Agent Integrity & Response Seals

Response seals provide cryptographic tamper-evidence for every LLM response in the Veridex agent runtime. They ensure that model outputs haven't been modified between the provider and your application.

How It Works

Verifying Response Seals

import { verifyResponseSeal } from '@veridex/agents';
 
// From a ResponseEnvelope
const envelope = result.envelope;
 
if (envelope.chainOfCustodySeal) {
  const isValid = verifyResponseSeal(
    envelope.chainOfCustodySeal,
    rawResponseBytes,
    apiKeyBytes,
  );
 
  if (!isValid) {
    console.error('Response may have been tampered with!');
  }
}

ResponseEnvelope Structure

Every agent run turn produces a ResponseEnvelope:

interface ResponseEnvelope {
  runId: string;
  turnIndex: number;
  model: string;
  provider: string;
  output: string;
  tokensUsed: {
    prompt: number;
    completion: number;
  };
  chainOfCustodySeal?: {
    algorithm: 'HMAC-SHA256';
    seal: string;      // hex-encoded HMAC
    rawHash: string;   // SHA-256 of raw response bytes
    timestamp: number; // Unix ms when seal was created
  };
}

Seal Cryptography

The signing key is derived using:

• IKM: API key bytes
• Salt: "veridex-response-seal-v1"
• Info: "hmac-signing-key"

Supported Providers

All built-in model providers automatically create seals:

Agent Integrity Bindings

Beyond response seals, agents can bind their identity to a specific code + config snapshot:

interface AgentIntegrityBinding {
  agentId: string;
  identityClaims: AgentIdentityClaims;
  codeHash: string;           // SHA-256 of agent code
  configHash: string;         // SHA-256 of agent configuration
  toolManifestHash: string;   // SHA-256 of registered tools
  timestamp: number;
}

This allows auditors to verify that an agent's behavior matches its declared capabilities at the time of execution.

Integration with Audit Trail

Response seals are automatically:

• Logged by RawResponseHashLogger for offline verification
• Included in trace records via the control plane
• Available in evidence bundles via generateEvidenceBundle()

Related

• Agents Framework — ResponseSeal API
• API Reference — Full type signatures
• Governance: Traces — Audit trail
• Security: Response Integrity — Security implications