Certificateless Broadcast Proxy Re-encryption With Group-Oriented Model

The major concept of certificateless cryptosystem is to remove the certificate in public-key cryptosystem and solve the key escrow drawback in the ID-based scheme. For the privacy protection in the public cloud environment, the proxy re-encryption scheme was developed to allow a semi-trusted proxy to transform a ciphertext under one person’s public key into other ciphertext under another person’s public key without decryption. Nowadays, many related applications of certificateless proxy re-encryption scheme have been proposed. However, most of certificateless proxy re-encryption schemes allow only a single receiver, which means for more receivers, re-transforming the ciphertext multiple times is needed. This paper introduces a novel notion of proxy re-encryption in which the sender can broadcast the re-encrypted ciphertext to a group of receivers through the proxy’s assistance based on certificateless public key cryptography. The proposed scheme has the property of constant-size re-encryption key and ciphertext, and is particularly suitable for the application executing in the enormous cloud networking.