BROOKE GLADSTONE: On Tuesday, the CIA declassified the government’s six oldest classified documents dating from 1917 and 1918. According to the CIA’s news release, quote, “These documents, which describe secret writing techniques and are housed at the National Archives, are believed to be the only remaining classified documents from the World War I era.” Now, this raises a couple of questions, at least. Why does the U.S. government [LAUGHING] still have classified documents from World War I? And secret writing techniques? Here to answer [LAUGHS] those questions, and maybe tell us how to open a sealed letter without tearing the envelope, is Spencer Ackerman, senior reporter from Wired.com’s national security blog, Danger Room. Spencer, welcome to the show.

SPENCER ACKERMAN: Thanks for having me.

BROOKE GLADSTONE: So when you read that first news release, were you surprised?

SPENCER ACKERMAN: Stunned would probably be [BROOKE LAUGHS] a better way of [LAUGHS] describing it.

BROOKE GLADSTONE: These particular documents describe espionage techniques used by the Office of Naval Intelligence during the First World War, including recipes for making invisible ink.

SPENCER ACKERMAN: Yes, this was state-of-the-art technology for your World War I-era spycraft. It’s a series of recipes for how you would concoct ink that you couldn't read without doing some kind of treatment to the paper or to the ink itself, how to open a letter without its intended recipient knowing or, in other cases, how to tell if there are secret messages that the untreated eye would not be able to detect.

BROOKE GLADSTONE: Some of these documents are really quaint. Like one of them suggests that a solution of sodium nitrate and starch in water could be carried, for example, in handkerchiefs or starched collars.

SPENCER ACKERMAN: It’s important to remember here that this is an artifact of the time before the United States really had a robust intelligence apparatus. For the past 60 years we've had multiple and multiplying intelligence agencies whose budgets total up to 80 billion dollars annually, but back in World War I there was pretty much postal inspectors, the Office of Naval Intelligence. The FBI, which isn't involved in these techniques, was barely 15 years old. It’s a weird thing to encounter in this day and age that these documents would really look like state-of-the-art spycraft for, you know, precisely the reasons you’re mentioning.

[BROOKE LAUGHS] We're seeing recipes for, you know, a few CCs of sulfuric acid, sugar and heat as a way of keeping secrets.



BROOKE GLADSTONE: There was an assistant chemist at the Department of Commerce named A.M. Heinzelmann who had concocted several recipes for invisible ink, and he noted that one of them could, he said, quote, “exert a very corrosive action on steel pens, and therefore, if suitable in other respects, it would be better to use a quill.”

SPENCER ACKERMAN: Yes, so we're not [LAUGHS] even talking about state-of-the-art penmanship -

[BROOKE LAUGHS] - and inking techniques from 1917 and 1918. We're going really, really far back. I mean, what’s so amazing about these documents is how far into the future they've been stamped as requiring to remain secret. The document that you just read has an annotation from March 15th, 1976, saying that it has to be re-graded secret, and then that’s crossed out, and over which is written “confidential.” So that’s got to still remain secret, even after all of these techniques have been vastly overtaken by advances in secrecy.

BROOKE GLADSTONE: Why? You can go online or to the back of a comic book and get more effective invisible ink.

SPENCER ACKERMAN: [LAUGHS] Well, this becomes the subject of a lawsuit ten years ago between some declassification advocates and the CIA, and that’s where we get probably our only real explanation for why they have to remain secret. And that comes from a court filing in March of 1999 from a woman named Teresa Wilcox, who is the Information Review Officer at the Directorate of Science and Technology for the CIA, in response to a lawsuit filed by an individual named Mark Zaid. What Ms. Wilcox said to the court was that the unauthorized disclosure of the intelligence methods specified in these documents could jeopardize the security of the CIA’s more modern systems of covert communication because they were, in fact, quote, “in part derived from the formulas in these documents.” She goes on to suggest at a different point that these methods are, quote, “currently viable [BROOKE LAUGHS] for use by CIA agents.” So, you know, which would you have it? Either they’re the historical antecedents of some concealment techniques still in use or theoretically [LAUGHS] they're being used now. That’s been the rationale of record until suddenly CIA Director Panetta decided to disclose them this week.

BROOKE GLADSTONE: And in that official news release I mentioned, Panetta was quoted as saying, “These documents remained classified for nearly a century until recent advancements in technology made it possible to release them.” So, what are those advancements?

SPENCER ACKERMAN: They [LAUGHS] don't exist.

[BROOKE LAUGHS]] It’s not the most credible position taken by Director Panetta. The CIA denies this, but the lawsuit I just mentioned has been going on for quite a while. And recently Zaid and one of his colleagues filed an interbureaucratic filing requesting a mandated disclosure. That happened in 2009 and that got appealed to something called the Interagency Security Classification Appeals Panel, which is just meant to make sure that, that the government doesn't needlessly overclassify information. And Zaid and his colleagues believe that a decision to mandate disclosure of this information was imminent and, and the CIA got out ahead of it.

BROOKE GLADSTONE: Do you think that these secrets now revealed mean we're less safe?

SPENCER ACKERMAN: No.

[BROOKE LAUGHS] It’s impossible to [LAUGHS] credit that suggestion. I think that terrorists learning about how to spray some ink with lemon juice and heat an envelope, you know, in order to reveal a hidden message is probably not going to result in any gigantic national security disaster.

BROOKE GLADSTONE: What is the CIA’s best method for opening a sealed envelope?

SPENCER ACKERMAN: You know, if I disclose that they'll - they'll kill me.

BROOKE GLADSTONE: [LAUGHS] Spencer, thank you very much.

SPENCER ACKERMAN: Thank you very much for having me.

BROOKE GLADSTONE: Spencer Ackerman is senior reporter for Wired.com’s national security blog, Danger Room.

[CLIP FROM THE OFFICE]:

RAINN WILSON PORTAYING DWIGHT SCHRUTE: The invisible ink will reveal that everyone should meet at the warehouse immediately. Do not ask me where I got the invisible ink. [PAUSE] Urine. It was urine.

[END CLIP]

BROOKE GLADSTONE: That’s Dwight Schrute, pencil-pusher and would-be spymaster from The Office on NBC.

[MUSIC UP AND UNDER]

BOB GARFIELD: That's it for this week's show. On the Media was produced by Jamie York, Mike Vuolo, Nazanin Rafsanjani, Alex Goldman, P.J. Vogt and Sarah Abdurrahman, and it was edited – by Brooke. Our technical director is Jennifer Munson, and she had help this week from Rob Granniss.

BROOKE GLADSTONE: Katya Rogers is our senior producer. Ellen Horne is WNYC’s senior director of National Programs. Bassist/composer Ben Allison wrote our theme. On the Media is produced by WNYC and distributed by NPR. I'm Brooke Gladstone.

BOB GARFIELD: And I’m Garth Barfield.

BROOKE GLADSTONE: [LAUGHS]