Post-Quantum Cryptography
Post-quantum cryptography is public-key cryptography designed to resist attacks from both conventional and future large quantum computers. It replaces quantum-vulnerable key establishment and digital signatures while continuing to run on ordinary computers and networks.
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Intro
Post-Quantum Cryptography
Post-quantum cryptography, or PQC, is public-key cryptography designed around mathematical problems that are believed to resist attacks by both conventional and large quantum computers. It runs on conventional hardware. It is different from quantum key distribution, which depends on quantum communication equipment.
The transition matters because a sufficiently capable quantum computer running Shor's algorithm could solve the factoring and discrete-logarithm problems behind RSA, finite-field Diffie–Hellman, elliptic-curve Diffie–Hellman, DSA, and ECDSA. Those systems provide key establishment, authentication, and signatures across TLS, virtual private networks, software updates, certificates, messaging, and identity systems. Grover's algorithm gives a smaller, quadratic speedup against brute-force search. Symmetric encryption and hashing therefore need adequate key and output sizes, but they do not require the same wholesale replacement as vulnerable public-key systems.
No cryptographically relevant quantum computer is known to exist. Migration still begins before one does. An attacker can record encrypted traffic now and attempt to decrypt it later. Long-lived secrets face this harvest-now-decrypt-later risk as soon as their required confidentiality period extends beyond the expected migration and quantum-computer timelines.
Two jobs, three standards
PQC does not provide one universal replacement algorithm. Public-key cryptography has two main jobs, and NIST's first standards separate them.
ML-KEM, specified by FIPS 203, is a key-encapsulation mechanism. One party generates an encapsulation key and a decapsulation key. Another party uses the encapsulation key to produce a ciphertext and a shared secret. The holder of the decapsulation key recovers the same shared secret from that ciphertext. A protocol then feeds the shared secret into symmetric-key derivation and uses the resulting keys for encryption and authentication. ML-KEM does not encrypt an application message directly and does not authenticate the peer by itself.
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Sources
- https://www.nist.gov/cybersecurity-and-privacy/what-post-quantum-cryptography
Supports
- PQC definition, conventional-hardware use, quantum threat, and distinction from quantum cryptography
- Public-key replacement focus and harvest-now-decrypt-later motivation
- https://csrc.nist.gov/projects/post-quantum-cryptography
Supports
- Canonical NIST standards, selected algorithms, evaluation process, publications, and project status
- https://csrc.nist.gov/pubs/fips/203/final
Supports
- ML-KEM purpose, key generation, encapsulation, decapsulation, shared-secret use, and parameter sets
- Module Learning with Errors security foundation and 2024 publication milestone
- https://csrc.nist.gov/pubs/fips/204/final
Supports
- ML-DSA signature purpose, signing and verification roles, lattice foundation, and parameter sets
- 2024 publication milestone
- https://csrc.nist.gov/pubs/fips/205/final
Supports
- SLH-DSA stateless hash-based signature purpose, algorithm foundation, and parameter sets
- 2024 publication milestone
- https://csrc.nist.gov/pubs/ir/8105/final
Supports
- Quantum effects on public-key and symmetric cryptography
- April 2016 NIST migration framing, interoperability goal, and cryptographic-agility emphasis
- https://doi.org/10.1109/SFCS.1994.365700
Supports
- November 1994 publication of polynomial-time quantum algorithms for factoring and discrete logarithms
- https://doi.org/10.1145/237814.237866
Supports
- July 1996 publication of a quantum algorithm providing quadratic speedup for unstructured search
- https://www.rfc-editor.org/rfc/rfc9794.html
Supports
- Terminology and component distinctions for post-quantum traditional hybrid schemes
- Need for a specified combiner rather than an informal algorithm combination
- https://www.nccoe.nist.gov/applied-cryptography/migration-to-pqc
Supports
- Enterprise discovery, migration, interoperability, performance, and implementation project scope
- Migration ecosystem and technology-partner evidence for a real product market
- https://pages.nist.gov/ESCAPE-uPQC/
Supports
- Cryptographic discovery architecture, interoperability testing, and performance investigation
- Evidence-driven inventory and migration testing
- https://csrc.nist.gov/pubs/ir/8547/ipd
Supports
- Transition framing from quantum-vulnerable standards to PQC across products, services, and infrastructure
- https://www.nccoe.nist.gov/applied-cryptography/crypto-agility
Supports
- Controlled cryptographic replacement and agility as an enterprise capability
- https://www.ncsc.gov.uk/guidance/pqc-migration-timelines
Supports
- Staged discovery, planning, migration, and completion roadmap for PQC programs
- https://csrc.nist.gov/Projects/post-quantum-cryptography/post-quantum-cryptography-standardization/Call-for-Proposals
Supports
- December 2016 call for proposals and scope of public-key encryption, key establishment, and signatures
- https://www.nist.gov/publications/status-report-third-round-nist-post-quantum-cryptography-standardization-process
Supports
- December 2017 first-round start with 69 accepted candidates
- Round durations and narrowing through the third round
- https://www.nist.gov/news-events/news/2019/01/nist-reveals-26-algorithms-advancing-post-quantum-crypto-semifinals
Supports
- January 2019 selection of 26 second-round candidates
- Evaluation across servers, smartphones, smart cards, embedded devices, and chips
- https://www.nist.gov/news-events/news/2020/07/nists-post-quantum-cryptography-program-enters-selection-round
Supports
- July 2020 selection of seven finalists and eight alternates for round three
- https://www.nist.gov/news-events/news/2022/07/nist-announces-first-four-quantum-resistant-cryptographic-algorithms
Supports
- July 2022 selection of Kyber, Dilithium, FALCON, and SPHINCS+
- Distinct KEM and signature roles and need for mathematical diversity
- https://www.nist.gov/news-events/news/2023/08/nist-standardize-encryption-algorithms-can-resist-attack-quantum-computers
Supports
- August 2023 publication of draft FIPS 203, 204, and 205 for public comment
- https://www.nist.gov/news-events/news/2024/08/nist-releases-first-3-finalized-post-quantum-encryption-standards
Supports
- August 2024 final publication and intended use of FIPS 203, 204, and 205
- Eight-year NIST selection effort and immediate implementation guidance
- https://github.com/sindresorhus/awesome
Supports
- Required Awesome-list discovery starting point
- https://github.com/veorq/awesome-post-quantum
Supports
- Discovery of liboqs, PQClean, pqm4, CIRCL, Bouncy Castle, and the OpenSSL provider ecosystem
- https://openquantumsafe.org/liboqs/
Supports
- Common C API, test harness, benchmarks, algorithm implementations, wrappers, and integrations
- https://openquantumsafe.org/liboqs/security.html
Supports
- Research and prototyping scope, production limitations, security response, and audit information
- https://github.com/PQClean/PQClean
Supports
- Portable, tested implementations and NIST-compatible API organization
- https://github.com/mupq/pqm4
Supports
- Post-quantum implementation and benchmarking work for ARM Cortex-M4 targets
- https://github.com/cloudflare/circl
Supports
- Go implementations of ML-KEM, ML-DSA, SLH-DSA, hybrid-oriented primitives, and experimental-use warning
- https://www.bouncycastle.org/documentation/specification_interoperability/
Supports
- PQC standards mapping, algorithm identifiers, provider availability, and interoperability reference
- https://github.com/open-quantum-safe/oqs-provider
Supports
- OpenSSL 3 provider integration for post-quantum and hybrid experimentation
- https://aws.amazon.com/security/post-quantum-cryptography/
Supports
- AWS managed-service PQC placement, shared responsibility, migration workstreams, ML-KEM, and ML-DSA support
- https://docs.aws.amazon.com/kms/latest/developerguide/pqtls.html
Supports
- Hybrid post-quantum TLS behavior, client enablement, and performance considerations at AWS KMS endpoints
- https://aws.amazon.com/blogs/security/customer-compliance-and-security-during-the-post-quantum-cryptographic-migration/
Supports
- Hybrid key-establishment composition, added handshake data, interoperability, and negotiation verification
- https://www.cloudflare.com/pqc/
Supports
- Cloudflare network-path placement for hybrid ML-KEM across websites, applications, Zero Trust, and gateways
- https://developers.cloudflare.com/ssl/post-quantum-cryptography/pqc-cloudflare-products/
Supports
- Per-connection PQC status and requirement that both ends support compatible algorithms
- https://cloud.google.com/blog/products/identity-security/announcing-quantum-safe-digital-signatures-in-cloud-kms
Supports
- Managed Cloud KMS support for ML-DSA and SLH-DSA signing and verification
- https://cloud.google.com/blog/products/identity-security/announcing-quantum-safe-key-encapsulation-mechanisms-in-cloud-kms/
Supports
- Managed Cloud KMS support and code-sample path for post-quantum key encapsulation
- https://www.ibm.com/quantum-safe
Supports
- IBM Quantum Safe discovery, assessment, and remediation product placement
- https://www.qusecure.com/quprotect/
Supports
- QuProtect discovery, remediation orchestration, CBOM, and reporting roles
- https://www.sandboxaq.com/solutions/aqtive-guard
Supports
- AQtive Guard cryptographic inventory, posture management, and PQC migration placement
- https://www.digicert.com/solutions/post-quantum-computing
Supports
- DigiCert ONE certificate discovery, lifecycle automation, device identity, and PQC readiness placement
- https://www.keyfactor.com/products/cryptographic-discovery-inventory/
Supports
- AgileSec discovery, cryptographic context, vulnerability analysis, and PQC prioritization placement
- https://pqshield.com/products/
Supports
- PQShield software and hardware implementations, standardized algorithms, target profiles, and side-channel controls