I want to deploy a new signing scheme for the Ethereum transactions as an alternative to the currently implemented ECDSA. This will be for future research purposes on post-quantum signing schemes. The alternative signing scheme exists as C code.
The first approach now was to replace ECDSA in one of the Ethereum client implementations like go-ethereum. Another idea was designing a smart contract containing the logic for the signing which will be executed every time a transaction is performed beforehand. As I understood, it is not (so easily) possible to execute external codes / programs in smart contracts. So the only way would be the protocol change with a later needed fork of it?
I hope there is a way, maybe you have another idea.