International Association
for Cryptologic Research

Recently, Gligoroski et al. proposed code-based encryption and signature schemes using list decoding, blockwise triangular private keys, and a nonuniform error pattern based on

``generalized error sets.\" The general approach was referred to as \\emph{McEliece in the World of Escher.} This paper demonstrates

attacks which are significantly cheaper than the claimed security level of the parameters given by Gligoroski et al. We implemented an attack on the proposed 80-bit parameters which was able

to recover private keys for both encryption and signatures in approximately 2 hours on a single laptop. We further find that increasing the parameters to avoid our attack will require parameters to grow by almost an order of magnitude for signatures, and (at least) two orders of magnitude for encryption.