Efficient CCA-secure public-key encryption schemes from RSA-related assumptions

Abstract

We build new RSA-based encryption schemes secure against adaptive chosen-ciphertext attack (CCA-secure) without random oracles. To do this, we first define a new general RSA-related assumption, the Oracle RSA-type assumption, and give two specific instances of this assumption. Secondly, we express RSA-based encryption schemes as tag-based encryption schemes (TBE), where the public exponent is the tag. We define selective-tag weak chosen-ciphertext security for the special RSA-based case and call it selective-exponent weak chosen-ciphertext security. RSA-based schemes secure in this sense can be used as a building block for the construction of chosen-ciphertext secure encryption schemes using a previous technique. We build two concrete CCA-secure encryption schemes whose security is based on the two concrete Oracle RSA-type assumptions respectively, and whose efficiency is comparable to the most efficient CCA-secure schemes known.