[Resource Topic] 2023/864: Compact Lossy Trapdoor Functions and Selective Opening Security From LWE

Welcome to the resource topic for 2023/864

Title:
Compact Lossy Trapdoor Functions and Selective Opening Security From LWE

Authors: Dennis Hofheinz, Kristina Hostáková, Julia Kastner, Karen Klein, Akin Ünal

Abstract:

Selective opening (SO) security is a security notion for public-key
encryption schemes that captures security against adaptive corruptions
of senders. SO security comes in chosen-plaintext (SO-CPA) and
chosen-ciphertext (SO-CCA) variants, neither of which is implied by
standard security notions like IND-CPA or IND-CCA security.

In this paper, we present the first SO-CCA secure encryption scheme that
combines the following two properties: (1) it has a constant ciphertext
expansion (i.e., ciphertexts are only larger than plaintexts by a constant
factor), and (2) its security can be proven from a standard assumption.
Previously, the only known SO-CCA secure encryption scheme achieving
(1) was built from an ad-hoc assumption in the RSA regime.

Our construction builds upon LWE, and in particular on a new and surprisingly
simple construction of compact lossy trapdoor functions (LTFs).
Our LTF can be converted into an “all-but-many LTF” (or ABM-LTF),
which is known to be sufficient to obtain SO-CCA security. Along the
way, we fix a technical problem in that previous ABM-LTF-based construction
of SO-CCA security.

ePrint: https://eprint.iacr.org/2023/864

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