A self-authenticating apparatus for effecting secure communication of a binary
signal. In the encipherment apparatus, key is generated as a function of plain
text summed with a pseudorandom linear sequence. The decipherment apparatus performs
a reverse function in an autokey mode. Incoming cipher text is summed with generated
key to create a plain text stream. As in the encipherment device, key is generated
as a function of the resulting plain text summed with a pseudorandom linear sequence.
