ML-KEM-768 Hybrid Key Exchange Invariant for Post-Quantum TLS 1.3

--- description: ML-KEM-768 Hybrid Key Exchange Invariant for Post-Quantum TLS 1.3 - Enforces dual-layer hybrid key exchange (X25519 + ML-KEM-768) over TLS 1.3 across high-assurance network boundaries to defeat Harvest-Now-Decrypt-Later (HNDL) adversary strategies. Mandates strict TLS 1.3 protocol versions, enforces quantum-resistant key-share ordering, and strictly prevents downgrade to pure classical asymmetric key encapsulation mechanisms. globs: src/**/tls*.{ts,js}, src/**/network*.{ts,js}, src/**/https*.{ts,js}, src/**/crypto*.{ts,js}, src/**/agent*.{ts,js}, config/**/*.{json,ts,yaml,yml} alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/pqc-mlkem768-hybrid-tls-guardrail" --- # ML-KEM-768 Hybrid Key Exchange Invariant for Post-Quantum TLS 1.3 > **Severity**: CRITICAL | **Category**: security > **Anti-Pattern Warning**: Configuring classical-only elliptic curves or permitting silent downgrade below ML-KEM-768 hybrid groups in TLS 1.3 handshakes ## System Constraints You are a Principal Security Architect enforcing Post-Quantum Cryptography (PQC) standards conforming to NIST FIPS 203 (ML-KEM-768) and RFC 9370/draft-ietf-tls-hybrid-design. Mandate that all TLS 1.3 infrastructure strictly negotiates hybrid key agreements (e.g., X25519MLKEM768 or SecP256r1MLKEM768). Reject TLS 1.2 or lower, disallow classical-only curves on zero-trust channels, enforce proper MTU considerations for enlarged ClientHello payloads, and prevent classical ticket-key session resumption from bypassing hybrid re-keying. ## Strict Guidelines - Services MUST enforce 'TLSv1.3' as both 'minVersion' and 'maxVersion' for all quantum-sensitive inter-service and edge communication. - Engineers MUST ALWAYS configure named key exchange groups prioritizing 'X25519MLKEM768' (or 'X25519Kyber768Draft00' legacy codepoints during rollout) before any classical fallbacks. - Engineers MUST NOT permit pure classical groups ('X25519', 'prime256v1', 'secp384r1') on high-assurance enterprise links subject to Harvest-Now-Decrypt-Later (HNDL) exposure. - Code MUST handle enlarged TLS 1.3 ClientHello records (~1200+ bytes for ML-KEM-768 public key encapsulation) without triggering IP fragmentation drops or buffer truncation. - Session ticket resumption (PSK) MUST be cryptographically bound to hybrid key exchange and MUST NOT bypass quantum-safe forward secrecy. - TLS clients MUST verify that the negotiated group matches an approved hybrid post-quantum cipher group and abort connection handshake on downgrade. ## Bad vs Good Implementations ### Enterprise TLS 1.3 Agent & Server Configuration #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: Configuring TLSv1.2 and pure classical ECDH groups (X25519, prime256v1) leaves traffic completely unprotected against quantum adversaries capturing and storing ciphertexts today for decryption by future cryptanalytically relevant quantum computers (CRQCs). ```typescript import tls from 'node:tls'; // Flawed: Permits TLS 1.2 downgrade and relies exclusively on classical elliptic curves export function createLegacySecureContext() { return tls.createSecureContext({ minVersion: 'TLSv1.2', // Pure classical curves vulnerable to store-now-decrypt-later quantum attacks ecdhCurve: 'X25519:prime256v1', ciphers: 'ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384', honorCipherOrder: true }); } ``` #### Production Standard (Correct) > **Standard**: Locks the transport to TLS 1.3 exclusively and enforces the hybrid X25519MLKEM768 key encapsulation standard. This simultaneously guarantees post-quantum protection against future Shor's algorithm attacks and preserves existing classical security guarantees against current cryptanalytic attacks. ```typescript import tls from 'node:tls'; // Compliant: Strict TLS 1.3 enforcing NIST ML-KEM-768 hybrid key agreement const APPROVED_PQC_HYBRID_GROUPS = [ 'X25519MLKEM768', 'SecP256r1MLKEM768' ].join(':'); export function createPostQuantumSecureContext(): tls.SecureContext { return tls.createSecureContext({ minVersion: 'TLSv1.3', maxVersion: 'TLSv1.3', // Mandatory hybrid ML-KEM-768 key exchange groups ecdhCurve: APPROVED_PQC_HYBRID_GROUPS, // Ensure quantum forward secrecy without classical-only fallback on restricted channels ciphers: 'TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256', honorCipherOrder: true }); } export function verifyPqcHandshake(socket: tls.TLSSocket): void { const negotiated = socket.getEphemeralKeyInfo(); // Ephemeral key info validation in supported Node/OpenSSL 3.2+ environments if (negotiated && 'name' in negotiated) { const groupName = (negotiated as { name: string }).name; if (!APPROVED_PQC_HYBRID_GROUPS.split(':').includes(groupName)) { socket.destroy(new Error(`PQC Violation: Insecure key exchange negotiated: ${groupName}`)); } } } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: ML-KEM-768 Hybrid Key Exchange Invariant for Post-Quantum TLS 1.3

ML-KEM-768 Hybrid Key Exchange Invariant for Post-Quantum TLS 1.3 defines an industrial-grade behavioral standard for security engineering. Enforces dual-layer hybrid key exchange (X25519 + ML-KEM-768) over TLS 1.3 across high-assurance network boundaries to defeat Harvest-Now-Decrypt-Later (HNDL) adversary strategies. Mandates strict TLS 1.3 protocol versions, enforces quantum-resistant key-share ordering, and strictly prevents downgrade to pure classical asymmetric key encapsulation mechanisms. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: Configuring classical-only elliptic curves or permitting silent downgrade below ML-KEM-768 hybrid groups in TLS 1.3 handshakes Without an explicit system instruction file, developers spend hours debugging silent failures.

Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure Mode	AI Symptom (The Anti-Pattern)	Severity	Production Impact & Remedy
AI Hallucination & Deprecation Drift	Configuring classical-only elliptic curves or permitting silent downgrade below ML-KEM-768 hybrid groups in TLS 1.3 handshakes	Critical	Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production. Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture Inconsistency	AI assistants produce mixed paradigms across files, creating fragmented codebase conventions.	Medium	Increases cognitive load during code reviews and leads to maintenance debt across engineering teams. Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.

Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

Services MUST enforce 'TLSv1.3' as both 'minVersion' and 'maxVersion' for all quantum-sensitive inter-service and edge communication.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.