Under the Hood of ZeroText: Double Ratchet Cryptography & Zero Phone Exposure

The Cryptographic Primitives

ZeroText was engineered from the ground up to achieve what traditional messaging systems could not: complete zero-knowledge isolation combined with instant peer discovery.

1. The 8-Character Cryptographic PIN

Traditional apps ask for your phone number to populate their social graph. ZeroText derives an 8-character base-32 alphanumeric PIN directly from the SHA-256 fingerprint of your public identity key:

Master Seed (BIP-39) -> Ed25519 Keypair -> SHA256(PublicKey) -> Base32 Fingerprint (ZT-XXXXXX)

Because this PIN is mathematically bound to your public signature key, impersonation is cryptographically impossible.

2. Double Ratchet Session Management

Every conversation session maintains two synchronized ratchets: - KDF Chain Ratchet (Symmetric): Advances with every single message sent or received. - Diffie-Hellman Ratchet (Asymmetric): Advances whenever a response turn occurs, generating new ephemeral X25519 keypairs.

This guarantees both Forward Secrecy (compromise of today's key does not decrypt yesterday's messages) and Future Secrecy / Break-in Recovery (compromise of today's key does not allow decrypting tomorrow's messages once a new DH turn completes).

3. Volatile RAM WebSocket Relay

Unlike cloud providers that store message queues on persistent NVMe disks, ZeroText relay nodes operate strictly in volatile RAM. No message payload is ever committed to disk storage. Once the recipient device sends an authenticated delivery confirmation receipt, the memory buffer is wiped.