Communication apparatus and associated method for sending messages while concealing the messages among chaff data. In sending outgoing communications to and from a remote device, a stream of chaffing data is generated. A message to be communicated is inserted into the stream of chaffing data such that the beginning and ending boundaries of the first message are concealed by the chaffing data. A matching pair of deterministic number generators, one at the sending end and one at the remote device, are initialized using a common initialization value to cause generation of a common sequence of numbers with the remote device. The stream of chaffing data, or data associated with the first message, or both, are encoded with the common sequence of numbers.