I want to be able to decrypt data using a network of nodes N where a certain threshold of nodes is necessary and no single node has the power to decrypt data by itself. At any given point, at minimum 2/3 of the nodes are honest and at most 1/3 of the nodes are semi-honest, except for at the initiation of the network, where we can assume all nodes are honest and trustworthy (allowing for, if necessary, some initiation logic). I want to be able to perform ECDH between my network N and an external actor A owning a keypair of the same type to generate a shared secret between these two parties for encryption. How can I best resolve this (in the best case without that trusted entity E, but also with if that's the only possible way)?
Edit: To clarify, standard SSS does not work here, because there is no party that we can trust to reconstruct the key, decrypt, and then not secretly keep the recreated key