Electronic voting (e-voting) systems have been inuse since the 1960s. E-voting offers many advantages compared to other voting techniques. However, it also introduces many security challenges. As it may contain malicious back-doors that can affect system dependability. In this work, we present one of e-voting challenges where the hardware Trojan tampers results totally. We implement an e-voting machine as a case study on XilinxFPGA board. Then, we inject a hardware Trojan to tamper voting results. The attack depends mainly on the unused bits. We provide a protection technique and show its overhead. Furthermore, we introduce other attacks and protection scenarios. We compare between our selected protection techniques and others techniques. Finally, we illustrate that our chosen protection technique incurs negligible power overhead, whereas the average area and delay overheads are 4% and 10%, respectively.