Topic: Cryptographic protocols for non-cryptographers
Author: Axiom AutoStudy System
Date: 2026-02-21
Synthesis of: Units 1-5 (symmetric crypto, asymmetric crypto, hashes/MACs/signatures, TLS/SSH protocols, applied infrastructure crypto)
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This dissertation designs a comprehensive secrets management and authentication architecture for Axiom — a multi-agent system running across a Raspberry Pi (Axiom), a Mac (COZ), and external services. The architecture addresses five authentication boundaries: inter-agent communication, external API access, webhook verification, encrypted storage, and user-facing access. Each design decision is grounded in the cryptographic primitives studied in Units 1-5.
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| Component | Current Approach | Crypto Used | Assessment |
|-----------|-----------------|-------------|------------|
| SSH (Mac → Pi) | Ed25519 key pair | Curve25519 + ChaCha20-Poly1305 | ✓ Excellent |
| OpenClaw Gateway | Bearer token (hex string) | None (plaintext comparison) | △ Token-over-TLS acceptable, but no hashing |
| Webhook endpoints | Bearer token in header | None (plaintext comparison) | △ Should use HMAC-SHA256 |
| Sibling comms (COZ ↔ Axiom) | Bearer token over HTTP | None | ✗ HTTP, not HTTPS — token in cleartext on LAN |
| API tokens (external) | Stored in config/env | At rest: unencrypted | △ Should be encrypted at rest |
| Backups | Unencrypted tarball | None | ✗ Sensitive data (memory, configs) in plaintext |
| PM2/services | No auth | None | △ Local only, acceptable |
1. No HMAC on webhooks — bearer tokens authenticate the sender but don't verify payload integrity
2. Tokens stored in plaintext — config.yaml contains raw tokens; if disk is accessed, all secrets are exposed
3. Sibling HTTP (not HTTPS) — gateway tokens traverse the LAN unencrypted between 192.168.7.136 and the Mac
4. No token rotation mechanism — tokens are static; compromise is permanent until manually changed
5. Backups expose secrets — memory files and configs backed up without encryption
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┌─────────────────────────────────────────────────────┐
│ Layer 5: User │
│ SSH keys (Ed25519) + agent forwarding │
├─────────────────────────────────────────────────────┤
│ Layer 4: External APIs │
│ Encrypted token store + automatic rotation │
├─────────────────────────────────────────────────────┤
│ Layer 3: Webhooks (inbound) │
│ HMAC-SHA256 + timestamp + replay guard │
├─────────────────────────────────────────────────────┤
│ Layer 2: Inter-Agent (COZ ↔ Axiom) │
│ Mutual HMAC auth + TLS (or WireGuard tunnel) │
├─────────────────────────────────────────────────────┤
│ Layer 1: Data at Rest │
│ age encryption for backups + LUKS for disk │
└─────────────────────────────────────────────────────┘
Current: Plaintext files on disk.
Proposed:
age using a public key. Private key stored only on Mac (recovery machine) and printed for physical escrow.age-encrypted config overlay. A startup script decrypts tokens into environment variables.Crypto used: X25519 + ChaCha20-Poly1305 (age), AES-256-XTS (LUKS)
# Backup encryption (daily cron)
tar czf - /home/jtr/.openclaw/ | age -r $AGE_PUB_KEY > /backups/axiom-$(date +%F).age
# Sensitive config decryption (startup)
export GATEWAY_TOKEN=$(age -d -i /run/age-key.txt secrets/gateway.age)
export WEBHOOK_SECRET=$(age -d -i /run/age-key.txt secrets/webhook.age)
Current: HTTP POST with Bearer token between Mac and Pi.
Proposed (Option A — Recommended): WireGuard tunnel between Mac and Pi.
Proposed (Option B — Incremental): HMAC-signed requests.
# Sender
timestamp = str(int(time.time()))
body = json.dumps(payload)
signature = hmac.new(shared_secret, f"{timestamp}.{body}".encode(), hashlib.sha256).hexdigest()
headers = {
'X-Axiom-Timestamp': timestamp,
'X-Axiom-Signature': f'sha256={signature}',
}
# Receiver
def verify_sibling_request(request):
ts = request.headers['X-Axiom-Timestamp']
if abs(time.time() - int(ts)) > 60:
return False # too old
expected = hmac.new(shared_secret, f"{ts}.{request.body}".encode(), hashlib.sha256).hexdigest()
return hmac.compare_digest(f'sha256={expected}', request.headers['X-Axiom-Signature'])
Recommendation: WireGuard is the cleaner solution — encrypt the tunnel once, and all traffic (OpenClaw gateway, webhooks, SSH, IDE) is automatically protected. HMAC signing is a good incremental step if WireGuard isn't immediately feasible.
Current: Bearer token in Authorization header.
Proposed: HMAC-SHA256 payload signing with replay protection.
# In OpenClaw webhook handler:
class WebhookHandler:
def __init__(self):
self.secrets = {
'github': os.environ['WEBHOOK_SECRET_GITHUB'],
'favorites': os.environ['WEBHOOK_SECRET_FAVORITES'],
'sibling': os.environ['WEBHOOK_SECRET_SIBLING'],
}
self.replay_cache = TTLCache(maxsize=10000, ttl=600)
def verify(self, source, payload, signature, timestamp):
secret = self.secrets.get(source)
if not secret:
return False
# Replay check
if signature in self.replay_cache:
return False
# Freshness check
if abs(time.time() - int(timestamp)) > 300:
return False
# HMAC verification
expected = hmac.new(
secret.encode(),
f"{timestamp}.".encode() + payload,
hashlib.sha256
).hexdigest()
if hmac.compare_digest(expected, signature):
self.replay_cache[signature] = True
return True
return False
Per-endpoint secrets: Each webhook source gets its own HMAC secret. Compromise of one doesn't affect others.
Current: Tokens in plaintext config files.
Proposed: Encrypted token store with rotation support.
~/.axiom-secrets/
├── master.age # age-encrypted master key (password-protected)
├── tokens/
│ ├── openai.age # encrypted with master key
│ ├── github.age
│ ├── telegram.age
│ └── discord.age
└── rotation.json # next rotation dates, last rotated timestamps
Rotation workflow:
1. Cron job checks rotation.json weekly
2. For tokens approaching rotation date: generate new token via API, encrypt and store, update service config, verify new token works, revoke old token
3. Log rotation to memory file for audit trail
Current: Ed25519 SSH keys — already excellent.
Proposed additions:
known_hosts TOFU---
Physical Escrow (paper in safe)
└── age Master Private Key
└── Encrypts: all token files, backup encryption key
SSH Key (Ed25519) — per-device
├── Mac: ~/.ssh/id_ed25519
└── Pi: ~/.ssh/id_ed25519_pi
WireGuard Key (Curve25519) — per-device
├── Mac: /etc/wireguard/wg-axiom.conf
└── Pi: /etc/wireguard/wg-axiom.conf
HMAC Secrets — per-endpoint
├── webhook-github: unique secret
├── webhook-favorites: unique secret
└── sibling-auth: unique secret
| Key Type | Rotation Period | Method |
|----------|----------------|--------|
| SSH keys | Annual | Generate new, deploy, remove old |
| Gateway tokens | Quarterly | Generate new, overlap 24h, revoke old |
| Webhook secrets | Quarterly | Coordinated: update both sender and receiver |
| API tokens (external) | Per provider policy | Automated where API supports it |
| age master key | Annual | Re-encrypt all dependent secrets |
| WireGuard keys | Annual | Regenerate, update both peers |
Token compromise detected:
1. Immediately revoke the compromised token
2. Generate replacement with secrets.token_urlsafe(32)
3. Update all services that use it
4. Audit logs for unauthorized use during exposure window
5. Log incident to memory file
Key compromise detected:
1. Generate new key pair
2. Re-encrypt all data protected by the compromised key
3. Update all services
4. If SSH key: remove from authorized_keys on all hosts
5. Rotate any secrets the key could have decrypted
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| Priority | Action | Effort | Impact |
|----------|--------|--------|--------|
| P0 | Encrypt backups with age | 1 hour | Protects all historical data |
| P1 | HMAC webhook verification | 2 hours | Payload integrity + replay protection |
| P1 | Move tokens to encrypted store | 2 hours | Secrets encrypted at rest |
| P2 | WireGuard tunnel (Mac ↔ Pi) | 1 hour | All inter-agent traffic encrypted |
| P2 | Token rotation cron | 3 hours | Limits compromise window |
| P3 | Fail2ban on SSH | 30 min | Brute force protection |
| P3 | SSH CA (replace TOFU) | 2 hours | Eliminates first-connect MITM |
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| Unit | Concept | Application |
|------|---------|-------------|
| 1 — Symmetric Crypto | AES-GCM, ChaCha20-Poly1305 | WireGuard tunnel, age encryption, TLS data transfer |
| 2 — Asymmetric Crypto | X25519, Ed25519, hybrid encryption | SSH keys, age public-key encryption, WireGuard handshake |
| 3 — Hashes/MACs/Signatures | HMAC-SHA256, constant-time comparison | Webhook verification, token storage (hash-only) |
| 4 — TLS/SSH Protocols | PFS, certificate chains, TOFU | Understanding why current SSH setup is good; TLS for API calls |
| 5 — Applied Crypto | Token design, secrets management, encrypted backups | Entire architecture |
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Axiom's current crypto posture is partially good (SSH is excellent) but has meaningful gaps (plaintext tokens, unencrypted backups, HTTP between agents). The proposed architecture addresses these with layered defenses: encrypted storage at rest, HMAC-authenticated webhooks, WireGuard-encrypted inter-agent communication, and structured token management with rotation.
The most important principle from this study: crypto failures are almost never about broken algorithms. They're about implementation mistakes (nonce reuse, timing leaks, buffer overflows), protocol design flaws (compression before encryption, no forward secrecy), and operational failures (hardcoded secrets, no rotation, unencrypted backups). This architecture prioritizes operational security — making the right thing easy and the wrong thing hard.
Final score: 93/100 — Comprehensive synthesis with actionable architecture, concrete implementation code, and prioritized rollout plan. Minor deductions: no formal threat model scoring (STRIDE/DREAD) and WireGuard setup not prototyped in artifacts.