Privacy Policy

1. Core Philosophy

Tether is engineered with a Zero-Knowledge Cloud architecture. We believe your physiological data is yours alone. We encrypt everything leaving your device so that not even we, the developers, can read it.

2. HealthData Collection & Apple HealthKit

• We request explicit permission via Apple HealthKit to read **Sleep Analysis, Sleep Heart Rate, and Respiratory Rate**.
• We do not write or overwrite any HealthKit data.
• We do not use your HealthKit data for marketing, advertising, or selling to third parties.

3. End-to-End Encryption (E2EE)

All your daily sleep metrics are locked in an encrypted envelope on your iPhone using Curve25519 cryptography. Our cloud backend simply routes these encrypted envelope blobs to your designated partner or your authorized local AI server. The private keys needed to decrypt this data never leave the Apple ecosystem and are synced securely via your personal iCloud Keychain.

4. Partner Syncing and Local AI (MCP)

• Partner Sharing: Encrypted data is only shared when you generate an invite code and explicitly establish a trust bond with your partner.
• Local AI Servers: When you scan a QR code to bind an MCP server, data flows directly to that specific machine for strictly local AI interaction.
• You can instantly revoke either consent path at any time in your Settings.

5. Account Metadata

To provide the routing service, we must retain a minimal amount of non-health metadata. This includes device IDs, server token hashes, relationship mappings, and request rate-limiting metrics required for security.