Novel Inner Product Encryption Resistant to Partial Collusion Attacks

Inner product encryption (IPE) is a new cryptographic primitive initially proposed by Abdalla et al. in 2015. IPE can be classified into public-key IPE and secret-key IPE. The currently proposed PK-IPE schemes can-not resist the following collusion attack: an invalid user that holds no private key can ”buy” a combined key generated from multiple collusion adversaries, and the user can use this private key to decrypt a ciphertext. Furthermore, the user should not let the collusion adversaries know the ciphertext, and the collusion adversaries should not let the user learn their private keys. We present a new PK-IPE to resist such collusion attack. Our PK-IPE is proven secure under the selective-vector chosen-plaintext attack model. We formalize a selective vector collusion attack model to prove that our scheme is secure under this model.