A key variable loader receives a set of Rijndael parameters that were verified using a simulation computer, wherein the set of Rijndael parameters provide an input for implementing at least one step of the Rijndael block cipher and when used with a secret key allow a conversion between plain text and cipher text using the Rijndael block cipher. The key variable loader further stores the set of Rijndael parameters and subsequently provides the set of Rijndael parameters to a device having a customizable Rijndael block cipher, like a subscriber unit or a key management facility.