Allow to choose if extractable or not

src/private-wrap.ts

@@ -17,11 +17,11 @@ export class PrivateWrap {
         private readonly pubkey: CryptoKey,
     ) {}
 
-    public static gen_keypair() : Promise<CryptoKeyPair> {
+    public static gen_keypair(extractable : boolean = true) : Promise<CryptoKeyPair> {
         log.trace("generate keypair")
         return crypto.subtle.generateKey(
             algorithm,
-            true,
+            extractable,
             ["deriveKey"],
         )
     }