[cstavish]

Lee's mailing a bootable USB with Tails on it to Greenwald seems super risky. I get that Greenwald isn't a tech savant, but instructing him to make his own bootable drive after verifying checksums of the OS image would probably have been a much better look, no?

[subway]

There are a number of both secure and insecure schemes for this, all depending on how secure you deem your communication channels.

At the end of the day, you really need to send the data and/or checksums across enough independent channels that you can be statistically certain the recipient has more valid/secure data/checksums than invalid.