ZeroHawk

Named for what it does

Zeroize is the standard term in defence cryptography for destroying key material.

Expiry here does not delete your data. It destroys the key that reads it, and deliberately keeps the ciphertext — so the guarantee can be demonstrated rather than asserted. The bytes are still on the server, and nobody can read them.

Deleting data is a policy promise: it fails the moment one server quietly keeps a copy, and in this threat model that server is the adversary. Destroying the key is a mathematical promise — it holds even against the machine that cheated.

What it guarantees — and what it does not

Every guarantee is paired with its limit. The common failure in secure communications is not weak cryptography but a claim that outruns it.

• The server cannot read your messages — Not by policy — it holds no private key. It still sees who corresponds with whom, and that metadata is not protected.
• After expiry nobody can read it — Including the operator. But a recipient who opened it beforehand may have kept what they read — a screenshot, a photograph. That limit is shared with Signal and Snapchat.
• Tampering is detectable by someone other than the operator — An append-only hash chain, anchored externally. Detectable, not impossible.
• Keys can live in hardware that will not surrender them — A Secure Enclave key can be used to decrypt and cannot be copied out. It still does not survive a compromised device.

Independently checkable

Nothing here asks to be taken on trust.

The implementation ships with suites an evaluator runs themselves: the cryptographic guarantees, interoperability between two independent implementations, hardware custody against real silicon, and an adversary holding root on the node — which reports its own outstanding finding rather than only its successes.

Read the technical whitepaper