Si4iMsg

Si4iMsg turns an iMessage into a capsule. When your friend taps it, the message opens with a reveal effect: fireworks, a thunderstorm, falling cherry blossoms, a stomping T. rex, or the animal of the Chinese zodiac with a New Year greeting. Turn on end-to-end encryption, and only your devices and your friend's can read it. Everything happens in Messages. There is no account and no sign-up. REVEAL EFFECTS • Basic: fireworks, lightning, scratch card, typewriter and flip card • Weather: wind, rain, thunderstorm, snow, fog, sunshine, rainbow, sandstorm, typhoon and aurora • Plants: cherry blossom, rose, sunflower, bamboo, maple leaves, dandelion, tree and four-leaf clover • Dinosaurs: T. rex, brachiosaurus, pterosaur, raptors, a dinosaur egg, a volcano, a fossil to brush free, a fire dragon and a water dragon • Chinese zodiac: all twelve animals, each with its own entrance, plus a greeting you pick or write yourself Effects play on your friend's device and follow Reduce Motion and VoiceOver. END-TO-END ENCRYPTION, WHEN YOU WANT IT • Off at first, so you can start right away. Turn it on for a conversation with one tap. • You and your friend swap public keys once, inside the conversation. • Each device has its own private key, made in its Secure Enclave. It never leaves the device and is never backed up. • Every message is encrypted on your device for each of your friend's devices and each of yours (HPKE with P-256, AES-GCM). • Compare a key code in person or on a call to be sure you have the right key. READ-ONCE AND EXPIRING CAPSULES • A read-once capsule opens once, then it is gone. • Capsules can expire after a time you choose. HOW CAPSULES TRAVEL Si4iMsg uploads each capsule to a relay server and sends a short link as the iMessage bubble. For an encrypted capsule the relay only ever gets ciphertext. You can add your own relay, or choose "No relay" to carry a short capsule inside the link itself. Capsules without encryption, and every capsule in a group chat, reach the relay as plain text. The readable copies stay on your devices. GOOD TO KNOW • Your friend needs Si4iMsg to open capsules and see the effects. • Group conversations send capsules without encryption. • In English, Simplified Chinese, Japanese, German, Korean, Spanish and French. No ads. No tracking.