P2B: Privacy Preserving Identity-Based Broadcast Proxy Re-Encryption

This paper proposes Privacy Preserving Identity-Based Broadcast Proxy Re-encryption (P2B) - a scheme to provide privacy preserving in identity-based broadcast proxy reencryption. P2B uses Lagrange interpolation polynomial theorem to provide privacy to identities of the receiver group of broadcasted re-encrypted ciphertext. Proxy re-encryption is an efficient solution to securely share cloud data with receivers. For sharing data with a group of receivers, the sender needs to regenerate the re-encryption key for every receiver, which leads to an overhead on the sender side. To solve the issue, identity-based proxy re-encryption is extensible to identity-based broadcast proxy re-encryption. However, the later poses a privacy issue on the receiver side, as each receiver of the receiver group needs to know the other receiver's identity. We solve the problem using the Lagrange interpolation method. We prove that our scheme is secure against chosen plaintext attack using random oracle model and it successfully hides the identities of the receivers. Finally, we implement P2B and compare it with other existing systems. It is seen that P2B reduces the decryption time by 68% than recent existing Broadcast proxy re-encryption schemes and 98% than the existing privacy preserving schemes.