The main goal of this chapter is to study FPGA devices in the field of secured applications. We mainly address data protection based on a well defined threat model. When dealing with FPGAs at the system level, two kinds of data are of paramount importance: bitstream and external memory. To cover these topics, we first review state of the art FPGA security mechanisms and good practices, followed by performance analysis achievable using hardware implementation of cryptographic algorithms in current FPGAs. We then tackle external memory protection and how FPGAs can provide an efficient solution. Next, we highlight security issues specific to FPGAs, bitstream replay attacks, for example, and suggest solutions to improve bitstream management security, focusing on secure remote updating of FPGA bitstreams. Finally we give the results of a concrete case, i.e., a platform based on an FPGA device. This last section provides both a practical and an industrial point of view that will enable readers to evaluate the pertinence of the solutions proposed.