The present invention relate to a method for authenticating a low performance device, and more particularly, to a device authenticating method, in which a low performance device such as a smart meter of a smart grid is authenticated in a matrix operation instead of an exponential operation through a homomorphic hash function (HHF) of a non-square matrix M, so that the amount of operations required for authenticating the device can be reduced and the device can be safely authenticated even without a separate certificate authority.