x402 payment protocol: handshake is standardized but adversarial security suite is missing

Short summary

The x402 payment protocol moved from Coinbase to the Linux Foundation with backing from Stripe, Cloudflare, Visa, and others, aiming to be 'SSL for AI commerce.' While the specification and functional conformance tests exist, the author argues it lacks a normative adversarial security suite defining hostile conditions every implementation must survive. Key concerns include cross-verifier consistency, replay attacks, and facilitator requirement substitution.

• •x402 protocol moved to Linux Foundation with major industry backing for AI commerce payments
• •Specification covers functional conformance but lacks adversarial security test suites
• •Critical gap: cross-verifier consistency — independent verifiers may reach different security conclusions on the same payment payload

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