There’s an embedded archive file called all.7z which contains thousands of additional emails and files.
The 7zip archiver in which this is stored uses 256 bit AES encryption. It’s a tough nut to crack.
“FOIA” chose this most likely because there are no effective tools for 7zip, while there seem to be many for standard .zip and .RAR files.
[...]
But supposing he then sent the passphrase to Phil Jones and M Mann with a threat; Resign now, get the hell out, otherwise this passphrase goes online to the general public. That is a strategy that might push FOIA’s enemies out without completely disgracing the “scientific community”
Climategate 2.0: It Even Comes with a Pandora's Box
... Oh My: