DACP v0.1.1 Specification: Delegation Credential Protocol for Autonomous Agent Commerce

This specification defines the Delegation Credential Protocol (DACP) version 0.1.1, a JSON-LD, Ed25519-signed, version-locked, revocable credential format for autonomous agent spend delegation. DACP provides a complete credential lifecycle from issuance through revocation, with explicit support for audience scoping, replay-attack protection via UUIDv4 nonces, and Merkle-tree-based batch revocation. The protocol introduces formal signature envelope structures with algorithm identification and key reference, canonical signing using URDNA2015 normalization with SHA-256 (standard) or SHA-512 (high-value credentials), constraint-narrowing inheritance for sub-delegation chains, and extension namespaces for application-specific metadata. This specification provides field-by-field schema definitions, cryptographic procedures, security properties, revocation models, version negotiation mechanisms, and complete conformance test vectors. DACP forms the foundational delegation layer of the Agent Delegated Purchasing Protocol (ADPP), enabling cryptographically verifiable authority transfer from human principals to autonomous agents with constraint-bounded purchasing authority.