Der Spiegel releases a large trove of documents that "reveal the encryption programs the NSA has succeeded in cracking, but, importantly, also the ones that are still likely to be secure. Although the documents are around two years old, experts consider it unlikely the agency's digital spies have made much progress in cracking these technologies." The documents suggest that NSA efforts to decrypt "Pretty Good Privacy [PGP], which is still the most common encryption program for emails and documents in use today" remain unsuccessful. Similarly, off-the-record [OTR] chatting "at least sometimes makes communications impossible to read for the NSA." The documents reveal that Virtual Private Networks (VPN), which were thought to provide significant privacy, are much more exploitable than previously thought. Jake Appelbaum and Laura Poitras discuss the documents during a presentation at Chaos Communication Congress in Hamburg.