Post-quantum cryptography: guarding encryption against quantum computers
Post-quantum cryptography (PQC) is encryption built on mathematical problems that neither conventional nor quantum computers are expected to solve quickly. The US National Institute of Standards and Technology finalised its first three PQC standards on 13 August 2024. A Task Force under India's National Quantum Mission wants critical sectors to begin migrating by 2027, its May 2026 report says.
Syllabus: Prelims · Science & Technology; GS3 · Science & Technology; GS3 · IT, Space, Biotech & IPR
In short
Post-quantum cryptography (PQC) is encryption built on mathematical problems that both conventional and quantum computers are expected to find hard, protecting today's data against tomorrow's machines.
Because harvested data can be decrypted later, India must migrate before a code-breaking quantum computer exists, pairing global standards with domestic testing and crypto agility.
Why it matters
Everyone who banks online, sends email or keeps medical records in digital form depends on encryption that a powerful quantum computer could break. The danger begins before such a machine exists: data stolen in encrypted form today can be stored and opened years later, so defence communications or health records that must stay secret for decades are already exposed. Replacing encryption is slow. NIST notes that a newly standardised algorithm has historically taken 10 to 20 years to reach every product and system. For India, the test is whether power grids, telecom networks, banks and government systems can change their cryptography before the threat arrives, using products tested at home.
Prelims pointers
- Post-quantum cryptography: mathematical algorithms that run on conventional computers and resist quantum attack; no quantum hardware is needed.
- Quantum cryptography: secures communication with the properties of quantum mechanics, not hard mathematics; quantum key distribution (QKD) is its best-known form.
- Shor's algorithm (1994): a quantum method to factor large numbers quickly; it is why RSA-type public-key encryption is at risk.
- Qubit: the basic unit of information in a quantum computer; it can act as 0 and 1 at the same time, and is easily disturbed.
- Key-encapsulation mechanism: lets two parties establish a shared secret key over a public channel; that key then runs symmetric-key encryption.
- Digital signature: detects unauthorised changes to data, authenticates the signatory and gives non-repudiation.
- National Quantum Mission: approved by the Union Cabinet in 2023; implemented by the Department of Science and Technology.
- Critical information infrastructure: defined in Section 70 of the Information Technology Act, 2000; the National Critical Information Infrastructure Protection Centre (NCIIPC) is the nodal agency.
Practise a UPSC-style question
With reference to post-quantum cryptography, consider the following statements:
1. It needs a quantum computer at both the sending and the receiving end of a communication.
2. Its algorithms rest on mathematical problems believed to be hard for both conventional and quantum computers.
Which of the statements given above is/are correct?
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Show the answer
Answer: (b) 2 only
1 is incorrect: post-quantum cryptography is a set of mathematical algorithms that run on conventional computers; no quantum hardware is needed. 2 is correct: its algorithms use problems such as lattice and hash problems that are expected to defeat conventional and quantum computers alike.
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