In 2004, Abe et al. proposed a threshold signer-ambiguous signature scheme from variety of keys. Their scheme is a generalized case of the ring signature scheme, and it allows the key types to be based on the trapdoor one-way permutations (TOWP) or sigma-protocols including Schnorr's signature scheme. However, the signed message is public for all, which may result in disputes. In this paper, we present a novel threshold signer-ambiguous signature scheme, having the signed message concealed and keeping who the receivers are secret from variety of keys.
