[GreenKeys] Crypto story

[Jim Haynes]

This is in the book "Old Wires and New Waves" by Alvin F. Harlow, mid
1930s.  All about the state of communications systems when it was written.

He says that at the end of WW-I the Signal Corps had a show-and-tell for
the press of all the neat stuff developed during the war.  One of which
was the Vernam cipher machine.  It uses a one-time tape of random key to
produce an unbreakable message.  This involves doing an exclusive-OR
operation on each of the five code levels between the message tape and
the key tape.

Except for the demo they did some leg pulling.  The told the press they
had developed a machine that could translate French into English and
vice versa.  Demonstrated by putting a tape of English text in as the
message tape and having the French equivalent come out the printer.

Of course what they had actually done was make a piece of English text
and then make a translation into French such that both contained exactly
the same number of characters.  Then they had hand-constructed a key tape
such that each character from the English tape was converted to the
correct character for the French translation.  And if they put the French
text as input it would be converted back to English.