May it be possible that the trusted third party knows the parties' private keys in an "ideal model" of a Secure multiparty computation protocol? May it be possible that the trusted third party knows the parties' private keys in an “ideal model” of a Secure multiparty computation protocol?
I wonder if it may be possible that a trusted third party knows the private keys (e.g. the encryption's private key or the digital signature's private key) in an &quot;ideal model&quot; counterpart of a Secure MPC protocol.
The trusted third party may use such knowledge to simulate authenticated (and publicly verifiable) payments from one party to another, etc...
Yes.
Trusted party setup is just way to think about what the end goal of a particular MPC system is. So you may start with a party (lets call it the dealer) that sends it's private key to the trusted party, and then the trusted party uses it to commit a transaction.
Now replace the trusted party with a multi-party setup. The dealer here sends shares of its private key to each of the parties. The parties then can regenerate the private key or commit a transaction with it.