In order to access Snowden’s data, Russian security services would therefore need him to provide the encryption keys, which he does not seem likely to give up voluntarily. His supporters have cast him as an altruistic whistle-blower; handing over secrets to the Russian government would seem to undermine the values of transparency that he extols.

So Gordievsky believes Snowden would have gotten roughly the same treatment that the KGB spy got back in 1985. “They would have fed him something to loosen his tongue,” Gordievsky says by phone from the U.K., where he has been living in exile for nearly three decades. “Many different kinds of drugs are available, as I experienced for myself.” Having been called back to Moscow, Gordievsky says his KGB comrades drugged him with a substance that “turned out his lights” and made him “start talking in a very animated way.” Although the drug wiped out most of his memory of the incident, the parts he did recollect horrified him the following morning, when he woke up feeling ill. “I realized that I had completely compromised myself,” he says.

One of the substances the KGB used for such purposes at the time was called SP-117, which is odorless, tasteless and colorless, according Alexander Kouzminov, a former Russian intelligence operative who describes the drug’s effectiveness in his book, Biological Espionage. Now living in New Zealand, Kouzminov worked in the 1980s and early 1990s for the Foreign Intelligence Service, the spy agency known as the SVR, which handles undercover agents, or “illegals,” stationed in foreign countries. In his book, Kouzminov writes that various drugs were used periodically to test these operatives for signs of disloyalty or diversion. Once the drug had worn off, the agents would have no recollection of what they had said and, if their test results were satisfactory, they could be sent back into the field as though nothing had happened.