A system and method are described supporting secure implementations of 3DES and other strong cryptographic algorithms. In one implementation, the speech-VBD discriminating apparatus calculates both short-term delay and long-term delay SSR values to analyze the repetition rate of an input signal frame, thereby indicating whether the input signal frame has the periodicity characteristics of a typical speech signal or a VBD signal. The partitioning member has an engagement part to be engaged with the top edge of the upstanding wall from the front side and a fixing part closely contacting the bottom surface of the front part of the partition wall continuing to the upstanding wall when the engagement part is engaged with the top edge of the upstanding wall.