Dead Drop 4+

Dead Drop is a secure, private and metadata-free messaging and calling platform.

After opening the app, your device will generate a unique set of cryptographic keys that is used to securely communicate with others.

To communicate, you will need to meet up with another user in person and verify each other's identity, and then scan each other's code to exchange public keys and add one another to your respective contact lists.

Note that for privacy and security reasons, you can only receive messages or calls from users that are registed in your contacts list. As such, if you are not in possession of a public key for a particular user, you cannot receive their messages or call requests, thus eliminating unknown SPAM and mailicious messages.

There is no user search function on the platform, users instead form their own private closed contact groups by exchanging keys in person.

Cryptography details:
- The app uses X25519 and Ed25519 keys for your own identity.
- Authenticated HPKE is used to generate a unique symmetric key every time you send a message via X25519 with SHA256 as an encapsulation mechanism and SHA384 for key derivation.
- Messages and calls are end-to-end encrypted using the ChaCha20-Poly1305 AEAD cipher.