Security

How Hushpiper protects what you send, what isn't finished yet, and how to tell us about a problem.

Your messages are locked on your device

When you install Hushpiper, your device makes its own key pair. The private key never leaves the device. When you send something:

Your device locks the message with a brand-new key (AES-256-GCM).
It seals that key separately for every device in the chat, using each device's public key (X25519 with HKDF-SHA256).
Our server receives a sealed envelope it can't open, hands it to each device, and deletes it once every device has it. Photos and files are deleted after 7 days at the latest.

This covers text, photos, videos, voice notes, files, stickers, locations, polls, reactions, statuses and call set-up. Encrypted backups are a file you keep, locked with a password only you know.

Calls

One-to-one and small group calls go directly between phones where possible, encrypted by the standard WebRTC protocols (DTLS-SRTP). When a call needs our relay or our media server, the relay passes encrypted audio and video it can't decode, and group calls on the media server add a second layer of end-to-end encryption with a key only the people on the call have.

What isn't finished yet

We'd rather tell you than have you find out:

No forward secrecy yet. Each device uses one long-term key. If someone stole a device's key and had also recorded that device's encrypted traffic, they could open those old messages. We are moving to MLS (Messaging Layer Security, RFC 9420), the new standard that fixes this with keys that keep changing.
One key across chats. Your device's public key is the same in every chat, so our server could tell that two "anonymous" group members are the same device. MLS will give each chat its own key.
Independent review. Our own review is done; an outside security audit will follow before we leave beta.

On your device

App lock with a PIN or your fingerprint or face.
Hidden chats in a vault behind a second PIN.
A wipe code: typed instead of your password, it signs out and erases every device.
Chats can block screenshots, saving and forwarding (on devices that allow it).

On our servers

All connections use HTTPS (TLS). We never log message contents, because we never have them.
Sign-in and sign-up are rate limited, and a lost password is reset only with your 12-word recovery phrase.
To stop banned people coming back, we keep one-way scrambled (HMAC) versions of network addresses and app install IDs for 30 days, not the addresses themselves.
Files have no public web address: every download checks that you're in the chat.

Report a security problem

If you think you've found a vulnerability, email security@hushpiper.com with what you found and how to reproduce it. Please don't include other people's data, and give us a reasonable time to fix it before telling anyone else.

We'll reply within 5 working days and keep you updated.
We won't take legal action against research done in good faith that respects our users' privacy and stays within these rules.
We don't have a paid bug bounty yet, but we'll gladly credit you.

Machine-readable contact details: security.txt.