  By expanding the connection of objects to the Internet and their entry to
human life, the issue of security and privacy has become important. In order to
enhance security and privacy on the Internet, many security protocols have been
developed. Unfortunately, the security analyzes that have been carried out on
these protocols show that they are vulnerable to one or few attacks, which
eliminates the use of these protocols. Therefore, the need for a security
protocol on the Internet of Things (IoT) has not yet been resolved.
  Recently, Khor and Sidorov cryptanalyzed the Wang et al. protocol and
presented an improved version of it. In this paper, at first, we show that this
protocol also does not have sufficient security and so it is not recommended to
be used in any application. More precisely, we present a full secret disclosure
attack against this protocol, which extracted the whole secrets of the protocol
by two communication with the target tag.
  In addition, Sidorv et al. recently proposed an ultralightweight mutual
authentication RFID protocol for blockchain enabled supply chains, supported by
formal and informal security proofs. However, we present a full secret
disclosure attack against this protocol as well.
