The use of lightweight and light weight block ciphers in the Internet of Things is inevitable. Recently, Midori64 has received a lot of attention among other lightweight ciphers due to its very low power consumption. Midori64 security has been threatened by various attacks, including side channel attacks. One of the types of side channel attacks is correlation power analysis, in which an attacker can discover the encryption key by using the power leak of the cryptographic chip while the algorithm is running, data being processed and operations being executed. Masking against power analysis attacks is known as one of the most effective methods of cryptographic algorithms. The purpose of the mask is to disrupt the relationship between power consumption and ongoing operations. In this paper, an implemented version of the Midori64 code on an Atmega32 AVR micro-controller is attacked by correlation power analysis, and an encryption key with 300 blocks of plain text is discovered. After masking the Midori64 with the Boolean masking method, the attack was performed again, and the experimental results showed that the Boolean masking method could prevent key discovery.