At the core, there seems to be just a PKI for RSA keys in terms of "yes, X is a friend of mine" attestations, not unlike the PGP web of trust. So I'm optimisti

At the core, there seems to be just a PKI for RSA keys in terms of "yes, X is a friend of mine" attestations, not unlike the PGP web of trust. So I'm optimistic that your distributed singing sessions (e.g.) could use the DSNP infrastructure.