SD programmes are normally encrypted as they are recorded. They are
decrypted either by the Humax when they are copied to a USB stick, or
by the operator using the 'webif' interface of the CF. Navigating to a
programme in the Browse section, and right-clicking, brings up a menu,
of which Decrypt is one option. Transferring the resulting files using
FTP protocol (yes, I know that the 'P' stands for protocol already)
will copy a viewable set of files to your PC. VLC will always show them
if they are good.
Encrypted programmes can only be played back on the same motherboard as
was used when tehy were first recorded, so if you decrpyt any, delete
the originals and save the decrypted ones, just in case of a motherboard
failure.
HD programmes are also encrypted as they are recorded, but they have
flag, which, once set, is almost impossible to unset. This is what
'Foxy' was for. But the CF allows you to prevent the setting of the
flag, using the package 'auto-unprotect', which then allows decrypting
in the same manner as an SD recording.
As to why encryption is done in the first place, I have no idea!
Hope this helps,
--
Davey.