Cryptology ePrint Archive: Report 2021/1649

A New Security Notion for PKC in the Standard Model: Weaker, Simpler, and Still Realizing Secure Channels

Wasilij Beskorovajnov and Roland Gröll and Jörn Müller-Quade and Astrid Ottenhues and Rebecca Schwerdt

Abstract: Encryption satisfying CCA2 security is commonly known to be unnecessarily strong for realizing secure channels. Moreover, CCA2 constructions in the standard model are far from being competitive practical alternatives to constructions via random oracle. A promising research area to alleviate this problem are weaker security notions—like IND-RCCA secure encryption or IND-atag-wCCA secure tag-based encryption—which are still able to facilitate secure message transfer (SMT) via authenticated channels. In this paper we introduce the concept of sender-binding encryption (SBE), unifying prior approaches of SMT construction in the universal composability (UC) model. We furthermore develop the corresponding non-trivial security notion of IND-SB-CPA and formally prove that it suffices for realizing SMT in conjunction with authenticated channels. Our notion is the weakest so far in the sense that it generically implies the weakest prior notions—RCCA and atag-wCCA—without additional assumptions, while the reverse is not true. A direct consequence is that IND-stag-wCCA, which is strictly weaker than IND-atag-wCCA but stronger than our IND-SB-CPA, can be used to construct a secure channel. Finally, we give an efficient IND-SB-CPA secure construction in the standard model from IND-CPA secure double receiver encryption (DRE) based on McEliece. This shows that IND-SB-CPA security yields simpler and more efficient constructions in the standard model than the weakest prior notions, i.e., IND-atag-wCCA and IND-stag-wCCA.

Category / Keywords: public-key cryptography / Secure Message Transfer, Authenticated Channel, Tag-based Encryption, IND-CPA, IND-CCA2, CCA2 Relaxations, Universal Composability, McEliece

Original Publication (with major differences): IACR-PKC-2022

Date: received 16 Dec 2021

Contact author: beskorovajnov at fzi de, groell at fzi de, ottenhues at kit edu, schwerdt at kit edu

Available format(s): PDF | BibTeX Citation

Note: This is the full version of the IACR PKC 2022 publication.

Version: 20211217:143041 (All versions of this report)

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