NETTRASH.Exchange

Exchange is a cryptographic messenger that puts you in charge of your keys. Type your message in Exchange, encrypt it to a recipient whose public key you have saved, and you get a single line of encrypted text — an EXC2 envelope. Send it through any app you already use: iMessage, Mail, Telegram, WhatsApp, anything that can carry text. The recipient opens it back in Exchange and reads the original message. Nobody else can. Or use the built-in iMessage extension. Tap Exchange in the iMessage app drawer, pick a contact, type, encrypt, send. A locked-message bubble drops into the conversation. The recipient taps it and Exchange opens straight to the decrypted plaintext — no copy-paste, no app switching. NEW IN 1.1 Native Mac support. Exchange now runs as a Mac Catalyst app on Apple silicon and Intel Macs, sharing the same recipient list and decrypt flow as the iPhone version. Decrypt on tap from Messages. Tap a locked-message bubble in iMessage on iPhone or Mac and Exchange opens directly to the plaintext via Universal Links — no copy-paste. Rich link previews. Encrypted messages sent from the Compose flow now appear as preview bubbles in iMessage, Telegram, Slack, and other messengers, with the Exchange icon and an "Install Exchange" page for recipients without the app. Identity sync. By default, your private key is carried across the devices signed into your Apple ID via iCloud Keychain — which is itself end-to-end encrypted with a device-class secret. Toggle off in Settings if you prefer the original device-only behaviour. Recipients sync. Your saved recipient list is also kept in sync across your devices, encrypted on-device with a key derived from your identity. Apple sees only opaque ciphertext — display names, public keys, and notes stay end-to-end encrypted between your devices. Backup and transfer. In Settings, export your identity as a passphrase-encrypted blob you can save in a password manager, or transfer it in person to another of your devices via a single-use QR code. EVERYTHING ON YOUR DEVICE Exchange has no servers. No backend, no accounts, no telemetry, no analytics, no tracking. The cryptographic operations all run locally using Apple's CryptoKit framework. The only data that ever leaves your device is what you explicitly choose to send — and even then, only the encrypted envelope. PROVEN ALGORITHMS Exchange uses standard, publicly-vetted cryptography: - Curve25519 (X25519) key agreement - Ed25519 signatures for sender authentication - ChaCha20-Poly1305 authenticated encryption - HKDF-SHA256 for key derivation - PBKDF2-HMAC-SHA256 for passphrase backup Every message is signed by your identity and verified by the recipient before the plaintext is shown. Tampered envelopes are rejected, not silently corrupted. KEY EXCHANGE THAT MAKES SENSE Two people meet in person — at the office, at a cafe, at a conference. One taps "Show QR code" in Exchange, the other taps "Scan QR" from Add Recipient. A few seconds and they've exchanged the public-key bundle, including a fingerprint they can verify out loud. From then on, no matter what messenger they use to talk, only they can read what they send. WHAT EXCHANGE IS NOT Exchange isn't a chat app. It doesn't have group chats, voice calls, or read receipts. It's a tool you use with whatever transport you prefer. It isn't a key recovery service. If you lose all your devices and don't have iCloud Keychain sync turned on, your identity is gone. There is no developer-side recovery, no master key, no back door. It isn't a server-trust system. There's no central directory of users. You decide who your contacts are, in person or through whatever channel you trust. REQUIREMENTS iOS 26 or later on iPhone and iPad. macOS 26 or later on Mac (Apple silicon or Intel) via Mac Catalyst. Camera optional, used for QR-code scanning. FREE AND OPEN Exchange is independent software that respects your time and your data. No ads, no subscriptions, no upsells.