Several grouping proof protocols were presented to meet the security requirements of Radio Frequency Identification Systems. Nevertheless, these protocols were shown to be vulnerable to various attacks. In this work, we cryptanalyze one of the newest grouping proof protocols. Through this analysis, we show the weaknesses of the protocol and launch a full-disclosure attack to disclose all secrets in the protocol. We show that the probability of success of the protocol is one and that increasing the length of the strings adds little complexity to the attack. We follow this by proposing an enhanced version of the protocol with better overall security. We show its efficiency by providing a security and performance analysis and comparing it with some of the existing protocols in the literature.