title: Firebase ID token has invalid signature even on jwt
body: <p><strong>Firebase ID token has invalid signature</strong></p>
  <p>Hi all, I'm somehow new to NodeJS and I've only used Google Firebase a few times.
  Now, I'm trying to verify an idToken generated using <code>getIdToken()</code> method whenever a user signs up or signs in. The token generation works fine but if I try to use this token to authorize a user <code>admin.auth().verifyIdToken(idToken)</code> on another route, I get this error <strong>Firebase ID token has invalid signature</strong> on Postman. I tried to verify the token on jwt.io as well, it gave error <strong>Invalid Signature</strong>.</p>
  <p>I tried switching to different algorithms, some eventually made the token valid on jwt, but there is usually a VERIFY SIGNATURE box by the bottom-right which I don't really know what to fill there. Well, I've tried copying different newly generated valid tokens by jwt after changing algorithm, but I still get <strong>Firebase ID token has invalid signature</strong> from Postman.</p>
  <p>Does anyone know what the problem may be? Please help.</p>