A multi-electrode catheter has a longitudinally extending body with a number of longitudinally extending lumens formed therein and a number of electrode assemblies. Then, a 9-bit round key KIij1 is truncate-converted to seven bits, the exclusive OR of the seven bits and the round key KIij1 is calculated by an exclusive OR and the calculation result is inputted to an exclusive OR arranged on the right system data path in the second stage MISTY structure. Methods of treating bacterial infections using the compositions containing the bacteriophages in combination with conventional antibiotics also are disclosed.