This paper presents practical results on the evaluation of fault countermeasures implemented in an asynchronous DES coprocessor. The theory underlying the countermeasures was previously published in IOLTS 2005. For the first time this work reports a practical evaluation of fault countermeasures applied on asynchronous DES ASICs. Two DES crypto processors were fabricated using the 130 nm STmicroelectronics CMOS process; one as a reference and one hardened using a specific technique. This work enables us to compare the resistance of both circuits against fault injection and to validate the proposed countermeasures. The practical set-up of the fault injection, using a laser, is presented and the test campaign described. The practical results prove the efficiency of the method. The techniques can be applied to protect logic blocks in any applications.