Secrecy (especially government secrecy) has often been condemned. A 1956 book by Bertram David Wolfe, Six keys to the Soviet system, describes Soviet government this way: “Everything is done in secret. Secrecy is the breeding ground of tyranny. Secrecy is the opposite of democracy.”
 
American science fiction writer Robert A. Heinlein (1907-1988) is often cited for this 1967 line: “Secrecy is the keystone of all tyranny.” Heinlein changed the line slightly, in a 1973 story, to: “Secrecy is the beginning of tyranny.”
 
   
Wikipedia: Robert A. Heinlein
Robert Anson Heinlein (July 7, 1907 – May 8, 1988) was an American science fiction writer. Often called “the dean of science fiction writers”, he was one of the most popular, influential, and controversial authors of the genre. He set a high standard for science and engineering plausibility and helped to raise the genre’s standards of literary quality. He was one of the first writers to break into mainstream, general magazines such as The Saturday Evening Post, in the late 1940s, with unvarnished science fiction. He was among the first authors of bestselling, novel-length science fiction in the modern, mass-market era. For many years, Heinlein, Isaac Asimov, and Arthur C. Clarke were known as the “Big Three” of science fiction.
 
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Six keys to the Soviet system
By Bertram David Wolfe
Boston. MA: Beacon
1956
Pg. 117:
Everything is done in secret. Secrecy is the breeding ground of tyranny. Secrecy is the opposite of democracy. Secrecy in government means that every Communist government is neither more nor less than a conspiracy against its own people.
   
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The past through tomorrow; ‘Future history’ stories
By Robert A Heinlein
New York, NY: Putnam
1967
Pg. 401:
Sometimes I would glance over my shoulder to see who was watching me, frightened in spite of myself. I began to sense faintly that secrecy is the keystone of all tyranny. Not force, but secrecy . . . censorship. When any government, or any church for that matter, undertakes to say to its subjects, “This you may not read, this you must not see, this you are forbidden to know, the end result is tyranny and oppression, no matter how holy the motives.
       
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Time enough for love, the lives of Lazarus Long; a novel
By Robert A Heinlein
New York, NY: Putnam
1973
Pg. 366:
Secrecy is the beginning of tyranny. The greatest productive force is human selfishness. Be wary of strong drink. It can make you shoot at tax collectors.
 
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Robert A. Heinlein
By Joseph D Olander and Martin H Greenberg
New York, NY: Taplinger Pub. Co.
1978
Pg. 176:
“At any rate, our young hero Lyle also discovers that “secrecy is the keystone of tyranny. Not force, but secrecy…censorship.”