A possible reason for not telling us how our keys will be protected.

[Tom Thomson]

If the protection to be given to our keys is really inadequate, that fact 
must be TOP SECRET since disclosure of it would be likely to cause 
severe long-term damage to the UK economy.  Maybe that's why the 
HO can't answer Brian's question? I can't think of any other reason 
apart from pure stupidity (the most likely explanatiuon, given their 
performance on this Bill).

Tom

[TOP SECRET:] The compromise of this information or material would be
likely to threaten directly the internal stability of the UK or
friendly countries; to lead directly to widespread loss of life; to
cause exceptionally grave damage to the effectiveness or security of
UK or allied forces or to the continuing effectiveness of extremely
valuable security or intelligence operations; to cause exceptionally
grave damage to relations with friendly governments; or to cause
severe long-term damage to the UK economy.