Comment on “Highly Efficient Linear Regression Outsourcing to a Cloud”

We show that Chen et al.'s schemes [IEEE TCC, 2(4), 2014, 499-508] for outsourcing linear regression computation to the cloud are not unquestioned. In scheme 1, the client has to generate an orthogonal matrix. Its computational complexity is almost equal to that of solving a linear regression problem locally. In such case, the client has no necessary to outsource the computations to the cloud. In scheme 2, it masks a matrix by multiplying two diagonal matrixes. The linear transformation is very vulnerable to statistical attack.