Provably Secure Identity-Based Threshold Decryption on Access Structure

The existing provably secure threshold decryption schemes based on the Lagrange interpolation can only be applied to the (t, n) threshold structure. The first provably secure identity-based threshold decryption scheme on access structure is proposed, in which the PKG gets the adversary structure from the access structure, and then according to the adversary structure, the PKG ingeniously distributes the private key shares through the knowledge of set theory, to guarantee only the participants in the "qualified subset" can decrypt the ciphertext. The validity of the proposed scheme is proved perfectly, and the formal proof of adaptive chosen-ciphertext security is provided in the random oracle model. Compared to the existing schemes, the proposed scheme has obvious advantages on the performance of applied range and computational overhead.