Reconfiguration of FPGAs is becoming increasingly popular particularly in networking applications. In order to protect FPGA designs against attacks, secure reconfiguration must be performed. This paper introduces low cost solutions for protecting FPGA designs. This is achieved by implementing low cost hardware architectures of authenticated encryption (AES-CCM, AES-GCM, and PRESENT-GCM) in the static part of the FPGA to perform the decryption and the authentication of bitstreams. Presented architectures were evaluated by using 90 and 130 nm technologies.