A KDM is a decryption key made for a cinema server/player that can only play the DCP.
A DKDM is a KDM made for Easydcp creator + and similar programs that can do versioning like adding subtitles, change audio language, and add logo reels to DCPs.
When a distributor buys a DCP for versioning it is often encrypted and you can buy a DKDM that lets you do versioning on it. When the new version is ready you can encrypt it again.
It is possible to get the public encryption keys from cinemas that will screen a movie. I mostly send encrypted DCPs to cinemas in Norway via Unique Movie transit and let them handle the logistics of generating and sending KDMs to the cinemas. It is no extra cost to let them handle the KDMs.
This is how I make an encrypted DCP and a DKDM for a DCP lab or Movie Transit.
Convertering a DCP to an encrypted DCP in Easydcp Creator +
To enable encryption I click on the key on the video track and choose Enable for all tracks.
Now the lock icon is locked
To make the encrypted DCP I click on Generate Package
Choose Create DCP digest in the Generate Package Wizard
To make a test KDM you can first make a KDM for your copy of Easydcp Creator.
Open the encrypted DCP in Easydcp creator. The keys are red and the DCP is locked.
Export the Public encryption key File – Content decryption – Export public certificate
Making a KDM/DKDM in Easydcp Generator
In KDM Generator choose the DCP-Digest that was created when the DCP was created. Choose the public certificate that you exported from Easydcp Creator and choose valid dates and then click on Generate KDM
In Easydcp Creator choose Export the Public encryption key File – Content decryption – Load Content Keys and load the KDM you generated.
Now the DCP has green lock icons and the DCP is unlocked.
When I generate the DKDM for Movie Transit I use the public certificate they sent me and generate a key for them in KDM generator.