Digital multisignatures improve security of digital signatures and reduce fraud by collusion. In this paper we first present a new secure signature scheme which is based on a variant of Strong Diffie-Hellman Assumption, called SDH2 assumption. Then, we extend this signature for a new multisignature scheme without interaction between users. Our proposed schemes which work in groups equipped with efficient bilinear map are provably secure without random ora-cles. We also compare our schemes with previous works.