Would t \cdot (P_a + A_1) work for this? ie provide X, T and prove you have a t where T = t\cdot G and X = t\cdot(P_a + A_1). Then you could reveal t via an adaptor signature.
Would t \cdot (P_a + A_1) work for this? ie provide X, T and prove you have a t where T = t\cdot G and X = t\cdot(P_a + A_1). Then you could reveal t via an adaptor signature.