Long Term Evolution (LTE) is the standard for high-speed wireless communication for mobile devices and data terminals. Although, the 3rd Generation Partnership Project (3GPP) has specified some security mechanisms to insure the security of intra-MME handover, but there exists a few vulnerabilities compromising the security of the LTE entities. The most harmful vulnerability is the de-synchronization attack. This attack aims to compromise the new session keys using a false base station by desynchronizing the target eNodeB during the handover process. In this paper, a modification for the standard protocol is presented to overcome this attack. Also the paper investigates the performance of the modified protocol in terms of the handover phase's latencies according to the 3GPP technical specifications. Finally, the opensource framework LTE-Sim is used to provide complete performance evaluation for the modified protocol, by measuring the received packets average delays and the Packet Error Loss Ratio (PELR) of the transmitted packets, comparing with the 3GPP requirements.