Public API endpoints
Harvest-now-decrypt-later exposure for sensitive traffic crossing the internet.
Confirm TLS 1.3 support and provider support for hybrid ML-KEM key exchange.
Partner APIs and webhooks
Third-party clients, callback URLs and signing schemes can block migration.
Inventory clients, certificates, webhook signatures and token validation rules.
Internal service APIs
Service meshes, mTLS, sidecars and platform certificates can hide cryptographic dependencies.
Map mTLS, certificate authorities, service identity and key rotation workflows.
Why APIs Need Their Own PQC Plan
Website guidance usually focuses on browser traffic. APIs are different because they serve mobile apps, business partners, internal services, automation, payment flows and webhook callbacks. Each client type can have a different TLS stack, certificate policy and signing requirement.
For post-quantum cryptography, the first question is not only whether the public host supports modern TLS. It is whether the whole API path can move without breaking client compatibility, monitoring, gateways, service identity or audit controls.
What an External API Scan Can See
TLS version support
Whether the API host negotiates TLS 1.3 and avoids legacy protocol exposure.
Hybrid key exchange signals
Whether post-quantum hybrid key exchange is observed at the edge.
Certificate and hostname posture
Whether the public endpoint has basic certificate hygiene and a clear canonical host.
Header posture
Whether browser-facing API hosts expose avoidable transport and content security gaps.
External scans are a starting point. They cannot prove that every internal service, private endpoint, JWT issuer, webhook signer or data store is quantum-safe.
API PQC Migration Checklist
- 1. Inventory every API host. Include public APIs, admin APIs, mobile backends, webhook receivers, partner callbacks and private service endpoints.
- 2. Rank data by lifetime. Prioritise APIs that carry regulated, financial, health, identity, government or commercially sensitive data.
- 3. Check transport readiness. Move eligible endpoints to TLS 1.3 and test hybrid ML-KEM support with the edge provider, gateway or CDN.
- 4. Separate transport from signatures. TLS key exchange does not replace JWT, webhook, document, code-signing or certificate signature migration.
- 5. Test client compatibility. Mobile SDKs, embedded clients and partner integrations may lag behind browser and CDN support.
- 6. Document crypto-agility. Make algorithms, key sizes, certificate chains and library versions visible in architecture and runbooks.
Common API Dependencies to Review
| Dependency | Quantum migration question |
|---|---|
| API gateway or CDN | Can it negotiate TLS 1.3 and hybrid ML-KEM at the edge? |
| mTLS certificates | Which certificate authorities, algorithms and client stores are involved? |
| JWT and token signing | Where are RSA or ECDSA signatures used, and how long must tokens or audit records remain trustworthy? |
| Webhook signatures | Which partners verify signatures, and how will algorithm changes be rolled out? |
| Secrets and stored payloads | Does API traffic get logged, queued, mirrored or stored under classical encryption? |
Primary References
Check an API Host Before the Full Audit
Start with an external scan of the API hostname, then use the results to prioritise deeper inventory work across gateways, mTLS, tokens and partner clients.
Free readiness account
Keep This Guide Connected to a Real Website Scan
A PQC guide is more useful when it is attached to current evidence. Create a free account, add a public domain now or later, and keep a repeatable baseline for TLS, security headers and visible post-quantum readiness.
No cardStart the free evidence path without a paid plan.
Saved scanKeep the public endpoint result after the browser session.
Rescan laterRerun after TLS, header or provider changes.
Prefer to scan first? Open the free quantum security scanner.