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IotaPolis

Encrypted Messaging

IotaPolis supports private direct messaging (DM) between users. All messages are end-to-end encrypted — the server relays ciphertext but cannot read your conversations.

How E2E Encryption Works

Key Exchange

IotaPolis uses X25519 Diffie-Hellman key exchange to establish shared secrets between users:

  1. Each user’s Ed25519 signing key is converted to an X25519 key pair
  2. When user A wants to message user B, the frontend computes a shared secret using A’s X25519 private key and B’s X25519 public key
  3. Both sides derive the same shared secret independently (Diffie-Hellman property)
  4. The shared secret is used to derive an AES-256-GCM encryption key

Message Encryption

Each message is encrypted with AES-256-GCM:

  • A unique initialization vector (IV) is generated per message
  • The message plaintext is encrypted with the shared AES key
  • The ciphertext + IV are stored on-chain via a FORUM_DM event
  • Only the sender and recipient can decrypt the message

What the Server Sees

The backend indexes DM events but only stores:

  • Sender address
  • Recipient address
  • Encrypted ciphertext
  • Timestamp

The server cannot read message contents. Even if the database is compromised, messages remain encrypted.

Sending a Message

  1. Navigate to a user’s profile and click Send Message, or go to the Messages page
  2. Type your message in the composer
  3. Click Send — the frontend encrypts the message and submits it as a blockchain transaction
  4. The recipient sees the message in their Messages page and receives a notification

Security Considerations

  • Forward secrecy: Each conversation uses a derived key from the X25519 exchange. Compromising one key does not expose other conversations.
  • No server trust: The server never sees plaintext. Key exchange happens entirely in the browser.
  • On-chain persistence: Encrypted messages are stored as blockchain events, making them censorship-resistant and auditable (but unreadable without keys).
  • Key backup: Your messaging keys are derived from your wallet mnemonic. Backing up your 12-word mnemonic backs up your messaging capability.