An ID-Based 2-Functional Proxy Cryptosystem

Lihua Wang, Licheng Wang, Masahiro Mambo +1 more

Woo Kwon Koo, Jung Yeon Hwang, Dong Hoon Lee

Lihua Wang, Licheng Wang, Masahiro Mambo +1 more

Proxy cryptosystems are classified into proxy decryption systems and proxy re-encryption systems on the basis of a proxy's role. In this paper, we propose an ID-based proxy cryptosystem with revocability and hierarchical confidentialities. In our scheme, on receiving a ciphertext, the proxy has the rights to perform the following three tasks according to the message confidentiality levels of the sender's intention: (1) to decrypt the ciphertext on behalf of the original decryptor; (2) to re-encrypt the ciphertext such that another user who is designated by the original decryptor can learn the message; (3) to do nothing except for forwarding the ciphertext to the original decryptor. Our scheme supports revocability in the sense that it allows proxy's decryption and re-encryption rights to be revoked even during the valid period of the proxy key without changing the original decryptor's public information. We prove that our proposal is indistinguishable against chosen identity and plaintext attacks in the standard model. We also show how to convert it into a system against chosen identity and ciphertext attacks by using the Fujisaki-Okamoto transformation.

Giles Brassard

Fengyin Li, Mengjiao Yang, Zhihao Song +2 more

Blind signatures have been widely applied when privacy preserving is required, and the delegation of blind signature rights and a proxy blind signature (Proxy-BS) become necessary when the signer cannot sign. Existing Proxy-BS schemes are based on traditional cryptographically hard problems, and they cannot resist quantum attacks. Moreover, most current Proxy-BS schemes depend on public key infrastructure (PKI), which leads to high certificate storage and management overhead. To simplify key management and resist quantum attacks, we propose a post-quantum secure identity-based proxy blind signature (ID-Proxy-BS) scheme on a lattice using a matrix cascade technique and lattice cryptosystem. Under the random oracle model (ROM), the security of the proposed scheme is proved. Security shows that the proposed scheme assures security against quantum attacks and satisfies the correctness, blindness, and unforgeability. In addition, we apply the ID-Proxy-BS scheme on a lattice to e-voting and propose a quantum-resistant proxy e-voting system, which is resistant to quantum attacks and achieves the efficiency of e-voting.

Xavier Bultel, Charlène Jojon, Pascal Lafourcade