# Namespace EchoHub.Core.Security | EchoHub Documentation

# Namespace EchoHub.Core.Security

### Classes

RoomCrypto

  Client-side envelope encryption for private (end-to-end encrypted) channels.

  Design: at creation the client generates a random 256-bit room content key (RCK) that encrypts all room content. The RCK is stored on the server wrapped (AES-GCM encrypted) by a key derived from the passphrase, next to a BCrypt hash of a separately derived auth key used as the join gate. The passphrase, the key-encryption key, and the RCK never leave the client, so the server can gate joins and count/measure content without being able to read it. Changing the passphrase only re-wraps the RCK — history is never re-encrypted.

  Derivation: PBKDF2-SHA256(passphrase, salt, 210000 iterations) → 64 bytes; first 32 bytes are the auth key (sent to the server as lowercase hex), last 32 bytes are the key-encryption key (never sent).

RoomCrypto.DerivedKeys