Let's say I have an application that accesses an encrypted datastore, and I want the admins to be able to unlock the datastore upon application startup (and then the application will have access to the datastore until it terminates). I don't want any single admin to have the ability to unlock the datastore himself, but I also don't want all of the admins to be required to do it (since they may not always be available) -- I'd like a certain subset of admins to be able to unlock the datastore by entering their credentials.
For example, if I have 5 administrators for the application, I might want any two or three of them to be able to enter their passphrase to unlock access to the datastore.
Is there some off-the-shelf software implementation for a system like this?
This seems similar to a bifurcated key, but instead of requiring both people to supply their half of the key, I'd like any specified subset of users to be able to unlock the key.