DID:PLC Rotation Keys: How the 72-Hour Recovery Window Works

DID:PLC uses a sophisticated key rotation system. Every account has 1-5 rotation keys that control the identity. Understanding how these keys work is essential for securing your ATProto account.

Key Types and Priority

DID:PLC supports two elliptic curve algorithms:

• secp256k1 (Bitcoin/Ethereum curve)
• P-256 (NIST standard, YubiKey compatible)

Keys are stored in priority order. Index 0 has the highest authority. Lower index means higher authority.

A typical setup:

rotationKeys[0] = your offline backup key (highest priority)
rotationKeys[1] = your PDS operational key (lower priority)

Any key can sign operations. But higher-priority keys can override operations signed by lower-priority keys.

The 72-Hour Recovery Window

This is the core security mechanism.

When an operation is accepted by the PLC directory, a 72-hour clock starts. During this window, a higher-priority key can submit a recovery operation that forks from before the malicious change, effectively nullifying it.

After 72 hours, operations become final.

How Recovery Works

Scenario: Your PDS goes rogue and removes your backup key.

• PDS submits operation removing your key
• You detect this within 72 hours
• You sign a new operation with your backup key (higher priority)
• Your operation points to the state before the attack
• PLC directory accepts your operation and nullifies the PDS's change

The math is simple: if your key has a lower index than the attacker's key, and you act within 72 hours, you recover.

Practical Security

Adding your own rotation key:

const creds = await agent.com.atproto.identity.getRecommendedDidCredentials();
const { token } = await agent.com.atproto.identity.requestPlcOperationSignature();

await agent.com.atproto.identity.signPlcOperation({
  token,
  rotationKeys: [
    'did:key:zQ3sh...YourKey',  // Your key first (highest priority)
    ...creds.rotationKeys        // Existing keys
  ]
});

Storage options:

• YubiKey (P-256) - keys never leave hardware
• Cold storage - air-gapped, metal/paper backup
• Password manager - convenient, lower security

Best practice: Your highest-priority key should never be online.

Monitoring

Monitor your DID for unauthorized changes:

# urlwatch config
url: "https://plc.directory/did:plc:your_did/log/audit"
filter:
  - diff: true
  - shell: "jq '.[-1]'"

Or use the firehose:

firehose.on('identity', (event) => {
  if (event.did === 'did:plc:your_did') {
    sendAlert(event);
  }
});

Attack Scenarios

PDS compromised:

• If you have a higher-priority key: recoverable within 72 hours
• If PDS key is highest priority: irrecoverable

Rotation key leaked:

• If you have other secure keys: rotate out the leaked key within 72 hours
• If all keys leaked: account compromised

PLC directory malicious:

• Cannot forge signatures
• Can reject operations (DoS)
• Can serve wrong forks
• Mitigation: use read replicas

Key Takeaways

• Always add your own rotation key at index 0
• Store that key offline or in hardware
• Monitor your DID for changes
• You have 72 hours to recover from most attacks
• After 72 hours, you're stuck with whatever changes were made

The 72-hour window is your safety net. Use it wisely.