Paper 2001/071 Original: eprint.iacr.org/2001/071 ↗

Multi-Recipient Public-Key Encryption with Shortened Ciphertext

Abstract

In the trivial $n$-recipient public-key encryption scheme, a ciphertext is a concatenation of independently encrypted messages for $n$ recipients. In this paper, we say that an $n$-recipient scheme has a ``{\it shortened ciphertext}'' property if the length of the ciphertext is almost a half (or less) of the trivial scheme and the security is still almost the same as the underlying single-recipient scheme. We first present (multi-plaintext, multi-recipient) schemes with the ``{\it shortened ciphertext}'' property for ElGamal scheme and Cramer-Shoup scheme. We next show (single-plaintext, multi-recipient) hybrid encryption schemes with the ``{\it shortened ciphertext}'' property.