AmberNostr Event Signer for Android and Windows

What Amber Is and Why Nostr Users Need a Signer

Nostr is a decentralized protocol where you publish signed messages, called events, through independent relays. Every event you post is signed with a private key, which Nostr users usually store as an nsec, while the matching public key, an npub, is what others use to find you. Anyone holding your nsec can publish as you, which is why the key is the most sensitive piece of a Nostr identity.

Many people end up pasting their nsec into several clients, browser tools and bots. Each copy is another place the key can leak, whether through a compromised app, a careless backup or a malicious update. Amber is built to reduce that spread. It acts as a dedicated signer: your key stays in Amber, and other apps only receive the finished signatures they need.

The project's design rationale is that private keys should be exposed to as few systems as possible, since each system adds to the attack surface. That principle, more than any single feature, explains why Amber exists.

How Remote Signing Works Through NIP-46

Remote signing means the app that needs a signature and the device that holds the key are separate. Under NIP-46, a client app sends a request to sign an event, and the signer returns the signed result. Amber takes the signer role, so the client never needs the nsec itself.

In practice, the flow looks like this. You open a Nostr app that supports remote signing, it asks for a connection, and you approve the link in Amber. When the app wants to publish a note, it sends the event to Amber, which displays it for your review before anything is signed. You decide whether to allow it, and only the signature goes back.

Because the signing step is isolated, a compromised client cannot quietly read your key. It can still request signatures, so reviewing requests carefully matters. The remember my choice option is useful for apps you trust, but it also means fewer prompts, so use it deliberately.

Who Amber Is For: Practical Scenarios

Amber suits people who already use several Nostr apps and want one place to manage signing. A user who posts from a phone client, a desktop client and a web tool, for example, would otherwise need the same key in three locations. With a signer, the key stays put and each tool only asks for signatures.

Developers testing Nostr applications are another group. A test app can request signatures from a separate signer while you keep your everyday key out of experimental code. That separation also makes it easier to stop one app from signing on your behalf without changing your identity.

Privacy-minded users who want to limit key exposure will also find the design appealing. Amber is not a full social client, so it does not replace the apps where you read and write posts. It fills the narrower role of holding keys and approving signatures. People who want a single, all-in-one app may find it too narrow for their needs.

Supported coins

Amber works with the Nostr protocol. It signs Nostr events rather than moving cryptocurrency, and the project's documentation lists Nostr as its supported network. Connections to client apps rely on NIP-46, so any Nostr client that supports that approach can request signatures through Amber. Amber does not manage coin wallets or blockchain networks.