1. A microelectronic apparatus for generating random binary words comprising: at least one clocked pseudorandom binary number sequence generator normally operative to generate a cyclic output sequence of binary numbers, each number comprising a string of binary symbols, the cyclic output sequence comprising a basic sequence which is generated repeatedly; at least one bit stream generator generating a clocked bit stream including a stream of binary symbols of a first type occasionally interrupted by a binary symbol of a second type, wherein a first varying time interval between the occasional interruptions is intractably correlated to the output sequence of said number sequence generator, wherein each occurrence of an interruption of the stream of binary symbols of the first type by a binary symbol of the second type causes a pseudorandom modification of the cyclic output sequence of said number sequence generator; and a sampling device operative to sample said cyclic output sequence of binary numbers thereby to generate a sampled output sequence comprising at least one sampled binary word.