Efficient ID-based multi-receiver threshold decryption

Threshold decryption allows a message encrypted under a public key to be read only when a quorum of users cooperate to decrypt the ciphertext. However, such threshold decryption scheme does not apply well in the situation where all the users have their own public/private key pairs, but not share any private key associated with a public key, such as mobile ad hoc network featured by its dynamic character. An immediate way to achieve threshold decryption in this situation is to split the message into pieces, then encrypt these pieces under the public keys of different users. However, it is not efficient. In this paper, we propose an efficient identity based multi-receiver threshold decryption scheme that could be applied efficiently in the above situation. We also define the security notions and prove the security in random oracle model. At last, we add the broadcast feature to the scheme, such that a message could be broadcast to any number of groups.