Addressing

A KeyPears address has the form name@domain — intentionally identical to an email address. The protocol places no restrictions on the local part beyond what email itself allows. An organization with existing email addresses can use the same addresses for KeyPears without any changes.

Identity model

Each user holds one or more sets of four key pairs:

• Ed25519 — classical signing (32-byte public key)
• X25519 — classical Diffie-Hellman (32-byte public key)
• ML-DSA-65 (FIPS 204) — post-quantum signing (1,952-byte public key)
• ML-KEM-768 (FIPS 203) — post-quantum key encapsulation (1,184-byte public key)

The most recent keys are the active keys. Signatures use composite Ed25519 + ML-DSA-65 (both must verify). Encryption uses hybrid X25519 + ML-KEM-768 (both shared secrets are combined via HKDF-SHA-256). Users may rotate keys freely, up to 100 per account. Old keys are retained so that messages encrypted under previous keys can still be decrypted.

All four private keys (Ed25519 signing key, X25519 private key, ML-DSA signing key, and ML-KEM decapsulation key) are encrypted client-side with AES-256-GCM under the user's encryption key and stored on the server as ciphertext. The server cannot decrypt them.

Domain ownership

Identity is bound to domain ownership. An address like alice@acme.com survives changes in hosting provider: if acme.com migrates from one KeyPears server to another, Alice's address and identity remain valid. Only the keypears.json configuration file is updated.

The server currently hosting a domain is trusted to publish the current public keys for addresses on that domain. KeyPears keeps this authority model simple on purpose so the protocol can be embedded in many applications. If you do not trust a hosted server to publish honest keys, host the domain yourself.

This contrasts with centralized systems where your address is controlled by the service provider (Signal's phone numbers, Keybase's usernames). With KeyPears, if you own your domain, you own your identity.

Comparison with other systems

KeyPears is the only federated encrypted communication system that uses the standard email address format. Your email address can be your KeyPears address.