In today's information society, cryptography has become one of the main tools for privacy, trust, access control, electronic payments, corporate security, and countless other fields.The most important objective of cryptography is represented, without a doubt, by achieving confidentiality. In the last years there has been intense research on a new source of information security: chaotic functions. Our project tries to make a step forward in the field of chaotic based cryptography for data confidentiality. We will present three different encryption algorithms. The first two are block ciphers. They are explained in detail, and we discuss the original versions of the algorithms, their weaknesses and the proposed improvements. For the first algorithm the proposed improvement targets the speed, while for the second one the proposed improvement the security. For the third algorithm that is studied in this project we present its characteristics and we study its implementation on FPGAs using VHDL.