Revocable IBE with Decryption Key Exposure Resistance from NTRU Lattice

Revocable identity-based encryption (RIBE) adds a key revocation mechanism to traditional identity-based encryption (IBE), enabling dynamic key management for key management or key expiration. To mitigate the damage to the confidentiality of all ciphertexts from short-term decryption key leakage, decryption key exposure resistance is proposed for RIBE, protecting other time periods’ ciphertexts. However, lots of high dimensional public key matrices and long ciphertexts are applied in lattice-based RIBE schemes with DKER, which leads to high computational overhead and high communication overhead. By replacing short basis trapdoor with NTRU trapdoor, revocable IBE with decryption key exposure resistance from NTRU lattice is proposed, which reduces the dimensions of public key matrices and shortens ciphertexts, thereby achieving higher efficiency. Additionally, under the RLWE assumption, RIBE with DKER from NTRU lattice is proved to be selective identity secure in the standard model.