In this work, we build upon the results from CHT and Joye. We take the simple intuition from CHT, that ciphertexts can be seen as polynomials, but also demonstrate that we only need to send as much data as in the original Cocks scheme. This perspective leads to better intuition as to why these ciphertexts are homomorphic and to explicit efficient algorithms for computing this homomorphic addition.
We believe that our approach will facilitate other extensions of Cocks IBE. As an example, we exhibit a two-way proxy re-encryption algorithm, which arises as a simple consequence of the structure we propose. That is, given a re-encryption key, we can securely convert a ciphertext under one key to a ciphertext under the other key and vice-versa (hence two-way).Category / Keywords: Date: received 14 Dec 2016, last revised 23 Mar 2017 Contact author: rio at mit edu Available format(s): PDF | BibTeX Citation Note: Fixed a typo in section 3. Version: 20170323:183952 (All versions of this report) Short URL: ia.cr/2016/1150 Discussion forum: Show discussion | Start new discussion