National Security Agency whistleblower Edward Snowden says he has ensured there is a “zero percent chance” either China or Russia could obtain access to the secret NSA documents he has given to journalists. Writing over encrypted chat, Snowden told The New York Times’ James Risen he did not keep any copies of the files after handing them to Glenn Greenwald and Laura Poitras in Hong Kong. He says he was able to prevent China from accessing the files because he was familiar with their systems after targeting them as an NSA contractor. Snowden told Risen: “So long as there’s broad support amongst a people, it can be argued there’s a level of legitimacy even to the most invasive and morally wrong program, as it was an informed and willing decision. However, programs that are implemented in secret, out of public oversight, lack that legitimacy, and that’s a problem.” Snowden also disputed an earlier New York Times report about a warning regarding his behavior placed in his personnel file in 2009 by a supervisor at the CIA. Snowden said the supervisor was retaliating against him after he warned about a software vulnerability. The CIA has also disputed The New York Times’ account.