"From ‘quantum-enhanced’ to ‘quantum-safe’: Why banks are preparing in advance for the new big threat"
Qubit
the basic unit of quantum computing that can hold a mix of 0 and 1 at once
Superposition
a quantum property where a qubit exists in multiple states simultaneously
Modern digital security uses public-key cryptography. This means a public key locks data and a private key unlocks it. Systems like RSA (Rivest-Shamir-Adleman) and elliptic-curve cryptography protect banking transactions, UPI payments, and digital signatures. These systems are secure because classical computers cannot easily solve certain math problems in a reasonable time. A qubit is the basic unit of quantum computing. A classical bit is only 0 or 1. A qubit can exist in a mix of 0 and 1 at the same time. This property is called superposition. Quantum computers also use entanglement. Qubits become linked so that the state of one affects another instantly.
These properties let quantum computers solve some problems far faster than ordinary computers. One such problem is breaking RSA and elliptic-curve encryption. This depends on factoring huge numbers or solving discrete-logarithm problems. A powerful enough quantum computer could do this quickly. Classical computers would take an extremely long time. This has led to global efforts to prepare in advance. The DST Task Force (2026) recommends that India urgently migrate its digital infrastructure to post-quantum cryptography (PQC). PQC is a set of encryption methods designed to resist attacks even from quantum computers. The report names the point when a quantum computer becomes capable enough to break today's encryption as 'Q-day'. Experts estimate it could arrive between 2029 and the mid-2030s.
India's financial ecosystem depends on UPI, Aadhaar, RTGS, and NEFT. All of these rely heavily on cryptographic systems for authentication, secure communication, and digital signatures. This is why the quantum threat is not a distant science topic. It is a live concern for financial regulators. They must plan for a transition that could take years to complete. Old, deeply embedded systems make this transition slow.
Quantum algorithms work by manipulating qubits. Correct answers become more likely and wrong answers less likely. This uses superposition and entanglement together. The most relevant algorithm for cryptography is Shor's algorithm. Shor's algorithm allows a sufficiently powerful quantum computer to factor large numbers and solve discrete-logarithm problems far faster than any classical computer. RSA and elliptic-curve systems rely on exactly these problems being hard to solve. A cryptographically relevant quantum computer could break them.
This is why experts describe a threat called Harvest Now, Decrypt Later (HNDL). An attacker intercepts and stores encrypted data today, planning to decrypt it later once quantum computers become powerful enough. This makes any data that must stay confidential for many years vulnerable. Financial records, defence communications, and identity data are all at risk. This risk exists even before quantum computers actually arrive. …
With reference to modern cryptographic systems, consider the following statements:
1.RSA encryption's security depends on the difficulty of factoring very large integers.
2.Elliptic-curve cryptography's security depends on the difficulty of solving discrete-logarithm problems.
3.The 'Harvest Now, Decrypt Later' threat involves attackers instantly decrypting data using classical computers alone.
Which of the statements given above is/are correct?
Consider the following statements regarding quantum computing:
1.A qubit can exist in a superposition of both 0 and 1 states simultaneously.
2.Entanglement refers to a qubit's ability to switch between classical bit and qubit states.
3.Shor's algorithm enables efficient factorisation of large integers on a sufficiently powerful quantum computer.
How many of the above statements are correct?
Consider the following statements:
1.Post-quantum cryptography (PQC) algorithms are designed to run on classical computers while resisting quantum attacks.
2.Quantum Key Distribution (QKD) relies on the physical properties of quantum particles to securely exchange encryption keys.
3.QKD is generally easier to scale across large networks than software-based PQC.
Which of the statements given above is/are correct?
Match List-I (Institution/Body) with List-II (Cybersecurity/Quantum-related initiative) and select the correct answer using the code given below:
List-I
A.Reserve Bank of India (RBI)
B.Securities and Exchange Board of India (SEBI)
C.US National Institute of Standards and Technology (NIST)
D.DST Task Force (India)
List-II
1.Finalised three post-quantum cryptography standards
2.Recommended India's urgent migration to post-quantum cryptography
3.Issued a cybersecurity and technology-resilience framework for commercial banks
4.Introduced an IT Resilience Index for market infrastructure institutions
'Q-day', the point at which a quantum computer may become capable of breaking widely used public-key encryption, is estimated by experts to potentially arrive:
Want the full note, Prelims Facts & MCQ answers?
Create a free account — takes less than a minute.
Create free account