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All messages in Hoot are encrypted using NIP-59 gift wrapping, a sophisticated encryption scheme that provides forward secrecy and hides metadata about who is communicating.

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NIP-59 gift wrapping

NIP-59 (Nostr Implementation Possibility 59) is a privacy-preserving encryption standard that wraps messages in multiple layers of encryption. Unlike simple end-to-end encryption, gift wrapping:
  • Hides sender and recipient: Relays only see encrypted envelopes
  • Provides forward secrecy: Uses ephemeral keys that can’t be reused
  • Protects metadata: Timestamps and other details are obscured
The process involves two layers:
  1. Seal: Inner layer encrypted to the recipient
  2. Gift wrap: Outer layer (kind 1059) with randomized metadata
Gift wrapping is the default for all Hoot messages. You don’t need to enable it—every message you send is automatically encrypted.

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How messages are encrypted

When you send a message in Hoot, the encryption happens in multiple steps:

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Step 1: Create the mail event

First, Hoot creates a kind 2024 event with your message content, recipients, and subject. This event is called a “rumor” because it doesn’t have a signature yet.

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Step 2: Wrap per recipient

Each recipient gets their own encrypted copy. From src/mail_event.rs:59-68: 
let mut event_list: HashMap<PublicKey, Event> = HashMap::new();
for pubkey in pubkeys_to_send_to {
    let wrapped_event =
        EventBuilder::gift_wrap(sending_keys, &pubkey, base_event.clone(), None)
            .block_on()
            .unwrap();
    event_list.insert(pubkey, wrapped_event);
}
If you send a message to 5 people, Hoot creates 5 separate gift-wrapped events—one encrypted for each recipient. This ensures that relays can’t determine who else received the message.

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Step 3: Send to relays

Each encrypted event is sent to all connected relays. The relays only see:
  • A kind 1059 event (gift wrap)
  • A recipient public key tag
  • Random timestamp (obscured for privacy)
  • Encrypted payload
Relays cannot read the message content, subject, or sender information.

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Receiving encrypted messages

When Hoot receives a kind 1059 event from a relay, it attempts to decrypt it:

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Unwrapping process

From src/event_processing.rs:368-394: 
match app.account_manager.unwrap_gift_wrap(&event) {
    Ok(unwrapped) => {
        if unwrapped.sender != unwrapped.rumor.pubkey {
            warn!("Gift wrap seal signer mismatch for event {}", event.id);
            return;
        }

        let mut rumor = unwrapped.rumor.clone();
        rumor.ensure_id();
        if let Err(e) = rumor.verify_id() {
            error!("Invalid rumor id for gift wrap {}: {}", event.id, e);
            return;
        }
        // ... store the unwrapped event
    }
}
The unwrapping process:
  1. Checks recipient: Verifies you have the private key to decrypt
  2. Decrypts seal: Extracts the inner sealed event
  3. Validates sender: Ensures the seal was created by the claimed sender
  4. Verifies rumor ID: Confirms the inner event is valid
  5. Stores rumor: Saves the decrypted mail event to the database
Hoot stores the decrypted rumor (kind 2024 event) in the database, not the encrypted gift wrap. This allows for efficient searching and threading while maintaining privacy.

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Gift wrap storage

While the decrypted content is stored for display, Hoot also maintains a mapping between:
  • The gift wrap event ID (encrypted envelope)
  • The inner rumor event ID (decrypted message)
  • The recipient who received this copy
This mapping is important for:
  • Deletion requests: When a sender deletes a message, Hoot can identify which gift wraps to mark as deleted
  • Multi-device sync: Different devices may receive different encrypted copies
  • Privacy protection: Ensures gift wraps aren’t unnecessarily decrypted multiple times

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Multiple accounts

Hoot supports multiple keypairs in the same application. From CLAUDE.md:49:
AccountManager coordinates key loading, generation, and gift-wrap decryption
When a gift-wrapped event arrives, Hoot tries to decrypt it with all loaded keys. If any key successfully decrypts the message, it’s stored and displayed in the inbox. This allows you to:
  • Check multiple email identities in one app
  • Receive messages sent to any of your public keys
  • Switch between accounts without losing messages
Each account’s private keys are stored securely using platform-specific key storage (Keychain on macOS, Secret Service on Linux, Credential Manager on Windows).