What end-to-end encryption means in Umbera
End-to-end encryption means the message is locked on the sender’s phone and unlocked only on the recipient’s phone. Nobody in between — not the network, not the relay, not the Umbera server — has the keys to read it.
Umbera uses a Double Ratchet session, so the keys change with every message. If one key ever leaked, it would not unlock past or future messages.
Post-quantum encryption: X25519 + ML-KEM-1024
A large enough quantum computer could break today’s widely used key exchange, and encrypted traffic recorded now could be decrypted later. To protect against this, each Umbera envelope is sealed with two algorithms at once: the classic X25519 and ML-KEM-1024 (Kyber), the post-quantum standard selected by NIST.
To read a message an attacker would have to break both. Keys are derived with HKDF-SHA256 and the content is encrypted with AES-256-GCM.
Encrypted group chats
Group keys are agreed using MLS (RFC 9420), the IETF standard for secure group messaging. The server does not know that a conversation is a group or who its members are.
Encrypted files, photos, videos and voice notes
Attachments are encrypted on the sender’s device, with a separate key for each file. Metadata is removed from PDF files before they are sent.
Encrypted voice and video calls
Calls are encrypted with DTLS-SRTP directly between the devices, and the keys never leave the phones. When a direct connection is not possible, a relay forwards the packets, but it only sees ciphertext and has no keys.
Don’t trust us. Verify.
Claims about encryption are easy to make, so Umbera publishes the cryptographic core as open source along with tests anyone can run: a message cannot be opened with another key, breaking X25519 alone is not enough, and tampered messages are rejected. The proof page walks through every step, including a traffic check in Wireshark.
Frequently asked questions
Is Umbera end-to-end encrypted?
Yes. Messages, files, voice notes and calls are encrypted on your device, and only the recipient can decrypt them. End-to-end encryption is always on and cannot be turned off.
What encryption does Umbera use?
Double Ratchet sessions, with each envelope sealed by X25519 + ML-KEM-1024 (Kyber), keys derived with HKDF-SHA256 and content encrypted with AES-256-GCM. Groups use MLS (RFC 9420), calls use DTLS-SRTP.
Is Umbera quantum-safe?
Messages are sealed with a hybrid of X25519 and the post-quantum ML-KEM-1024, so an attacker would need to break both, including with a quantum computer.
Can Umbera read my messages?
No. The server only receives ciphertext and a mailbox address. It does not have the keys and does not know who sent the message.
Is the code open source?
The cryptographic core and the tests that check it are public on GitHub, so anyone can verify how messages are encrypted.
Try Umbera
Available on Android and iPhone. The trial is free and starts on first launch — no card required. See exactly what the server can and cannot see on the proof page.