The present invention relates to an apparatus and method for secure information processing. In one example embodiment, a circuit arrangement includes a universal asynchronous receivertransmitter chip having a FIFO circuit and an arithmetic logic unit adapted to generate an N-bit variable binary signal, wherein the binary signal varies as a function of a current storage capacity of the FIFO circuit. The charge pumping circuit may be employed in a direct current converting circuit so that it is insensitive to the threshold voltage of a transistor. To compensate for stop words, a weight function is applied to a predetermined component of the document vectors associated with frequently occurring word contained in the documents.