MPCP Authorization Chain
The authorization chain is the core visual model for MPCP. Each step produces a verifiable artifact that constrains the next. PolicyGrant and SignedBudgetAuthorization are cryptographically signed; the Trust Gateway verifies both signatures before submitting settlement. Machines spend within bounds established upstream—no per-transaction approval required.
PolicyGrant → SBA → Trust Gateway → XRPL Settlement → Receipt
In fleet deployments, an optional FleetPolicyAuthorization (FPA) layer may sit above PolicyGrant.
Fleet Policy
↓
PolicyGrant
↓
SignedBudgetAuthorization (SBA)
↓
Trust Gateway
↓
XRPL Settlement → Receipt
What Each Step Does
| Step | Artifact | Purpose |
|---|---|---|
| Fleet Policy | Policy definition | Rules: rails, assets, vendors, caps |
| PolicyGrant | Session entry | "This machine may initiate payment under these constraints" |
| SignedBudgetAuthorization | Spending envelope | "Up to X, on these rails, to these destinations" |
| Trust Gateway | Settlement executor | Verifies the authorization chain and submits the XRPL transaction |
| Receipt | txHash | Confirmed on-chain settlement result |
Key Idea
Approval moves upstream. The human or policy administrator grants a session and budget. The machine spends within that budget. The Trust Gateway verifies the chain and executes settlement — no separate per-payment authorization artifact is required.
See Also
- System Model — How the chain fits in the overall architecture
- Artifact Lifecycle — When each artifact is created
- Reference Flow — Full EV charging walkthrough
- Protocol: Artifacts — Detailed artifact specs