basic functionality, untested.

extension/background.js

@@ -1,9 +1,34 @@
-browser.runtime.onMessage.addListener((req, sender, reply) => {
-  switch (req.type) {
-    case 'getPublicKey':
-      reply({})
-      break
-    case 'signEvent':
-      break
+import browser from 'webextension-polyfill'
+import {validateEvent, signEvent, getPublicKey} from 'nostr-tools'
+
+browser.runtime.onMessage.addListener(async (req, sender, reply) => {
+  let {type, params, host} = req
+
+  try {
+    switch (type) {
+      case 'getPublicKey': {
+        let results = browser.storage.local.get('private_key')
+        if (results && results.private_key) {
+          reply(getPublicKey(results.private_key))
+        } else {
+          reply({error: 'no private key found'})
+        }
+        break
+      }
+      case 'signEvent': {
+        let {event} = params
+        if (!validateEvent(event)) return reply({error: 'invalid event'})
+
+        let results = browser.storage.local.get('private_key')
+        if (results && results.private_key) {
+          reply(signEvent(event, results.private_key))
+        } else {
+          reply({error: 'no private key found'})
+        }
+        break
+      }
+    }
+  } catch (error) {
+    reply({error})
   }
 })