International Association
for Cryptologic Research

The simple matrix encryption scheme (Tao-Diene-Tang-Ding, PQCrypto 2013) has a problem of decryption failures. Quite recently, Petzoldt-Ding-Wang (http://eprint.iacr.org/2016/010) proposed a new version of this scheme called the tensor simple matrix encryption scheme to remove decryption failures by using a tensor product of two small matrices as its secret key. However, it is much weaker than the original scheme. In this note, we show that the tensor simple matrix encryption scheme is equivalent to a weak version of the original simple matrix encryption scheme.