Group-oriented setting's multisigncryption scheme with threshold designcryption

Signcryption supports the authenticity and confidently in a single logic step and it has more efficient cost than the signature-then-encryption approach. Currently signcryption schemes only support a peer to peer secure message transfer between single users, and thus it cannot be adapted to the group users in multiple senders and receivers. In this paper, we propose a group-oriented multisigncryption scheme with threshold designcryption in multi-users setting, which combines the threshold secret sharing technology, zero knowledge proof for the bilinear map equality of two discrete logarithms, multi-signature and identity-based signcryption schemes. The ciphertext in the proposed scheme is computed by all the m members in sender group, and it can be decrypted only by t-out-of-n members in receiver group. We prove the security of the proposed scheme in several models including semantic security, unforgeability, public ciphertext authenticity and verifiability.