3
$\begingroup$

As I understand it, cryptosystems based on LWE/Ring-LWE are typically only IND-CPA, and fail to satisfy IND-CCA2. In fact, it appears that chosen ciphertext attacks could allow secret key recovery (!).

What is the best known IND-CCA2 secure encryption algorithm based on (Ring-)LWE? What about key exchange?

$\endgroup$
  • $\begingroup$ I think that having homomorphic properties precludes the ability to have IND-CCA2 status in general; I wish I had a better reference then this, but I can't seem to find one right now. $\endgroup$ – Ella Rose Jun 14 '17 at 1:12
  • $\begingroup$ @EllaRose I know. I don't need or want homomorphic properties. $\endgroup$ – Demi Jun 14 '17 at 1:16
3
$\begingroup$

If you don't mind relying on random oracles, the simplest approach is to apply a generic transformation such as Fujisaki-Okamoto to the (Ring-)LWE based scheme you start from. See for example Peikert's PQCrypto'14 paper for a concrete instantiation, and the TCC 2016 paper of Targhi and Unruh for a proof of security of this type of transform in the quantum random oracle model.

Lattice-based CCA2-secure encryption in the standard model is usually obtained using lattice trapdoors. The state-of-the-art construction is due to Micciancio and Peikert (section 6.3 of this EUROCRYPT 2012 paper).

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.