Making Public Key Functional Encryption Function Private, Distributively

Kenneth G. Paterson, Sriramkrishnan Srinivasan

Zvika Brakerski, Gil Segev

Vincenzo Iovino, Qiang Tang, Karol Żebrowski

In the public‐key setting, known constructions of function‐private functional encryption (FPFE) were limited to very restricted classes of functionalities like inner‐product. Moreover, its power has not been well investigated. The authors construct FPFE for general functions and explore its powerful applications, both for general and specific functionalities. One key observation entailed by their results is that attribute‐based encryption with function privacy implies FE, a notable fact that sheds light on the importance of the function privacy property for FE.

Ragdah Ahmed Qasim, Hamza B. Habib, Rifaat Z. Khalaf

This article proposes a new encryption algorithm based on two cryptographic techniques which are the three-pass protocol and the Paillier cryptosystem. Using the three-pass protocol makes it possible for one party to safely send a message to another party without exchanging or distributing encryption secrets. In each pass in the proposed algorithm, each party uses their private pair of prime numbers to calculate the modular number. That means they use their public and private keys to perform the encryption and decryption. Moreover, the encryption and the decryption on the sender side are performed by the Paillier cryptosystem which is based on the difficulty of finding the inverse modular of the public key. In the proposed algorithm, less information is shared between the two parties and that makes it more secure against attacks. The results show that the proposed algorithm needs less time to perform the encryption and decryption compared with the classic algorithm. Therefore, the proposed algorithm is more secure, fast and reliable for sending and receiving data compared with the classic algorithm.

Zvika Brakerski, Gil Segev

James D Dalton

In public-key encryption, a long-term private key can be an easy target for hacking and deserves extra protection. One way to enhance its security is to share the long-term private key among multiple (say n) distributed servers; any threshold number (t, t ≤ n) of these servers are needed to collectively use the shared private key without reconstructing it. As a result, an attacker who has compromised less than t servers will still not be able to reconstruct the shared private key. In this thesis, we studied threshold decryption schemes for lattice-based public-key en- cryption, which is one of the most promising post-quantum public-key encryption schemes. We developed threshold decryption schemes for Stinson’s, the standard NTRU, and NTRU with Ring Learning with Errors (R-LWE) cryptosystems. Prototype implementations were developed for validating the functionality of these threshold decryption schemes. Our de- signs achieve heuristic security, and its security is supported by mechanisms similar to that of R-LWE.