Smart cards were born as a secure and powerfully built device. The main feature smart cards introduce is that they process data in a safe way because they support the implementation of cryptographic algorithms based on keys. A cryptographic key is a set of information that controls the operation of a cryptographic algorithm. In the context of the project a cryptographic key is used to verify if somebody has the authorisation to access a service or a system. Nowadays there are two different methods of encrypting a message: the symmetric key algorithms, which use the same key to encrypt and decrypt, and the asymmetric key algorithms, which use two cryptographic keys and allow anyone to encrypt using the public key while only the owner of the private key can decrypt the message. In the opposite way as it was first thought, several attacks have appeared and have made smart cards vulnerable. For this reason, manufacturers are investing a lot of money investigating and implementing countermeasures in order to improve the security of these devices. Countermeasures are used to protect these keys from potential threads. One of the attacks used to break the security of smart cards is the Electromagnetic Analysis Attack, also called EMA. The EMA attack is a concrete attack of the family of Side-Channel Attacks which are based on extracting information without leaving signals in the card. This attack is based on capturing electromagnetic waves generated by the chip with an antenna while cryptographic processes are being performed. At this point, the data obtained are processed in such a way that the secret key of the cryptographic algorithm could be broken. At this stage, the project is split into two main parts. In the first part, theoretical concepts will be introduced in order to understand how the attack works and give a brief concept about the state of art. On the other hand, in the second part of the thesis a real attack will be performed. The subject of the attack will be a smart card with cryptographic operations implemented. The objective is to extract the secret key. This project has been developed in Applus, in the Chip department. Applus is a certificatory company. The Chip department staff are experts in smart card security and they are investigating new attack methods continuously.