This thesis describes implementation of an Advanced Encryption Standard (AES) Smart Card, a highly tamper resistant to Side Channel Attacks. Smart Cards are gaining popularity in applications that require high security and store sensitive information. Modern smart Cards, highly capable of complicated cryptography, provide a high assurance of tamper resistance and thus commonly used in payment application. However, advanced Smart Cards can not protect attackers from being defrauded by different side channel attacks (DSCA). Small, embedded integrated circuits (ICs) such as smart cards are vulnerable to side channel Attacks (SCAs) The development of such attacks describes how to perform different kinds of side channel Attack on an AES implementation by using simulated power traces. Working in a simulated environment brings relevant advantages,e.g., eventual weakness to Differential power Attack(DPA) may be detected at device designing phase,so that satisfactory countermeasures can be adopted before the physical realization. The security prevention from such corresponding attacks is a randomized masking technique for implementing in software and hardware,which has been discussed here