Hi Jonas,

Seems you are right: for every tx, compute c from the on-chain data, and
the server can match the c to the m (tx). So there would need to be a
method for blinding the value of c.

On Mon, Jul 24, 2023 at 4:39 PM Jonas Nick <jonasdnick@gmail.com> wrote:

>  > Party 1 never learns the final value of (R,s1+s2) or m.
>
> Actually, it seems like a blinding step is missing. Assume the server
> (party 1)
> received some c during the signature protocol. Can't the server scan the
> blockchain for signatures, compute corresponding hashes c' = H(R||X||m) as
> in
> signature verification and then check c == c'? If true, then the server
> has the
> preimage for the c received from the client, including m.
>