http://www.nytimes.com/2013/09/06/us/nsa-foils-much-internet...
Because strong encryption can be so effective, classified N.S.A. documents make clear, the agency’s success depends on working with Internet companies — by getting their voluntary collaboration, forcing their cooperation with court orders or surreptitiously stealing their encryption keys or altering their software or hardware.
N.S.A. documents show that the agency maintains an internal database of encryption keys for specific commercial products, called a Key Provisioning Service, which can automatically decode many messages. If the necessary key is not in the collection, a request goes to the separate Key Recovery Service, which tries to obtain it.
How keys are acquired is shrouded in secrecy, but independent cryptographers say many are probably collected by hacking into companies’ computer servers, where they are stored. To keep such methods secret, the N.S.A. shares decrypted messages with other agencies only if the keys could have been acquired through legal means. “Approval to release to non-Sigint agencies,” a GCHQ document says, “will depend on there being a proven non-Sigint method of acquiring keys.”
Sounds like there are plenty of possibilities: they have agents working at verisign/they broke into verisign (either physically or electronically)/they just asked and verisign said ok/they used legal processes.
They used a secret legal process. There, fixed that one for you!
Quoting Julian Assange: I have been told actually that VeriSign... has actually given keys to the US government. Not all, but a particular key.
Very interesting.