Generate key on startup or load from keystore.

lib/main.dart

@@ -1,5 +1,4 @@
 import 'dart:convert';
-import 'dart:io';
 
 import 'package:dartssh2/dartssh2.dart';
 import 'package:flutter/material.dart';
@@ -67,7 +66,6 @@ class _MyHomePageState extends State<MyHomePage> {
   OpenSSHEd25519KeyPair? keyPair;
   String _output = '';
   String key = '';
-
   Future<void> doSSH() async {
     SSHSocket? socket;
 
@@ -96,14 +94,36 @@ class _MyHomePageState extends State<MyHomePage> {
     }
   }
 
-  Future<void> generateKey() async {
+  Future<void> obtainKeyPair({bool regenerate = false}) async {
     // Generate a key pair
 
+    final storage = const FlutterSecureStorage();
+    final storedKey = await storage.read(key: 'ssh_key_pair');
+
+    // Restore the key if we have one stored and regeneration is not requested
+    if (storedKey != null && !regenerate) {
+      // If we have a stored key, use it
+      final keyPairsFromStorage = SSHKeyPair.fromPem(storedKey);
+      assert(keyPairsFromStorage.length == 1);
+      assert(keyPairsFromStorage[0] is OpenSSHEd25519KeyPair);
+
+      final keyPairFromStorage =
+          keyPairsFromStorage[0] as OpenSSHEd25519KeyPair;
+
+      setState(() {
+        keyPair = keyPairFromStorage;
+        key = encodePublicKey(keyPairFromStorage, comment: "leinelab-app-key");
+      });
+      return;
+    }
+
     final generatedKeyPair =
         await generateKeyPair(); // local variable avoids downcast to ? ptr
-    keyPair = generatedKeyPair;
+
+    await storage.write(key: 'ssh_key_pair', value: generatedKeyPair.toPem());
 
     setState(() {
+      keyPair = generatedKeyPair;
       key = encodePublicKey(generatedKeyPair, comment: "leinelab-app-key");
     });
 
@@ -113,6 +133,14 @@ class _MyHomePageState extends State<MyHomePage> {
     );
   }
 
+  @override
+  void initState() {
+    super.initState();
+
+    // we do not await generateKey() here, as this is the intended way
+    obtainKeyPair();
+  }
+
   @override
   Widget build(BuildContext context) {
     final String outputText = _output.isNotEmpty
@@ -143,7 +171,7 @@ class _MyHomePageState extends State<MyHomePage> {
     );
 
     final actionButtonInfo = FloatingActionButton(
-      onPressed: generateKey,
+      onPressed: () => obtainKeyPair(regenerate: true),
       tooltip: 'Regenerate Key',
       child: const Icon(Icons.refresh),
     );