MPP machine payment security and delegated authorization

What the protocol establishes

MPP is a payment-method-agnostic HTTP 402 authorization framework. MandateShield maps a canonical Payment charge challenge only under the explicit MANDATESHIELD_PORTABLE_CHARGE_V1 integrator profile; it does not verify the method credential, select a method or execute settlement. Strict authority uses a separate account-pinned MandateShield JWS.

Five checks before execution

1. Resolve the final MPP provider, resource, amount and currency before authorization.
2. Confirm the method-specific request maps to MANDATESHIELD_PORTABLE_CHARGE_V1, then normalize those exact terms.
3. Bind the envelope to fresh authority signed by the account-pinned issuer.
4. Enforce per-attempt and cumulative budgets atomically across concurrent agents.
5. Require the trusted gateway to consume the reservation once before constructing or submitting the MPP credential.

The gap MandateShield closes

A valid MPP challenge and credential establish payment-protocol semantics, not that a person or enterprise approved the exact provider, resource and price selected by the agent.

MandateShield normalizes execution facts and returns a deterministic decision with exact findings. Strict v2 verifies supported evidence and returns an ES256-signed receipt with public transparency; it complements the protocol's wider trust and settlement chain.