The threat from Cryptographically Relevant Quantum Computers (CRQCs) has evolved from a distant hypothesis into an urgent security reality. This article asserts that the true deadline for Post-Quantum Cryptography (PQC) migration is now, driven by the “Harvest Now, Decrypt Later” (HNDL) threat model—where adversaries exfiltrate encrypted, long-lived data today, anticipating its future decryption by quantum means. To counter this emerging risk, organizations must adopt the Crypto-Agility Mandate, a proactive architectural strategy designed to safeguard systems before CRQCs reach operational maturity. The proposed roadmap focuses on four immediate imperatives: conducting a comprehensive Cryptographic Bill of Materials (CBOM) to map existing encryption dependencies; deploying Hybrid Cryptography to bridge classical and quantum-safe algorithms; automating Certificate Lifecycle Management (CLM) to manage escalating cryptographic complexity; and enforcing PQC compliance across the digital supply chain. By embedding crypto-agility today, enterprises can fortify their digital infrastructure and ensure long-term resilience in the approaching quantum era.
Keywords: Crypto-Agility, Cryptographically Relevant Quantum Computers (CRQC), Harvest Now Decrypt Later (HNDL), Post-Quantum Cryptography (PQC), Quantum Security
