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Understanding 3rd party (D)KDM creation

Posted: Sun Mar 08, 2020 9:14 am
by IberianDragon
Hi,

I've made a decent number of DCPs now but to date they've all been unencrpyted. Pretty soon I am going to need to make one for a distributor who (understandably) requires it to be encrypted. Given they will be the ones that will deal directly with cinemas, I'm assuming that they (or an appointed agent) will be responsible for making KDMs.

I'm assuming that it's not simply a case of ticking the 'encrypted' option when making the DCP and that I'll need something from the distributor in order to make one that they can later generate KDMs?

Re: Understanding 3rd party (D)KDM creation

Posted: Sun Mar 08, 2020 1:55 pm
by Carsten
The distributor needs to have their own KDM distribution system (it could be their own DCP-o-matic installation/KDM creator, or any other suitable software). This system must be able to export a certificate (.pem file) which they will have to send to you. You need to import this .pem file into your DCP-o-matic installation. From then on, you are able to create (D)KDMs for THEIR system. These DKDMs then allow them to create further KDMs towards cinema screens.

Once you start creating encrypted DCPs, you have to keep a special discipline maintaining your own certs and keys. They are part of the DCP-o-matic prefs. DCP-o-matic will give you some hints when enabling encryption.

I suggest to always start with the latest stable release (2.14.x currently). For the first time you create an encrypted DCP, first go to 'Preferences'-> 'Keys'->'Advanced'->'Remake certificates and key', to recreate all keys and certs once. This is to make sure you have a clean start. Make sure your computer is on current date at least.

Then, restart DCP-o-matic and immediately backup your certs and keys, individually from within DCP-o-matic (name them in a useful way), and additionally, create a full backup of your prefs folder (this is the easiest way to backup your certs). e.g. you can right-click on your DCP-o-matic prefs/settings folder and choose 'Send to compressed (ZIP) folder' (WIN) or 'Archive' (Mac), or whatever Linux offers you. Then store away this ZIP to a (better multiple) safe place. This will allow you to recreate your config easily in the future (e.g. after a fresh DCP-o-matic installation, disc crash, etc.).
I usually rename this Backup ZIP by adding the DCP-o-matic version number to it, so I may end up with a couple of backups over time. (e.g. dcpomatic_2_14_26.zip). This could become handy if prefs don't survive and update, or you need to supply a specific prefs file to a specific installation. I am just overcautious here, but, it costs you nothing.

https://dcpomatic.com/manual/html/ch19.html


Also, for every feature you create encrypted, you should always and immediately create a DKDM for your own installation (under 'Jobs'-> 'Make DKDM for DCP-o-matic...') . That will allow you to create new (D)KDMs even if your DCP project files are lost/deleted. These DKDMs are stored within those mentioned prefs that you will hopefully backup regularly.


- Carsten

Re: Understanding 3rd party (D)KDM creation

Posted: Sun Mar 08, 2020 2:47 pm
by IberianDragon
Thank you so much for such a detailed reply, Carsten!

So, do I need this certificate before I make the encrypted DCP or only at the point of making the DKDM?

Re: Understanding 3rd party (D)KDM creation

Posted: Sun Mar 08, 2020 3:37 pm
by Carsten
You can create THEIR DKDM later at any time - but until then, you need to keep the project folder and encrypted DCP within, or, create your own local DKDM immediately. Better, both.

Wondering wether we should have an option in DCP-o-matic to automatically create a local DKDM whenever an encrypted DCP/CPL is finished?

- Carsten