Elpis Protocol: Infrastructure-Level Cryptographic Identity for Autonomous AI Agents

As AI agents become autonomous network participants, the absence of standardized, verifiable identity creates systemic vulnerabilities including impersonation, unauthorized resource access, and regulatory non-compliance. This paper presents the Elpis Protocol, an infrastructure-level cryptographic identity framework anchored on the XRP Ledger (XRPL). Elpis operates transparently within the agent's execution environment, requiring zero application-level changes. The protocol introduces a Three-Tier Identity model (Root CA, Provider CA, Agent Certificate), a Four-Level Escalation mechanism for graduated incident response, and a Two-Tier Reputation system combining on-chain attestations with off-chain behavioral scoring. A reference implementation demonstrates sub-5ms validation overhead via a transparent signing proxy that attaches cryptographic identity headers to all outbound requests. Elpis is fully compatible with existing OAuth 2.0, mTLS, and OpenID Connect infrastructure.