Video companion
After minutephysics on Shor's: what CISOs must know about RSA and ECC
minutephysics explains Shor's algorithm without requiring a physics degree. The gap for security leaders is translating period-finding into a concrete inventory of quantum-vulnerable algorithms.
What the video gets right
Shor's algorithm turns factoring large numbers — the hard problem behind RSA — into finding the period of a modular function. A cryptographically relevant quantum computer (CRQC) running Shor's breaks public-key crypto: RSA, Diffie-Hellman, and elliptic-curve variants (ECDH, ECDSA).
The video correctly notes that symmetric crypto like AES is not destroyed overnight; Grover's algorithm weakens it, which is why NIST recommends larger key sizes — but the urgent migration target is PKI and key exchange.
For background on period-finding, see the PennyLane period-finding demo.
What it does not cover
Explainers rarely answer operational questions: which certificates still use RSA-2048, which SaaS dependencies embed legacy algorithms, and who owns remediation. NIST's PQC overview describes the solution — standardized ML-KEM and ML-DSA — but inventory comes first.
Qtangl Assess tags quantum-vulnerable algorithms on external TLS and exports a CycloneDX CBOM — an inventory aid, not a formal attestation.
This quarter
- Watch the embedded video, then skim NIST's post-quantum cryptography explainer.
- Run a baseline scan on external TLS — list RSA, ECDSA, and ECDH dependencies.
- Tag findings by data shelf-life tier for Mosca HNDL scoring on the HNDL hub.
Continue on the Q-Day hub: What is Q-Day? guide
References & further reading
Authoritative primary sources cited in this article. Summaries are our own — follow links for full context.
Last verified 2026-06-21
- How Quantum Computers Break Encryption | Shor's Algorithm Explainedminutephysics (YouTube) · 2019Accessible explainer on Shor's algorithm, period-finding, and why RSA breaks on a large quantum computer.
- Shor's Algorithm: A Quantum Threat to Modern CryptographyPostQuantum.com · 2024Written explainer for security professionals — RSA, ECC, Shor's steps, and PQC migration strategies.
- What Is Post-Quantum Cryptography?NIST · 2024Official overview of NIST's PQC project, finalized standards, and the harvest-now-decrypt-later threat model.
- Period finding: A problem at the heart of quantum computingPennyLane · 2024Interactive demo explaining period-finding — the core of Shor's algorithm.
See your exposure with evidence
Run a live PQC inventory scan, export a CBOM, and verify signed reports independently.