Algorithmic Agility in MCP Server-Client Cryptographic Negotiation

Executive summary: This blog post advocates building cryptographic agility into MCP client-server handshakes to defend AI-backed systems against 'harvest now, decrypt later' quantum threats. It outlines negotiation mechanics (client algorithm advertisement, server MTI policies, suite identifiers), post-quantum and hybrid signature/key-exchange approaches, anti-downgrade protections, session re-keying and resumption using PQC, and practical deployment concerns—performance, key sizes, legacy-client isolation, and phased migration (SHOULD+/MUST-). The piece emphasizes modular designs that let operators swap algorithms quickly to balance long-term secrecy with real-world latency and interoperability constraints.