International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: RSA-OAEP is Secure under the RSA Assumption

Eiichiro Fujisaki
Tatsuaki Okamoto
David Pointcheval
Jacques Stern
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Abstract: Recently Victor Shoup noted that there is a gap in the widely-believed security result of OAEP against adaptive chosen-ciphertext attacks. Moreover, he showed that, presumably, OAEP cannot be proven secure from the {\it one-wayness} of the underlying trapdoor permutation. This paper establishes another result on the security of OAEP. It proves that OAEP offers semantic security against adaptive chosen-ciphertext attacks, in the random oracle model, under the {\it partial-domain} one-wayness of the underlying permutation. Therefore, this uses a formally stronger assumption. Nevertheless, since partial-domain one-wayness of the RSA function is equivalent to its (full-domain) one-wayness, it follows that the security of RSA--OAEP can actually be proven under the sole RSA assumption, although the reduction is not tight.
  title={RSA-OAEP is Secure under the RSA Assumption},
  booktitle={IACR Eprint archive},
  keywords={cryptographic protocols /},
  note={ 11471 received 27 Nov 2000, last revised 29 May 2001},
  author={Eiichiro Fujisaki and Tatsuaki Okamoto and David Pointcheval and Jacques Stern},