A catheter system for injecting therapeutic agents including large molecules into the body. The method includes associating a random number generator in the security element with a portion of a non-volatile memory in the security element, and activating the RNG to automatically write, during a normal operation mode of the security element, a new random number into the portion of the NVM whenever an attempt is made to write into the portion of the NVM. A base connection of the NPN bipolar junction transistor is described as coupled to a body of the n-channel access transistor.