In the case, Mr Justice Ouseley said that the parties could not voluntarily agree to a closed procedure - and that Parliament would have to legislate.

BBC: Secret cases: Who could be affected?

We don't know whether this is true or not - but if the case ever gets to court, the government would want to use a closed procedure to protect GCHQ's workings.

BBC: Secret cases: Who could be affected?

Smid noted that NIST's public contest to find the next generation encryption standard is a radical change from the government's previously closed procedure for adopting DES. "It's a breakthrough in the way the government and the public sector are coming up with a standard, " he said.

CNN: U.S. government to set new standard for advanced encryption

But ministers felt that they had not been able to defend themselves in this case because the Closed Material Procedure could not be used.

BBC: Analysis: A question of secret courts

Dan Nichols said treatment will begin on the HVAC system Friday night, and some streets around the building will be closed to facilitate the procedure, which is expected to take about 24 hours.

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