Keep for AndroidSplit Your Nostr Keys Across Devices

What Is Threshold Signing and Why Does It Matter?

A normal Nostr identity is controlled by a single private key. Whoever holds that key can sign anything as you, and if the key is lost, the identity is gone. Threshold signing changes the model. The key is split into several shares, and a signature is produced only when enough of those shares cooperate.

With FROST, the shares never recombine into a full private key during signing. Each share holder contributes a partial signature, and the partials are merged into one ordinary Schnorr signature that looks the same as any other signature to the outside world.

For a Nostr user, this means that compromising one phone does not automatically expose the identity. An attacker would need to reach a quorum of shares, which is a meaningfully higher bar than stealing a single nsec string.

Who Is Keep for Android For?

Keep suits people who already use Nostr seriously and want stronger control over their keys than a single stored nsec provides. Typical users include individuals who post under a public identity they cannot afford to lose, small teams that want shared control over a brand account, and developers testing signing flows.

It is less suited to someone who only browses Nostr casually. Setting up shares, deciding on a threshold and keeping backups of share material all take planning. If you are new to Nostr itself, it is worth learning how keys and relays work before adding a threshold layer.

Because Keep also handles existing nsec keys, it can serve as a single-device signer during a transition, with the option to move toward a multi-device setup later.

How Remote Signing Changes the Client Experience

Most Nostr clients were built to hold keys themselves. Keep changes that relationship. With NIP-55, an Android client sends a signing request to Keep through the system, and Keep shows the request for approval. The client never sees the key.

NIP-46 extends the idea to other machines. A desktop or web client can connect to Keep as a remote bunker, so signing happens on your phone while the interface runs elsewhere. Requests still pass through your approval rules, so nothing is signed silently just because a client asked.

The practical benefit is that you can use the clients you like while keeping the key in one controlled place.

Key Concepts Behind FROST and Share Management

Several terms come up repeatedly when working with Keep. A threshold, written as M-of-N, is the number of shares needed out of the total. A 2-of-3 setup can sign with any two of three shares, so losing one share does not lock you out, but any two shares together are enough to sign, so they should be kept apart.

Share distribution is the most important decision. Spreading shares across a phone, a second device and a secure backup reduces the chance that one event wipes out access. Concentrating all shares on one device defeats the purpose.

A signing policy is a rule attached to an app or account, for example limiting which event kinds it may request. Reviewing these rules periodically is a good habit, especially after installing a new client.

Supported coins

Keep's documentation refers to Bitcoin (BTC) and the Nostr network. Its signing role is centered on Nostr identities, and the FROST key-handling is the feature that sets it apart from ordinary Nostr signers.