Echoes

Offline-first, end-to-end encrypted notes — synced privately over Nostr, on your terms.

Echoes is a Flutter notes app for Android and Linux/Windows desktop that treats the network as optional. Every note, checklist, image, and voice memo is saved locally first and stays fully usable with no connection at all. Nothing is ever published without an explicit opt-in: a note only starts syncing after you sync it once yourself — from then on, that note's updates ride the background sync (on launch, periodically, and on reconnect), while everything else stays local-only. Everything that leaves the device is encrypted before it goes: note content is NIP-44 self-encrypted, and image/voice attachments are AES-256-GCM encrypted client-side before upload, so relay operators and file hosts only ever see opaque ciphertext.

Features Offline-first — notes are always readable/writable locally; nothing blocks on network or relay availability. Private Nostr sync — per-note or bulk, explicit opt-in. Content is NIP-44 self-encrypted and published as a parameterized-replaceable event (NIP-78/33), so edits update the same event in place instead of piling up duplicates. Share notes with other Nostr users — end-to-end encrypted, one NIP-44 copy per recipient (so revoking access actually cuts someone off). Recipients can edit; their changes sync back to the owner and merge. Add recipients by npub, hex, or a NIP-05 identifier (name@domain), with contact autocomplete and an avatar-and-name confirmation before anything is shared. Encrypted attachments — images and voice notes are AES-256-GCM encrypted on-device, then uploaded to a Blossom or NIP-96 file host. The host never sees the plaintext, filename, or media type in the clear. Diary mode — journal-style entries tagged with a date (defaults to today, freely backdated/postdated), shown as a day-grouped timeline separate from regular notes. Optional at-rest encryption — password-protect the local note database (PBKDF2 + AES-256-GCM); the password is never stored. Flexible sign-in — import a private key directly, delegate to Amber (NIP-55 external signer, Android), or connect a NIP-46 remote signer ("bunker", every platform) so the private key stays in the signer and never reaches Echoes. Bring your own infrastructure — any relay (including a self-hosted one over ws:// on a local network or Tailscale) and any Blossom/NIP-96 host; built-in defaults were chosen specifically for not rejecting encrypted uploads. Adding a relay auto-republishes your already-synced notes to it. Backup by relay, not by cloud — export/import notes as a (optionally password-encrypted) JSON file, or republish everything to a newly added relay to backfill it. Checklists, voice notes, inline images — with a lightweight markdown formatting toolbar (bold/italic/heading/list/link) and a read-view/edit-view split, so opening a note shows a clean rendered view first. Google-Keep-style post-it grid (default) or single-column list, light/dark themes, and 27 languages (all 24 official EU languages plus Chinese, Japanese and Russian).