Snowden anonymously sent him an e-mail saying he had documents he wanted to share, and followed that up with a step-by-step guide on how to encrypt communications, which Greenwald ignored. Snowden then sent a link to an encryption video, also to no avail.
“It’s really annoying and complicated, the encryption software,” Greenwald said as we sat on his porch during a tropical drizzle. “He kept harassing me, but at some point he just got frustrated, so he went to Laura.”
From another source [2] I cited in another comment:
"it took Greenwald several more months and help from experts before he could learn relatively basic tools like PGP encryption."
That's not exactly trust-inspiring, I'd say.
[1] http://www.nytimes.com/2013/08/18/magazine/laura-poitras-sno...
[2] https://www.dailydot.com/layer8/edward-snowden-gpg-for-journ...