A lot of devices which are daily used (i.e., credit card, pay-tv card, e-passport) have to guarantee the retention of sensible data. Sensible data are ciphered by a secure key by which only the key holder can get the data. For this reason, to protect the cipher key against possible attacks becomes a main issue. Many research activities have been directed in developing countermeasures to enhance the device resistance against attacks and, on the other side, many contributions aimed to enhance the attack itself have been reported in the technical literature. This book is a collection of the main results of a PhD in hardware cryptography about side-channel attacks and countermeasures in the design of secure IC’s devices. About hardware countermeasures against power analysis, three new logic families for cryptographic applications are designed. With respect to the contributions aimed to enhance the attack methodologies, an active circuit which promises to improve the power attacks is proposed. Besides, a new side channel and a novel methodology to attack cryptographic circuits is studied. Finally, two activities focused on Random Numbers Generators are briefly described.