[rakoo]

It does sound similar to ideas in Tahoe-LAFS: https://tahoe-lafs.readthedocs.io/en/latest/architecture.htm...

Which has already thought about attacks on the scheme you described: https://tahoe-lafs.org/hacktahoelafs/drew_perttula.html

[ChadNauseam]

Wow, the idea of adding a key to create groups where only someone inside the group could carry out the attack is awesome.