In an interview Wednesday from a hotel in Hong Kong, she described herself as an unexpected player in the Snowden leak. “This is not something I was seeking out,” she said.

Mr. Snowden first contacted her in January, she said, telling her that he had read about her regular border scrutiny and saw it as “an indicator that I was a person who was ‘selected,’ ” that is, someone who would be familiar with what it is to be watched by the government. “He knew it was a subject that would resonate with me.” (He had also seen a short film about domestic surveillance, “The Program,” she made for The New York Times.)

Ms. Poitras, who won a MacArthur “genius” grant last year and was nominated for an Oscar for “My Country,” was already living and working outside the country. After six years of being questioned at the border — “upwards of 40 times, probably more, I lost count” — and having her laptop seized, her notes copied, she relocated to Europe.

“It was good timing in that way,” she said Wednesday.

But in addition to her tense relations with her government, there was another, more practical reason Mr. Snowden connected with her, she said. Because of her experience reporting on national security matters, Ms. Poitras said, she had the technical ability to hold an encrypted online conversation with Mr. Snowden from the start, which he insisted on.

“The number of journalists who know how to use it is very small,” she said. “You wouldn’t have been able to communicate with Snowden without encryption.”