The new DST Task Force report on making India’s digital ecosystems quantum-safe is a product of contemplating a threat that is both long-term and urgent. Today, public-key cryptography underpins online identity protection and secure communications. Its protective ability rests on mathematical problems that conventional computers cannot solve efficiently; thus, the information is ‘hidden’ behind a lock whose key is the solution to such a problem. However, a sufficiently capable quantum computer could use, say, Shor’s algorithm to open this lock in minutes or hours. Symmetric cryptography, such as AES encryption, is less threatened by the advent of quantum computers but the existential exposure is nonetheless concentrated in public-key infrastructure, which secures everything from HTTPS to telecommunication networks. The shorter-term problem is the possibility of a bad actor harvesting encrypted data today and decrypting them later using quantum computers. Post-quantum cryptography (PQC) is software that can run on conventional computers but with the added benefit of resisting attacks from quantum computers. The DST report recommends three post-quantum standards finalised in 2024 to plan India’s efforts on the post-quantum effort and that it begin migrating to this architecture. This prudent advice must be followed, especially vis-à-vis critical infrastructure, financial services, power grids, and defence. The migration must continue even if “Q-day” — when quantum computers practically endanger public-key cryptography — is pushed back from the report’s expected 2029. Indeed, experts disagree on this point, although the mainstream view is that both “Q-day” and migration will take at least a decade. Cryptography is in practice a set of dependencies often spread across — within, say, a ministry — databases, legacy hardware, vendor software, authentication protocols, and control systems. Thus, the challenges of the sprawling organisational transition must not be underestimated. Moreover, since advanced AI can autonomously compromise the software layer today and quantum