Local-first meeting notetaker. On-device transcription, no stored audio, E2E encrypted sync

Nod is currently under testing, so some technical issues may arise. Users are encouraged to report any problems they encounter. A conversation within Nod is transformed into four distinct types of data: the audio, the transcript, the notes, and the encryption keys. This application is designed to keep only one type of data off the user's device, and that single piece of data remains unreadable by anyone else.

The audio data is only kept in memory as long as the speech model requires it. Once the meeting ends, the remaining audio is discarded. The transcript and notes, however, are saved on the user's device in encrypted files, with each meeting having its own file. The encryption keys are stored securely in the device's keychain. The vault key, which encrypts the files for synchronization, exists as a separate 256-bit key written as twenty-four BIP39 words.

This key is never sent to a server. Each device derives the vault key from the twenty-four words of the recovery phrase. If a device is lost, the vault key can be recovered using the recovery phrase. Nod uses AES-256-GCM, a strong authenticated encryption standard, to secure each meeting. The encrypted file starts with a version byte and a random 96-bit nonce.

The ciphertext and a 128-bit tag follow. Each meeting is bound to its encryption key in the tag as associated data, ensuring that an encrypted file from one meeting cannot be opened in another. The file key is a random 256-bit key, wrapped by the operating system's keychain. This key wraps the vault key for synchronization purposes.

Nod facilitates sharing meetings through a location chosen by the user, such as a folder in existing file sync services or a relay server. The location only contains encrypted files, without any information that could potentially expose the file contents. The vault key is never transmitted to a server. Each device generates the vault key independently from the recovery phrase.

A phone can acquire the vault key by scanning a QR code carrying a one-time pairing secret. Each meeting is represented as an Automerge document, allowing multiple devices to edit the same meeting simultaneously without the risk of losing any edits. Conflicts are resolved, and deleting a meeting results in a deletion recorded on all devices.

Nod is supported on macOS and Windows, with plans to release a version for Linux. The application is signed by the developer's Apple Developer ID on macOS and undergoes notarization by Apple. Windows users will see a warning when running Nod for the first time, indicating that the developer has not yet obtained a code signing certificate.

Nod provides SHA256 hash values for each release file in a SHA256SUMS file, which is signed with the developer's release key. Before installing a new release, Nod verifies the file hashes against the signed list to ensure the file's integrity.