OTRx vs ZIØN

OTRx-SDM is a private messaging app built for people who want conversations to feel truly “off the record”. Send self-destructing text messages that are end-to-end encrypted and automatically disappear after a short time, so your words don’t live forever on someone else’s phone. PRIVACY-FIRST, OFF-THE-RECORD CHATS • One-to-one text messaging with disappearing messages • Multiple privacy levels with different expiry timers • No media uploads – text only for a focused, low-risk experience • No ads, public profiles, or social discovery features END-TO-END ENCRYPTED & EPHEMERAL All chats are protected with end-to-end encryption between devices. We do not keep a permanent copy of user conversations. Messages are stored only in encrypted form and are removed once their selected timer has expired, so past chats are designed to disappear from both sides. SELF-DESTRUCTING MESSAGES Choose how long each message stays visible. A timer bar shows the remaining time and the selected privacy level. When the timer runs out, the message is cleared, helping you reduce the digital trace of your private conversations. Message previews are hidden from the chat list to reduce shoulder-surfing risks. SMART ACCESS & LOGIN • Fast phone-number login with OTP verification • Optional face-based sign-in on supported devices • Simple onboarding with name and phone number only • Ability to enable or disable biometric login at any time SECURE CHAT EXPERIENCE • Private chat list showing unread counts and privacy level, without message previews • Contact requests must be accepted before you can exchange messages • Per-message delivery and read indicators • Option to block users you no longer wish to receive messages from BUILT TO REDUCE DIGITAL TRACE OTRx-SDM is designed around the idea that sensitive conversations should be temporary: • Messages are temporary by default and disappear after the chosen timer • Screenshots, screen recording, screen sharing and screen mirroring are restricted inside the app • Tools to help users check whether they are in a more secure environment before messaging • Easy account and profile deletion from within the app JUST TEXT, NOTHING ELSE OTRx-SDM focuses on quiet, secure texting — no voice calls, video calls, photos, or file attachments. It is designed for users who care more about privacy and control than about broadcasting their lives. Learn more at https://otrx-sdm.com

ZIØN is a peer-to-peer, end-to-end encrypted messenger built on one principle: your conversations belong to you and your contact — no accounts, no cloud, no message database. HOW YOUR MESSAGES TRAVEL • On the same network, ZIØN connects your devices directly, device to device. Nothing leaves your local network. • Across different networks, messages are carried by a minimal relay we operate that only forwards already-encrypted bytes. It is zero-knowledge by design: it cannot read your messages, your contacts, or any content — and neither can we. • Optional WAN mode (OFF by default): when you enable it, ZIØN can also open a direct device-to-device connection across the internet via UDP hole punching. Only then does the app contact public IP-discovery services (ipify, ifconfig.me, icanhazip, checkip.amazonaws) to learn its own address for NAT traversal. There are no ZIØN accounts and no cloud storage of your messages. The relay never holds anything it can decrypt. STANDARD CRYPTO, ZERO CUSTOM • Curve25519 + ECDH key exchange • Forward Secrecy with per-session ephemeral keys • Authenticated AES-256-GCM message encryption • HMAC-SHA256 handshake authentication (anti-MITM) • 30-digit Signal-style safety numbers OPERATIONAL PRIVACY • Encrypted local storage • Excluded from iCloud backup • Self-destructing messages with configurable timer • Bidirectional message deletion • One-tap Emergency Wipe • Screenshot blocking, screen-recording detection • Session keys wiped from RAM on idle • Anonymous notifications: "New message" only, no sender or content LOCALIZED IN 6 LANGUAGES English, Italiano, Español, Français, Deutsch, 日本語 HONEST DISCLOSURE ZIØN is experimental software and has not undergone formal independent cryptographic audit. For communications where compromise would cause severe harm, use audited solutions like Signal. ZIØN is designed for users who want a second private channel between trusted devices. REQUIREMENTS iPhone 13 or later. iOS 17 or later. Face ID or Touch ID recommended.