NIP-55 (Native App) Signer

The Nip55Signer implements the ISigner interface by communicating with native mobile signing applications through the Capacitor plugin system. This implementation is particularly useful for mobile applications that want to leverage native Nostr signing capabilities.

Prerequisites

The signer requires the Capacitor plugin to be installed:

npm install nostr-signer-capacitor-plugin

@welshman/signer does not import the plugin itself — it only describes the shape it needs as the Nip55 type, so that apps which don't support NIP-55 never have to resolve a package they haven't installed. Your app hands the plugin over once at startup:

import { NostrSignerPlugin } from 'nostr-signer-capacitor-plugin'
import { setNip55Plugin } from '@welshman/signer'

setNip55Plugin(NostrSignerPlugin)

Until you do, getNip55() returns an empty list and Nip55Signer operations reject with "Nip55 is not enabled" — the same way Nip07Signer behaves without a browser extension.

Getting Started

import { Nip55Signer, getNip55 } from '@welshman/signer'

// Check for available signing apps
const apps = await getNip55()
if (apps.length > 0) {
  const optionalSavedPubkey = localStorage.getItem('my-saved-pubkey')
  const signer = new Nip55Signer(apps[0].packageName, optionalSavedPubkey)
}

API Reference

Registering the Plugin

setNip55Plugin(plugin: Nip55 | undefined): void
getNip55Plugin(): Nip55 | undefined

Detecting Available Signers

// Returns information about installed signing apps, or [] if no plugin is registered
getNip55(): Promise<Nip55AppInfo[]>

interface Nip55AppInfo {
  name: string
  packageName: string
  iconUrl?: string
}

Constructor

constructor(packageName: string, publicKey?: string)

Creates a new signer instance that will communicate with the specified native app.

• packageName: The package identifier of the native signing app
• publicKey: optional user pubkey. Recommended for resuming existing signer sessions when the signer is managing multiple user accounts.

Complete Example

import { NostrSignerPlugin } from 'nostr-signer-capacitor-plugin'
import { Nip55Signer, getNip55, setNip55Plugin } from '@welshman/signer'
import { makeEvent, NOTE } from '@welshman/util'

setNip55Plugin(NostrSignerPlugin)

async function example() {
  try {
    // Get available signing apps
    const apps = await getNip55()
    if (apps.length === 0) {
      throw new Error('No native signing apps available')
    }

    // Create signer with first available app
    const signer = new Nip55Signer(apps[0].packageName)

    // Get public key
    const pubkey = await signer.getPubkey()
    console.log('Public key:', pubkey)

    // Sign an event
    const event = makeEvent(NOTE, {
      content: "Hello from native app!",
      tags: [["t", "test"]]
    })
    const signedEvent = await signer.sign(event)
    console.log('Signed event:', signedEvent)

    // Encrypt a message
    const encrypted = await signer.nip44.encrypt(
      recipientPubkey,
      "Secret message"
    )
    console.log('Encrypted:', encrypted)

  } catch (error) {
    console.error('Native signer error:', error)
  }
}