The CIA lifted the lid on one corner of the cloak and dagger world of World War I, declassifying six of the oldest secret documents in the U.S. government archives, the agency announced Tuesday.
The documents show top techniques used by spies, generals and diplomats to send secret messages in a diplomatic war that raged long after the guns stopped. The records reveal how invisible ink was used to send word between allies, and spies learned to open letters to read each others' secrets without leaving a trace.
There's even a document written in French of the German's secret ink formula, showing the French had cracked the enemy's code.
http://news.yahoo.com/s/ap/20110419/ap_on_re_us/us_cia_secret_writing
