Many cryptography algorithm contain a lots of data bit manipulation operations. Unfortunately, the Instruction Set Architecure (ISA) of general purpose microprocessors is usually word oriented. Consequently the execution of this kind of algorithms is not optimized and the computation of data represented by single bits or sub-words can require several clock cycles. Reconfigurable hardware accelerators oriented to the bit manipulation could accelerate the computation of these algorithms increasing the microprocessor performance in terms of execution time. This work presents the experimental results of the speed-up factor obtained for the implementation of TDES (Triple Data Encryption Standard) algorithm when a Reconfigurable Functional Unit ADAPTO [1] is integrated with a RISC microprocessor (the Altera NIOS-II soft processor [2]). The ADAPTO unit, described in VHDL (VHSIC Hardware Description Language), has been implemented on an Altera-Stratix II FPGA and integrated with the Nios soft processor using the Custom Logic feature [4]. The objective is the measurement of the speed-up factor related to the introduction of the reconfigurable hardware accelerator.