You must be careful when using encryption not to lose important keys.
If you are making KDMs from a DCP-o-matic film you
must ensure that you have a backup of the
metadata.xml file from the project, as well as the DCP
If you are using a DKDM you must ensure that you
have a backup of DCP-o-matic's
config.xml file, since it
contains the only key which can decrypt the DKDM. The
config.xml file location depends on your operating
system; possible locations are listed in Chapter 19, Configuration files.