Cryptographic signing, replay protection, and E2E encryption for AI agent messages. One envelope. Every transport. Quantum-ready.

The Problem
What 7h3 Protocol Does
How It Works
Security Guarantees
Installation
Quick Start
Core API
Transports
Gateway
Cloudflare Workers
AI Coding Agents
MCP (Claude Tool Calls)
End-to-End Encryption
Capability Tokens and Delegation
Streaming Message Signing
Distributed Replay Cache (Redis)
Binary Wire Format (CBOR)
Observability (Prometheus + OpenTelemetry)
Post-Quantum Signatures (ML-DSA)
Threshold Signatures (M-of-N BLS)
Audit Log
Rate Limiting
Route Policies
Key Infrastructure
Cross-SDK Conformance
CLI Reference
Docker
Uninstall
Changelog
License

The Problem

AI agent systems are moving fast, and the protocols underpinning them were not built with message-level security in mind.

MCP (Model Context Protocol) is plain JSON-RPC 2.0. A message in flight has no signature. Any intermediary — a rogue proxy, a compromised queue consumer, a misconfigured load balancer — can alter tool call parameters or replay a previously captured request. The MCP handler has no way to know.

A2A (Agent-to-Agent) signs Agent Cards — static configuration — not per-message traffic. Once an agent is "trusted," every message it sends is implicitly trusted regardless of whether that specific message was tampered with in transit or is a replay from ten minutes ago.

HTTP APIs default to IP-based rate limiting. IP addresses are trivially spoofed or shared. The same valid signed request can often be submitted multiple times, triggering duplicate writes, payments, or tool executions.

The gap these protocols share is identical: they authenticate agents at the connection or identity level, but they do not authenticate individual messages at the content level. 7h3 Protocol fills that gap without replacing anything.

What 7h3 Protocol Does

7h3 Protocol wraps every message — regardless of transport — in a signed envelope. The envelope is compact, deterministic, and verifiable by any peer that holds the sender's public key.

Feature set:

Feature	Mechanism
Message authentication	Ed25519 asymmetric signing or HMAC-SHA256
Replay prevention	TTL + nonce deduplication (in-memory or Redis)
E2E encryption	X25519 key exchange + ChaCha20-Poly1305 AEAD
Capability delegation	Scoped, time-bounded, cryptographic credential chains
Streaming signing	Per-chunk HMAC + final Ed25519 over the full stream
Observability	Zero-dep Prometheus exposition + optional OpenTelemetry
Post-quantum	ML-DSA-65 / ML-DSA-87 (NIST FIPS 204) — `@7h3/protocol-pq`
Binary encoding	Deterministic CBOR (RFC 8949) — ~40% smaller than JSON
Threshold signing	M-of-N BLS12-381 aggregation — `@7h3/protocol-threshold`
Transport coverage	HTTP, WebSocket, gRPC, Queues, Webhooks
SDK coverage	TypeScript, Python, Rust, Go, Browser

How It Works

Canonical Serialization

Signatures only mean something if everyone signs the same bytes. JSON object key order is unspecified by the spec, so 7h3 Protocol uses deterministic JSON canonicalization: keys are sorted alphabetically at every nesting level, optional absent fields are omitted entirely, and the result is UTF-8 encoded.

The canonical form is byte-identical across TypeScript, Python, Rust, and Go, proven by the shared conformance test vectors in conformance/7h3_v0_1.json.

Envelope Structure

{
  "body": {
    "capability":   "task.plan",
    "content":      "do something",
    "correlationId": "req-123",
    "intent":       "TASK"
  },
  "header": {
    "messageId":   "uuid-here",
    "nonce":       "random-bytes",
    "recipient":   "agent.beta",
    "sender":      "agent.alpha",
    "timestampMs": 1712500000000,
    "ttlMs":       60000,
    "version":     "7h3/0.1"
  },
  "signature": {
    "alg":   "ED25519",
    "keyId": "k1",
    "value": "base64url-sig-here"
  }
}

Optional fields (capability, correlationId, recipient) are omitted when absent — not null, not "". This is load-bearing for the canonical form.

End-to-End Flow

sequenceDiagram
    autonumber

    participant Sender as Sender Agent
    participant SDK as 7h3 SDK
    participant Transport
    participant Gateway as Gateway / Receiver
    participant Upstream

    Sender->>SDK: Create envelope with sender, body, and TTL
    SDK->>SDK: Canonicalize JSON deterministically
    SDK->>SDK: Sign payload using Ed25519
    SDK-->>Sender: Return signed envelope

    Sender->>Transport: Send via HTTP, WebSocket, gRPC, queue, or webhook
    Transport->>Gateway: Deliver signed envelope

    Gateway->>Gateway: Validate TTL
    Gateway->>Gateway: Reject replayed nonce
    Gateway->>Gateway: Verify Ed25519 signature
    Gateway->>Gateway: Apply route policy and rate limit

    Gateway->>Upstream: Forward request with x-7h3-sender header
    Upstream-->>Gateway: Return response
    Gateway-->>Sender: Return response, optionally signed

TTL and Nonce

Every envelope carries timestampMs, ttlMs, and a random nonce. A receiver rejects the envelope if now > timestampMs + ttlMs, then checks the nonce against a deduplication store. A replayed envelope fails even if the signature is valid.

Security Guarantees

Attack	Defense
Impersonation	Ed25519 — only the private key holder can produce a valid signature
Replay	Nonce deduplication + TTL expiry (in-memory or Redis)
Tampering	Signature covers the full canonical envelope; any modification breaks verification
Unauthorized access	Per-route `allowedSenders` policy — unlisted senders rejected before upstream
Response spoofing	Signed `x-7h3-response` header; `correlationId` binding
Rate abuse	`SlidingWindowRateLimiter` keyed by verified sender identity, not IP
Audit tampering	`InMemoryAuditLog` entries are Ed25519-signed and chained
Quantum computers	ML-DSA-65/87 via `@7h3/protocol-pq` (NIST FIPS 204)
Cross-instance replay	`RedisReplayStore` — atomic SET NX PX across all instances
Eavesdropping	X25519 + ChaCha20-Poly1305 E2E encryption

Installation

TypeScript / Node.js

npm install @7h3/protocol
# or
pnpm add @7h3/protocol
# or
yarn add @7h3/protocol

Requires Node.js ≥ 20 (CI tests on Node 22). Zero runtime dependencies — uses Node.js built-in crypto throughout.

Python

pip install 7h3-protocol

Requires Python ≥ 3.9. Optional extras for advanced features:

pip install 7h3-protocol[crypto]   # X25519 + ChaCha20 encryption (cryptography)
pip install 7h3-protocol[nacl]     # Alternative crypto backend (PyNaCl)

RedisReplayStore and ML-DSA post-quantum support have no dedicated extra — install their backends directly (pip install redis, pip install dilithium-py); each module raises a clear ImportError telling you which package it needs if it's missing.

Rust

# Cargo.toml
[dependencies]
protocol-7h3 = "0.5"

Go

go get github.com/IceMasterT/7h3-protocol/sdk/go

Browser

npm install @7h3/protocol-browser

Pure Web Crypto API — no Node.js dependency. Works in Chrome 100+, Firefox 100+, Safari 16+, Edge 100+.

Post-Quantum Extension

npm install @7h3/protocol-pq

Adds ML-DSA-65 and ML-DSA-87 (NIST FIPS 204 / Dilithium). Separate package to keep @7h3/protocol at zero runtime dependencies.

Threshold Signatures Extension

npm install @7h3/protocol-threshold

Adds M-of-N BLS12-381 threshold signatures and Shamir Secret Sharing.

Quick Start

import {
  generateEd25519KeypairBase64Url,
  createEnvelope,
  signEnvelopeEd25519,
  verifyEnvelopeEd25519,
} from '@7h3/protocol'

// 1. Generate keypairs
const sender   = await generateEd25519KeypairBase64Url()
const receiver = await generateEd25519KeypairBase64Url()

// 2. Create and sign a message
const envelope = createEnvelope({
  sender:  'agent.alpha',
  intent:  'TASK',
  content: 'summarize https://example.com',
  ttlMs:   60_000,
})

const signed = await signEnvelopeEd25519(envelope, sender.privateKey, 'key-1')

// 3. Transmit `signed` via any transport (HTTP header, WS frame, queue, etc.)

// 4. Verify on the receiving end
const ok = await verifyEnvelopeEd25519(signed, sender.publicKey)
if (!ok) throw new Error('signature verification failed')

console.log('Verified sender:', signed.header.sender)  // 'agent.alpha'

Core API

Key Generation

TypeScript:

import { generateEd25519KeypairBase64Url } from '@7h3/protocol'

const { publicKey, privateKey } = await generateEd25519KeypairBase64Url()
// publicKey:  SPKI format, base64url, ~44 chars
// privateKey: PKCS8 format, base64url, ~88 chars

Python:

The Python SDK has no built-in keygen helper — generate directly with cryptography (PKCS8 private / SPKI public, base64url-encoded, matching every other SDK's key format):

import base64
from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
from cryptography.hazmat.primitives import serialization

b64 = lambda b: base64.urlsafe_b64encode(b).decode('ascii').rstrip('=')

priv = Ed25519PrivateKey.generate()
private_key = b64(priv.private_bytes(
    encoding=serialization.Encoding.DER,
    format=serialization.PrivateFormat.PKCS8,
    encryption_algorithm=serialization.NoEncryption(),
))
public_key = b64(priv.public_key().public_bytes(
    encoding=serialization.Encoding.DER,
    format=serialization.PublicFormat.SubjectPublicKeyInfo,
))

Rust:

The Rust SDK only parses PKCS8/SPKI keys — it has no keygen helper either. Generate a keypair with the CLI (npx 7h3 keygen) or another SDK, then pass the resulting base64url strings into sign_envelope_ed25519 / verify_envelope_ed25519 (see below).

Go:

import go7h3 "github.com/IceMasterT/7h3-protocol/sdk/go"

publicKey, privateKey, err := go7h3.GenerateKeypair()

Browser:

import { generateKeypair } from '@7h3/protocol-browser'

const { publicKey, privateKey } = await generateKeypair()

Creating Envelopes

import { createEnvelope } from '@7h3/protocol'

const envelope = createEnvelope({
  sender:        'agent.alpha',
  intent:        'TASK',
  content:       'do something',
  capability:    'task.plan',     // optional
  correlationId: 'req-123',       // optional
  ttlMs:         60_000,          // default: 60000 (1 minute)
  recipient:     'agent.beta',    // optional
  messageId:     'custom-uuid',   // optional — auto-generated if omitted
})

Signing

Ed25519 (asymmetric — recommended):

import { signEnvelopeEd25519 } from '@7h3/protocol'

const signed = await signEnvelopeEd25519(envelope, privateKey, 'key-id')
// signed.signature.alg === 'ED25519'

HMAC-SHA256 (shared secret):

import { signEnvelopeHmac } from '@7h3/protocol'

const signed = await signEnvelopeHmac(envelope, sharedSecret, 'key-id')
// signed.signature.alg === 'HS256'

Python:

from protocol_7h3 import sign_envelope_ed25519, sign_envelope_hmac

signed = sign_envelope_ed25519(envelope, private_key, 'k1')
signed = sign_envelope_hmac(envelope, shared_secret, 'k1')

Rust:

use protocol_7h3::{sign_envelope_ed25519, sign_envelope_hmac};

let signed = sign_envelope_ed25519(&envelope, &private_key, "k1")?;   // Result<_, String>
let signed = sign_envelope_hmac(&envelope, &shared_secret, "k1");     // infallible, no `?`

Go:

// Ed25519: keyId is derived internally from the public key, not passed in
signed, err := go7h3.SignEnvelopeEd25519(env, privateKey)
signed, err := go7h3.SignEnvelopeHmac(env, sharedSecret, "k1")

Verifying

TypeScript:

import { verifyEnvelopeEd25519, verifyEnvelopeHmac } from '@7h3/protocol'

const ok = await verifyEnvelopeEd25519(signed, publicKey)  // Promise<boolean>
if (!ok) throw new Error('signature verification failed')

const ok2 = await verifyEnvelopeHmac(signed, sharedSecret)

Signature validity alone doesn't check TTL expiry or required fields — call validateEnvelope(signed) (returns ProtocolDiagnostic[]) alongside verification for full checks.

Python:

from protocol_7h3 import verify_envelope_ed25519

if not verify_envelope_ed25519(signed, public_key):  # returns bool
    raise ValueError('signature verification failed')

Rust:

use protocol_7h3::verify_envelope_ed25519;

let result = verify_envelope_ed25519(&signed, &public_key)?;

Go:

ok, err := go7h3.VerifyEnvelopeEd25519(signed, publicKey)

Transports

The same signed envelope is carried differently per transport. Verification logic is identical.

HTTP / REST

The signed envelope travels as a JSON value in the x-7h3-envelope header.

Signing outbound requests:

import { createEnvelope, signHttpRequest } from '@7h3/protocol'

const envelope = createEnvelope({
  sender:  'agent.alpha',
  intent:  'TASK',
  content: JSON.stringify(payload),
})

const { headers } = await signHttpRequest(envelope, myPrivateKey)

await fetch('https://api.example.com/action', {
  method:  'POST',
  headers: { ...headers, 'Content-Type': 'application/json' },
  body:    JSON.stringify(payload),
})

Verifying inbound requests (Express middleware):

import { verifyHttpEnvelope, createStaticKeyRegistry } from '@7h3/protocol'

const keyRegistry = createStaticKeyRegistry(keyStore)   // { [senderId]: publicKey }

app.use(async (req, res, next) => {
  const result = await verifyHttpEnvelope(req.headers, { keyRegistry })
  if (!result.ok) return res.status(401).json({ error: result.reason })
  req.sender = result.envelope.header.sender
  next()
})

Python:

from protocol_7h3 import build_signed_request_headers, verify_http_envelope, StaticKeyRegistry

# Signing — convenience wrapper builds the envelope and signs it in one call
headers = build_signed_request_headers(
    sender='agent.alpha', private_key=my_private_key,
    content=json.dumps(payload),
)

# Verifying (FastAPI/Flask middleware)
registry = StaticKeyRegistry(key_store)   # { sender_id: public_key }
ok, envelope, reason = verify_http_envelope(request.headers, registry)
if not ok:
    raise ValueError(reason)

Go:

// go7h3.Middleware wraps an http.Handler directly — it verifies each
// request's envelope before calling next.
handler := go7h3.Middleware(keyRegistry, myHandler)
http.ListenAndServe(":8080", handler)

CBOR encoding (smaller payloads):

const { headers, body } = await signHttpRequest(envelope, myPrivateKey, { format: 'cbor' })
// headers['content-type'] === 'application/7h3-cbor'
// body: Uint8Array — send this as the request body instead of JSON

WebSocket

Every frame is individually signed. Sequence numbers prevent reordering attacks.

import { wrapWebSocket, createStaticKeyRegistry } from '@7h3/protocol'

const ws = new WebSocket('wss://api.example.com')

// Sender
const binding = wrapWebSocket(ws, {
  sender:      'agent.alpha',
  privateKey:  myPrivateKey,
  keyRegistry: createStaticKeyRegistry(keyStore),   // to verify incoming frames too
})
await binding.send({ do: 'something' })   // payload is wrapped in a TASK envelope automatically

// Receiver
binding.onMessage((payload, envelope) => {
  console.log('Verified from:', envelope.header.sender)
})
binding.onVerifyFail((err, rawData) => {
  console.warn('Rejected frame:', err.message)
})

gRPC

Envelope in 7h3-envelope-bin gRPC metadata (JSON, -bin suffix per gRPC convention).

import { signGrpcCall, withGrpcVerification, createStaticKeyRegistry } from '@7h3/protocol'

// Client — build metadata to attach to the outbound call
const metadata = await signGrpcCall({ sender: 'agent.alpha', privateKey, ttlMs: 60_000 })
const call = client.myMethod(request, metadata)

// Server — wrap any async handler with verify logic
const verifiedHandler = withGrpcVerification(myHandler, {
  keyRegistry: createStaticKeyRegistry(keyStore),
})
// call.7h3Envelope holds the verified envelope inside myHandler; throws (with a gRPC
// status `code`) on missing/invalid/expired envelopes

Message Queues

Envelope wraps payload as { envelope, payload }. Works with SQS, RabbitMQ, Kafka, Pub/Sub.

import { signQueueMessage, verifyQueueMessage } from '@7h3/protocol'

// Producer — returns a ready-to-send JSON string: {"envelope": ..., "payload": ...}
const message = await signQueueMessage(
  { taskId: '123', action: 'process' },
  { sender: 'agent.alpha', privateKey, keyId: 'k1' }
)
await queue.send(message)

// Consumer — takes the raw JSON string directly; throws on invalid/expired/tampered
try {
  const { payload, envelope } = await verifyQueueMessage(rawMessage, { publicKey })
  processTask(payload)
} catch (err) {
  console.warn('Rejected queue message:', err)
}

Pass the same replayCache instance (e.g. new InMemoryReplayCache()) to every verifyQueueMessage/verifyQueueBatch call in a consumer process to dedupe replayed messages.

Webhooks

Compact x-7h3-sig header (HMAC or Ed25519) plus x-7h3-ts timestamp.

import { signWebhookHmac, verifyWebhookHmac, InMemoryWebhookReplayCache } from '@7h3/protocol'

// Sender (HMAC shared-secret — use signWebhook/verifyWebhook for Ed25519 instead)
const headers = await signWebhookHmac(body, { secret: sharedSecret, ttlMs: 300_000 })
// Sets: x-7h3-sig, x-7h3-ts

// Receiver — returns a plain boolean; pass a replayCache to reject re-delivery
const replayCache = new InMemoryWebhookReplayCache()
const ok = await verifyWebhookHmac(body, req.headers, {
  secret:    sharedSecret,
  maxAgeMs:  300_000,
  replayCache,
})
if (!ok) return res.status(401).end()

Gateway

The Protocol7h3Gateway is a reverse proxy that verifies envelopes before forwarding to upstream. Drop it in front of any existing service.

createGateway() returns a verify()/handle() object — it doesn't bind a port itself, so pair it with any HTTP server (Node's http, Express, a Workers fetch handler, etc.):

import { createServer } from 'node:http'
import { createGateway } from '@7h3/protocol/gateway'
import { createStaticKeyRegistry } from '@7h3/protocol/key-registry'

const gateway = createGateway({
  upstream:    'http://localhost:3001',
  keyRegistry: createStaticKeyRegistry({
    'agent.alpha': alphaPublicKey,
    'agent.beta':  betaPublicKey,
    'agent.admin': adminPublicKey,
  }),
  policies: [
    {
      path:           '/api/admin/**',
      require:        'ed25519',
      allowedSenders: ['agent.admin'],
      rateLimit:      { requests: 10, windowMs: 60_000 },
    },
    {
      path:           '/api/**',
      require:        'ed25519',
      allowedSenders: ['agent.alpha', 'agent.beta'],
      rateLimit:      { requests: 100, windowMs: 60_000 },
    },
  ],
  defaultPolicy: 'deny',   // reject anything that doesn't match a policy above
  signResponses: true,
  privateKey:    gatewayPrivateKey,
  sender:        'gateway',
})

createServer(async (req, res) => {
  const chunks: Buffer[] = []
  for await (const chunk of req) chunks.push(chunk)
  const result = await gateway.handle({
    method:  req.method ?? 'GET',
    path:    req.url ?? '/',
    headers: Object.fromEntries(
      Object.entries(req.headers).filter(([, v]) => v !== undefined),
    ) as Record<string, string>,
    body: chunks.length ? Buffer.concat(chunks).toString('utf8') : undefined,
  })
  res.writeHead(result.status, result.headers)
  res.end(result.body)
}).listen(3000)

Use createProductionGateway() instead of createGateway() to fail fast at startup if defaultPolicy isn't 'deny' or replayStore isn't configured — a misconfiguration you want caught at deploy time, not discovered later in production.

Gateway architecture:

flowchart TB
    subgraph Inbound
        A[Agent Request\nx-7h3-envelope] --> B[Verify Signature]
        B --> C[Check TTL + Nonce]
        C --> D[Match Route Policy]
        D --> E[Rate Limit by Sender]
    end
    subgraph Upstream
        E -->|pass| F[Service\nx-7h3-sender: agent.alpha\nx-7h3-verified: true]
        E -->|deny| G[401 / 403 / 429]
    end
    subgraph Outbound
        F --> H[Sign Response\nx-7h3-response: sig]
        H --> A
    end

CLI gateway — a flag-based, single-policy gateway for quick use without writing code (see CLI Reference for the full flag list):

7h3 gateway --upstream http://localhost:3001 --port 3000 \
  --public-key <base64url-key> --sender agent.alpha --require ed25519

The CLI gateway supports one implicit sender/policy pair via flags — it does not read a YAML/JSON config file. For multi-policy setups (per-route allowedSenders, rate limits, mixed algorithms), use createGateway() directly as shown above.

Cloudflare Workers

cloudflare/ contains a complete Cloudflare Workers deployment — a cryptographic reverse proxy that enforces 7h3 signing on all inbound traffic, using KV for distributed key registry and nonce replay protection across all Cloudflare PoPs.

Caller ──[x-7h3-envelope]──▶ 7h3 Gateway Worker ──[clean + x-7h3-sender]──▶ Upstream
         Ed25519 signed         verify + strip                                 your Worker

One-command setup

cd cloudflare
npm install
npm run setup     # generates keypair, creates KV namespaces, stores secret

Then set UPSTREAM_URL in wrangler.toml and deploy:

npm run deploy:staging
npm run deploy:production

Middleware for existing Workers

Add 7h3 verification to any existing Worker without a full reverse-proxy setup:

import { create7h3Middleware } from './cloudflare/src/middleware'

export default {
  async fetch(request: Request, env: Env, ctx: ExecutionContext) {
    const mw = create7h3Middleware(env)
    const check = await mw.verify(request)
    if (!check.ok) return check.response   // 401 or 403

    // check.sender holds the verified agent identity
    return myHandler(request, env, ctx)
  },
}

What's included

File	Purpose
`cloudflare/src/worker.ts`	Standalone gateway entry point
`cloudflare/src/middleware.ts`	`create7h3Middleware()` for existing Workers
`cloudflare/src/kv-replay-store.ts`	KV-backed nonce dedup (cross-instance)
`cloudflare/src/kv-key-registry.ts`	KV-backed public key registry
`cloudflare/src/durable-replay.ts`	Durable Object for fully atomic replay
`cloudflare/wrangler.toml`	KV bindings, env vars, staging + production
`cloudflare/scripts/cf-setup.ts`	First-time setup automation
`cloudflare/DEPLOY.md`	Step-by-step deployment guide

Replay protection tiers

Store	Consistency	Setup
`KvReplayStore` (default)	Strong within datacenter, ~60ms global lag	KV namespace (free plan)
`DurableReplayStore`	Fully atomic, zero race window	Durable Objects (paid plan)

wrangler kv:key put --namespace-id <ID> \
  "7h3:pk:[email protected]" "<base64url-ed25519-spki-pubkey>"

Key discovery is served automatically at GET /.well-known/7h3-keys.

AI Coding Agents

7h3 Protocol ships first-class support for AI coding environments. Each tool reads its config automatically — no plugin installation required.

Tool	Config file	What it gets
Claude Code	`CLAUDE.md` + MCP server	Live keygen/sign/verify/scaffold tools + full repo context
GPT Codex	`AGENTS.md`	Full integration patterns, snippets, invariants
Opencode	`AGENTS.md`	Same
Grok Builder	`AGENTS.md`	Same

Claude Code — MCP server

Install the MCP server once to get live tools in every Claude Code session:

claude mcp add 7h3-protocol -- npx -y @7h3/protocol-mcp

Or copy .claude/settings.example.json → .claude/settings.json in your project.

Available MCP tools:

Tool	Description
`7h3_generate_keypair`	Generate an Ed25519 keypair
`7h3_generate_secret`	Generate a 32-byte HMAC secret
`7h3_sign`	Sign a test envelope for debugging
`7h3_verify`	Verify an envelope's signature, TTL, and shape
`7h3_scaffold`	Generate integration code for a framework — `cloudflare-worker`, `nextjs`, `express`, `hono`, `fastify`, `claude-code`, or `raw` (narrower than `7h3 add`'s list below)
`7h3_mcp_config`	Get install config for Claude Code, Cursor, Opencode, Grok
`7h3_wrap_mcp_server`	Generate boilerplate to wrap an MCP handler with 7h3

`7h3 add` — scaffold any project

Generate ready-to-paste integration code from the CLI:

# Framework integrations
npx 7h3 add --framework cloudflare-worker --sender [email protected]
npx 7h3 add --framework nextjs            --sender [email protected]
npx 7h3 add --framework express           --sender [email protected]
npx 7h3 add --framework hono              --sender [email protected]
npx 7h3 add --framework fastify           --sender [email protected]

# AI tool setup instructions
npx 7h3 add --framework claude-code
npx 7h3 add --framework opencode
npx 7h3 add --framework codex
npx 7h3 add --framework grok

# Write to a file
npx 7h3 add --framework hono --output middleware/7h3-auth.ts

When called from the MCP server, 7h3_scaffold does the same — Claude Code can call it directly and paste the result into your file.

MCP (Claude Tool Calls)

Claude's tool-calling mechanism is MCP (Model Context Protocol) — plain JSON-RPC 2.0. 7h3 Protocol hardens MCP traffic without any changes to your handler.

flowchart LR
    CA[Claude] -->|Signed JSON-RPC| MW[7h3 MCP Wrapper]
    MW -->|Verify sig\ncheck replay\nrecipient binding| MH[Your MCP Handler]
    MH -->|Response| MW
    MW -->|Sign response\ncorrelation binding| CA

Server side:

import { wrapMcpServer, signEnvelopeEd25519 } from '@7h3/protocol'

const secureServer = wrapMcpServer(myMcpHandler, {
  selfAgentId: 'my-mcp-server',
  sign: (e) => signEnvelopeEd25519(e, serverPrivateKey, 'k1'),
  receive: {
    signatureResolver: async (signature, senderId) =>
      ({ alg: 'ED25519', publicKey: clientPublicKeys[senderId] }),
  },
})

Client side:

import { wrapMcpClient, signEnvelopeEd25519 } from '@7h3/protocol'

const { send } = wrapMcpClient({
  selfAgentId: 'claude-agent',
  peerAgentId: 'my-mcp-server',
  sign: (e) => signEnvelopeEd25519(e, clientPrivateKey, 'k1'),
  receive: {
    signatureResolver: async () => ({ alg: 'ED25519', publicKey: serverPublicKey }),
  },
})

const result = await send({ jsonrpc: '2.0', id: 1, method: 'tools/list' }, fetch)

The MCP handler itself is unchanged — zero migration. The wrapper handles all envelope logic at the boundary.

End-to-End Encryption

Signing proves authenticity. Encryption proves privacy. sealEnvelope combines both: the body is encrypted before signing so it's opaque to any intermediary, and signature is verified before decryption so tampering fails fast.

Forward secrecy is automatic — a fresh ephemeral X25519 keypair is generated per message.

sequenceDiagram
    participant S as Alice (Sender)
    participant R as Bob (Receiver)

    S->>S: generateX25519KeyPair() → ephemeral keypair
    S->>S: ECDH(ephemeral_priv, bob_x25519_pub) → shared_secret
    S->>S: HKDF-SHA256(shared_secret, nonce) → encryption_key
    S->>S: ChaCha20-Poly1305(key, body) → ciphertext
    S->>S: Ed25519 sign(envelope with encrypted body)
    S->>R: Sealed envelope (ciphertext only, body invisible)
    R->>R: Verify Ed25519 signature FIRST
    R->>R: ECDH(bob_priv, ephemeral_pub) → shared_secret
    R->>R: HKDF → encryption_key
    R->>R: ChaCha20-Poly1305 decrypt + verify AEAD tag
    R->>R: Recover original body

Zero new dependencies — Node.js built-in crypto.ecdh + crypto.createCipheriv('chacha20-poly1305').

TypeScript:

import {
  generateX25519KeyPair,
  sealEnvelope,
  openEnvelope,
} from '@7h3/protocol'

// Each agent needs an Ed25519 signing keypair + an X25519 encryption keypair
const aliceSign = await generateEd25519KeypairBase64Url()
const aliceEnc  = generateX25519KeyPair()   // synchronous

const bobSign = await generateEd25519KeypairBase64Url()
const bobEnc  = generateX25519KeyPair()

// Alice seals a message for Bob
const envelope = createEnvelope('alice', { intent: 'TASK', content: 'secret payload' })

const sealed = await sealEnvelope(envelope, {
  recipientX25519PublicKey: bobEnc.publicKey,
  senderEd25519PrivateKey:  aliceSign.privateKey,
})
// sealed.body.intent === 'ENCRYPTED'
// sealed.body.content is the encrypted blob — opaque to any eavesdropper

// Bob opens it
const { body } = await openEnvelope(sealed, {
  recipientX25519PrivateKey: bobEnc.privateKey,
  senderEd25519PublicKey:    aliceSign.publicKey,
})
// body.content === 'secret payload'

Python:

from protocol_7h3.encryption import generate_x25519_keypair, seal_envelope, open_envelope

alice_enc_pub, alice_enc_priv = generate_x25519_keypair()
bob_enc_pub,   bob_enc_priv   = generate_x25519_keypair()

sealed = seal_envelope(envelope, bob_enc_pub, alice_sign_priv)
body   = open_envelope(sealed, bob_enc_priv, alice_sign_pub)

Go:

bobPub, bobPriv, _ := go7h3.GenerateX25519KeyPair()

sealed, _       := go7h3.SealEnvelope(env, bobPub, alicePriv)
env, body, _    := go7h3.OpenEnvelope(sealed, bobPriv, alicePub)

Capability Tokens and Delegation

Capability tokens let one agent grant another scoped, time-bounded, cryptographically verifiable authority — without sharing keys.

Example: service A grants service B permission to call /api/payments/** for 5 minutes. B can delegate a narrower scope to C. Any receiver can verify the full A → B → C chain.

flowchart LR
    A[Root Agent] -->|"issue(scope:/payments/**)"|B[Agent B]
    B -->|"delegate(scope:/payments/read)"| C[Agent C]
    C -->|"x-7h3-capability: [A→B token, B→C token]"| D[Gateway]
    D -->|"verifyChain"| E{Valid?}
    E -->|yes| F[Upstream]
    E -->|no| G[401]

Issue a token:

import { issueCapabilityToken } from '@7h3/protocol'

const token = await issueCapabilityToken({
  issuerPrivateKey: rootPrivateKey,
  issuerId:         'root-agent',
  subject:          'agent.worker',
  scopes: [
    { pathGlob: '/api/payments/**', methods: ['POST'], maxDelegations: 1 },
  ],
  ttlMs:          300_000,   // 5 minutes
  maxDelegations: 1,         // one more delegation hop allowed
})

Delegate a narrower scope:

import { delegateCapabilityToken } from '@7h3/protocol'

const delegation = await delegateCapabilityToken({
  parentToken:         token,
  delegatorPrivateKey: workerPrivateKey,
  delegatorId:         'agent.worker',
  newSubject:          'agent.subworker',
  scopes: [
    { pathGlob: '/api/payments/read', methods: ['GET'] },  // must be ⊆ parent
  ],
  ttlMs: 60_000,   // must not exceed parent's remaining TTL
})

Attach to HTTP request:

import { serializeCapabilityChain, CAP_HEADER } from '@7h3/protocol'

const headers = {
  [CAP_HEADER]: serializeCapabilityChain([token, delegation]),
  // x-7h3-capability: [base64-token-1, base64-token-2]
}

Verify a chain:

import { verifyCapabilityChain } from '@7h3/protocol'

const result = await verifyCapabilityChain(
  chain,
  { getPublicKey: async (id) => keyStore[id] },
  { requiredPathGlob: '/api/payments/read', requiredMethod: 'GET' }
)
// { ok: true, token, chain }  or  { ok: false, reason: '...' }

Streaming Message Signing

LLM outputs are streams of tokens. 7h3 Streaming Signing gives each chunk a per-chunk HMAC and seals the entire stream with a final Ed25519 signature over the full content hash. Clients detect tampering mid-stream.

sequenceDiagram
    participant LLM as Server
    participant C as Client

    LLM->>C: chunk 0: {i:0, d:"Hello ", h:HMAC0, f:false}
    LLM->>C: chunk 1: {i:1, d:"world", h:HMAC1, f:false}
    LLM->>C: chunk N: {i:N, d:".", h:HMACn, f:false}
    LLM->>C: final:   {i:N+1, d:"", h:HMAC_f, f:true, sig:Ed25519}

    C->>C: Verify HMAC on each chunk (tamper detected immediately)
    C->>C: Verify Ed25519 over full stream on final frame

Writing a signed stream:

import { SignedStreamWriter } from '@7h3/protocol'

const writer = new SignedStreamWriter({
  privateKey: serverPrivateKey,
  sender:     'llm.server',
  keyId:      'k1',
})

for await (const token of llmTokenStream) {
  const chunk = await writer.writeChunk(token)
  ws.send(JSON.stringify(chunk))
}
ws.send(JSON.stringify(await writer.finalize()))

Reading and verifying:

import { SignedStreamReader } from '@7h3/protocol'

const reader = new SignedStreamReader({ publicKey: serverPublicKey })

ws.on('message', async (raw) => {
  const chunk = JSON.parse(raw)
  if (!chunk.f) {
    const r = await reader.receiveChunk(chunk)
    if (!r.ok) throw new Error(`Chunk ${chunk.i} tampered: ${r.reason}`)
    appendToUI(chunk.d)
  } else {
    const result = await reader.finalize(chunk)
    if (!result.ok) throw new Error(result.reason)
    console.log(`Stream verified — ${result.chunkCount} chunks, ${result.totalBytes} bytes`)
  }
})

Convenience wrappers for complete arrays:

import { signStream, verifyStream } from '@7h3/protocol'

const chunks = await signStream(
  ['Hello ', 'world', '.'],
  { privateKey, sender: 'llm', keyId: 'k1' }
)

const result = await verifyStream(chunks, { publicKey })
// { ok: true, totalBytes: 12, chunkCount: 3 }

WebSocket integration:

import { createSignedWebSocketStream, receiveSignedWebSocketStream } from '@7h3/protocol'

// Server side
const writer = createSignedWebSocketStream(ws, { privateKey, sender: 'llm', keyId: 'k1' })   // synchronous

// Client side
const result = await receiveSignedWebSocketStream(ws, { publicKey })

Distributed Replay Cache (Redis)

The default in-memory replay cache breaks in multi-instance deployments. A replayed nonce can slip through between two gateway instances. Use RedisReplayStore in production.

import { createRedisReplayStore } from '@7h3/protocol'

const replayStore = createRedisReplayStore({ redisUrl: 'redis://localhost:6379' })

const gateway = createGateway({ ...opts, replayStore })

Redis Cluster (queries all nodes — a nonce is seen if ANY node has it):

import { createClusterReplayStore } from '@7h3/protocol'

const replayStore = createClusterReplayStore([
  'redis://node-1:6379',
  'redis://node-2:6379',
  'redis://node-3:6379',
])

Inject your own Redis client:

import { RedisReplayStore } from '@7h3/protocol'
import { createClient } from 'redis'

const client = createClient({ url: 'redis://localhost:6379' })
await client.connect()

const replayStore = new RedisReplayStore({ client })
// RedisClientLike: any client implementing set(k, v, opts) + get(k)
// Works with ioredis, redis, @upstash/redis

Python:

from protocol_7h3.replay import create_redis_replay_store

store = create_redis_replay_store('redis://localhost:6379')

Go:

store := go7h3.NewRedisReplayStore("7h3:nonce:", func(ctx context.Context, key string, ttl time.Duration) (bool, error) {
    return redisClient.SetNX(ctx, key, "1", ttl).Result()
})

Binary Wire Format (CBOR)

CBOR (RFC 8949 deterministic mode) produces ~40% smaller payloads compared to JSON. Uses numeric field keys for maximum compactness.

import { encodeEnvelopeCbor, decodeEnvelopeCbor, CBOR_CONTENT_TYPE } from '@7h3/protocol'

// Encode
const bytes: Uint8Array = encodeEnvelopeCbor(signedEnvelope)
// bytes.length ≈ 60% of JSON.stringify(signedEnvelope).length

// Decode
const envelope = decodeEnvelopeCbor(bytes)

// HTTP
await fetch(url, {
  method:  'POST',
  headers: { 'Content-Type': CBOR_CONTENT_TYPE },  // 'application/7h3-cbor'
  body:    bytes,
})

General-purpose CBOR (zero runtime deps):

import { encodeCbor, decodeCbor } from '@7h3/protocol'

const bytes = encodeCbor({ any: 'value', nested: [1, 2, 3], ok: true })
const value = decodeCbor(bytes)

Go:

bytes, err := go7h3.EncodeEnvelopeCBOR(env)
env, err   := go7h3.DecodeEnvelopeCBOR(bytes)

Observability (Prometheus + OpenTelemetry)

Prometheus Metrics

Zero new dependencies — implements the Prometheus exposition format from scratch.

import { metrics, renderPrometheusText, createMetricsMiddleware } from '@7h3/protocol'

// Serve /metrics on your existing Express app
app.use(createMetricsMiddleware('/metrics'))

// Or render manually
app.get('/metrics', (req, res) => {
  res.set('Content-Type', 'text/plain; version=0.0.4')
  res.send(renderPrometheusText(metrics))
})

Available metrics:

Metric	Type	Labels
`7h3_verifications_total`	counter	`result` (ok\|fail), `alg`, `transport`
`7h3_verification_duration_ms`	histogram	—
`7h3_rate_limit_hits_total`	counter	`sender`, `path`
`7h3_sender_denials_total`	counter	`sender`, `path`
`7h3_replay_detections_total`	counter	`transport`
`7h3_audit_entries_total`	counter	`type`
`7h3_active_connections`	counter	`transport`

CLI gateway:

7h3 gateway --upstream http://localhost:3001 --metrics-port 9090
# http://localhost:9090/metrics

OpenTelemetry

No hard dependency — inject any OTel-co

7h3 Protocol

At a glance

README

Table of Contents

The Problem

What 7h3 Protocol Does

How It Works

Canonical Serialization

Envelope Structure

End-to-End Flow

TTL and Nonce

Security Guarantees

Installation

TypeScript / Node.js

Python

Rust

Go

Browser

Post-Quantum Extension

Threshold Signatures Extension

Quick Start

Core API

Key Generation

Creating Envelopes

Signing

Verifying

Transports

HTTP / REST

WebSocket

gRPC

Message Queues

Webhooks

Gateway

Cloudflare Workers

One-command setup

Middleware for existing Workers

What's included

Replay protection tiers

AI Coding Agents

Claude Code — MCP server

7h3 add — scaffold any project

MCP (Claude Tool Calls)

End-to-End Encryption

Capability Tokens and Delegation

Streaming Message Signing

Distributed Replay Cache (Redis)

Binary Wire Format (CBOR)

Observability (Prometheus + OpenTelemetry)

Prometheus Metrics

OpenTelemetry

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