Multi-recipient Encryption in Heterogeneous Setting

This paper presents an efficient method for securely broadcasting a message to multiple recipients in a heterogeneous environment where each recipient is allowed to choose his or her preferred secure encryption scheme independently of other recipients' choices. Previous work pertinent to this direction of research, namely multi-recipient encryption scheme (MRES), generally requires all recipients adhere to the same public key encapsulation mechanism (KEM) for the sake of delivering promised savings in computation and bandwidth via randomness reuse. Our work eliminates the requirement of using the same KEM by all recipients, whereby removing a practical barrier to the adoption of MRES in real world applications. A second advantage is the method's capability to cope with a dynamically changing group of recipients where old recipients may be deleted and new recipients may be added, while ensuring the security of messages shared in future. Additional features of our method include decryption by a sender, anonymity of recipients and stateful key encapsulation which significantly reduces computational costs for securely transmitting or sharing new messages. All these attributes would be useful in building applications for secure data sharing in a cloud computing environment.