code: func (c *Client) checkMatchingKeys() {
  	serverKey, err := c.ServerKeyID()
  	// The server provides the full (16 digit) key fingerprint but schema.Signer only stores
  	// the short (8 digit) key ID.
  	if err == nil && len(serverKey) >= 8 {
  		shortServerKey := serverKey[len(serverKey)-8:]
  		if shortServerKey != c.signer.KeyID() {
  			log.Printf("Warning: client (%s) and server (%s) keys differ.", c.signer.KeyID(), shortServerKey)
  		}
  	}
  }
docs: // checkMatchingKeys compares the client's and the server's keys and logs if they differ.