A pseudo random generator comprising a shift register comprising a first flip flop (F0) and n further flip-flops (F1 . . . Fn) each flip-flop (F0) having a D input, a non-inverting output, an inverting output, and a common clock (fclk) input and the first flip-flop (F0) having a set input, each of the non-inverting outputs being connected via a NOR gate (10) to the set input of the first flip-flop (F0) and each of the non-inverting outputs of the flip-flops (F0 . . . Fn) being connected to the input of the first flip-flop (F0) via an XOR gate (11), characterised in that the generator comprises at least one additional logic gate (13, 14, 15; 17, 18, 19) including at least one additional flip-flop (14;18).The extra logic gates may comprise gated to toggle between the inverting end and the non-inverting outputs, or to generate an extra `0` at the output or to chop, preferably randomly, the input signal.