The argument for starting now, to address the threat that quantum computers will pose to existing security systems, is based on the following considerations: 1. cryptographic technologies are integrated into most of the digital products commonly used by organizations to run their daily operations; ^[https://www.cyber.gc.ca/en/guidance/using-encryption-keep-your-sensitive-data-secure-itsap40016] 2. some of the applications and systems used within energy, transportation, finance and government infrastructures have product lifetimes of 15 - 30 years, and even longer requirements for data protection and privacy; 3. fault-tolerant quantum computers, capable of breaking existing asymmetric encryption algorithms and cryptographic systems (e.g., public-key infrastructures), are widely expected to be available within the above timeline (e.g., by 2035); ^[https://www.whitehouse.gov/briefing-room/statements-releases/2022/05/04/national-security-memorandum-on-promoting-united-states-leadership-in-quantum-computing-while-mitigating-risks-to-vulnerable-cryptographic-systems/] 4. the time needed to migrate installed cryptographic technologies (e.g., SHA1) to newer standards can take many years; ^[https://www.computerworld.com/article/1680543/the-sha1-hash-function-is-now-completely-unsafe.html] 5. the number of cryptographic systems that organizations will need to migrate to use new “quantum-safe” cryptography will be large; and 6. most organizations have no clear view of the cryptographic technologies used by their existing Information Management (IM), Information Technology (IT) and Operational Technology (OT) systems; this will make it difficult to discover and then prioritize the systems to be upgraded to post-quantum cryptography. ^[https://www.dhs.gov/sites/default/files/publications/post_quantum_cryptography_faq_3_seals_october_2021_508.pdf] Migrating an organisation’s cryptographic systems to PQC will require significant effort. Organizations should begin planning now given that: - the effort and time needed (e.g., to investigate, analyse, plan, procure, migrate, and validate new PQC) will not be small, and it will be different for every organization; and - the amount of time remaining (until threat actors can access sufficiently powerful quantum computers to break existing cryptography) will decrease every day.