Numbers station are short-wave radio stations that periodically broadcast streams of numbers. This is done to transmit messages to spies abroad. The streams of numbers are decrypted by the spy using a One Time Pad (OTP). This communication method has several advantages. While the origin is exposed, the receiver is almost guaranteed anonymity since the only necessary equipment is a short-wave radio and the transmission can be received in private. Assuming that the one time pads are truly random, the messages are assuredly uncrackable. One potential attack vector is traffic analysis, wherein the adversary compares message transmission with suspected receiver availability. In order, to combat this the sender must send communications regularly whether there is a message or not (fill traffic)1.