Cryptology ePrint Archive: Report 2018/1030

Registration-Based Encryption from Standard Assumptions

Sanjam Garg and Mohammad Hajiabadi and Mohammad Mahmoody and Ahmadreza Rahimi and Sruthi Sekar

Abstract: The notion of Registration-Based Encryption (RBE) was recently introduced by Garg, Hajiabadi, Mahmoody, and Rahimi [TCC'18] with the goal of removing the private-key generator (PKG) from IBE. Specifically, RBE allows encrypting to identities using a (compact) master public key, like how IBE is used, with the benefit that the PKG is substituted with a weaker entity called "key curator" who has no knowledge of any secret keys. Here individuals generate their secret keys on their own and then publicly register their identities and their corresponding public keys to the key curator. Finally, individuals obtain "rare" decryption-key updates from the key curator as the population grows. In their work, they gave a construction of RBE schemes based on the combination of indistinguishability obfuscation and somewhere statistically binding hash functions. However, they left open the problem of constructing RBE schemes based on standard assumptions.

In this work, we resolve the above problem and construct RBE schemes based on standard assumptions (e.g., CDH or LWE). Furthermore, we show a new application of RBE in a novel context. In particular, we show that anonymous variants of RBE (which we also construct under standard assumptions) can be used for realizing abstracts forms of anonymous messaging tasks in simple scenarios in which the parties communicate by writing messages on a shared board in a synchronized way.

Category / Keywords: public-key cryptography / Registration-based encryption, Identity-based encryption, Garbling, Anonymity

Date: received 23 Oct 2018

Contact author: sruthi sekar1 at gmail com, sanjamg@berkeley edu, mdhajiabadi@berkeley edu, mohammad@virginia edu, ahmadreza@virginia edu

Available format(s): PDF | BibTeX Citation

Version: 20181026:131329 (All versions of this report)

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