Protect a secret by splitting it in multiples shares and send them to all your devices or to your trusted peers.

You can send shares of a secret to all your devices (iPhone, iPad, iPod touch) or to trusted peers also running Core Secret. To later access a secret a peer will need to collect the other existing shares in order to recover the secret.

Shares of a secret are shared between devices through Bluetooth Low Energy (also known as Bluetooth 4.0). Thus peers must be at proximity in order to be able to share or recover a secret. It is currently possible to encrypt and share a secret note, a small file (limited to 100kB), a contact, a password or an encryption key.

Additionally an encryption key can be used to encrypt larger files or photos and small videos and share these encrypted items with your peers through Airdrop, by Mail or via a QR code (if the encrypted data is really small).

On the technical side, Shamir's threshold secret sharing is used to generate secret shares, NaCl primitives (Curve25519, Salsa20, Poly1305) are used for encryptions. Read the online documentation at coresecret.io for more details on its cryptographic mechanisms.

Note that this application requires Bluetooth 4.0. Also, although Airdrop is not mandatory, functionalities relying on Airdrop will be unavailable if it is missing.