Research On Anonymous Multi-recipient Signcryption

The method of multi-recipient signcryption can use only one signcryption processto achieve both encryption and signature, and complete the goal of sending the samemessage to multiple authorized recipients, which has higher computational efficiencyand lower communication costs than methods of―sign-then-encrypt‖and―one to one‖,thus has wide application. In order to meet the attention of people on personal privacy,anonumous multi-recipient scheme is proposed. However, most of the existingmulti-recipient signcryption schemes do not take the anonymity of recipients intoconsideration because the list of the identities of all recipients must be included in theciphertext as a necessary element for decryption. Although the sender’s anonymity hasbeen taken into account in several alternative schemes, these schemes often suffer fromthe cross-comparison attack and joint conspiracy attack. That is to say, there are fewschemes that can achieve complete anonymity for both the sender and the recipient.However, in many practical applications, such as network conference, both thesender’s and the recipient’s anonymity should be considered carefully. Motivated bythese concerns, we propose two novel multi-recipient signcryption schemes withcomplete anonymity. The new schemes can achieve both the sender’s and therecipient’s anonymity at the same time. Each recipient can easily judge whether thereceived ciphertext is from an authorized source, but cannot determine the real identityof the sender, and at the same time, each participant can easily check decryptionpermission, but cannot determine the identity of any other recipient. The scheme alsoprovides a public verification method which enables anyone to publicly verify thevalidity of the ciphertext. When compared with exsiting multi-recipient schemes, theproposed schemes have more advantage in terms of computation complexity,ciphertext length and performance, which makes it more suitable for practicalapplications. The proposed schemes could be used for network conferences, paid-TVor DVD broadcasting applications, and solve the problem of message security andusers’ privacy leak.