International Association
for Cryptologic Research

In this note, we describe an error in the proof for CLRW2 given by Landecker et al. in their paper at CRYPTO 2012 on the beyond-birthday-bound security for tweakable block ciphers.

We are able to resolve the issue, give a new bound for the security of CLRW2, and identify a potential limitation of this proof technique when looking to extend the scheme to provide asymptotic security.