and starting late is far more dangerous than starting early.
For a country that has built so much of its economy on digital public infrastructure, the stakes are high. The new locks are available. The task now is to fit them, door by door, before anyone arrives with the key.