Recover encrypted DCP given test KDM

[NiQ]

Hi,
So I have an issue with an old encrypted DCP where the unencrypted original has been lost. There is however a test KDM which was targeted at a software player (VLC) and its private somehow survived. Both the KDM and the certificate have expired but since that's a software player we're talking about it doesn't really matter.
So it's possible to play the DCP - but is it possible to decrypt it and save it unencrypted?

[Carsten]

It is new to me that VLC supports encrypted DCPs and KDMs, but a quick google search seems to suggest it is indeed possible.


Now, expired KDMs are a problem on real DCI systems where the expiration is based on a secure hardware clock that can not be altered. For a software player, there are two possibilities:

- the software player simply ignores the time window in the KDM
- the software player can be lead to trust a system clock set backwards into the KDM validity window


For DCP-o-matics' player, you can set in prefs wether the player ignores validity timeframes or not. This is just a test feature, so you can actually check KDM time frames.

The only thing necessary to decrypt a DCP is the actual encryption key.

That said, I have no idea about the inner workings of the VLC KDM code.

- Carsten