Side channel analysis is a non-invasive cryptanalysis attack categorized as an implementation attack. Electronic device leak information during the data processing via covert side channels. Power consumption, electromagnetic (EM) radiations, and process timing information are various side channels that can be exploited to steal the secret information. An EM side channel is a non invasive side channel. With the help of statistical analysis methods, the EM emanation captured from the cryptographic device reveals the secret encryption key. Non invasive side channel attacks are difficult to detect and thus it is necessary to design cryptographic engine/ secure engine resilient against side channel attacks. This thesis demonstrates the EM side channel attack and discusses the state of the art countermeasures against the EM side channel. The attack is demonstrated on the 128-bit Advanced Encryption Standard (AES)\cite{fouteen} encryption that can reveal the secret key and explores the the countermeasure for making the crypto engine resistant against the side channel attack using the key update scheme. The other technique include hiding and masking countermeasures.