Comment by mihaaly

Maybe hijack the key and message before it gets distributed. Or just get after the pieces themselves if they are from Chinese or Russian authorities. Or just threaten to close the local data center if they do not collect the pieces from elsewhere, see if they can be convinced to hand over what they have, regardless where they put it.

We can be null in cryptography, but handing over both the secret and the key to this secret to the very same person is quite a trustful step, even when they say 'I promise I will not peek or let others peek, pinky promise!' - with an 'except if we have to or if we change our mind' in the small prints or between the lines.