1. An apparatus comprising: a central processing unit configured to control at least one of: a determining unit configured to analyze signature data corresponding to a handwritten signature, and determine whether to register the signature based on a characteristic of the signature; and a notifying unit configured to provide information relating to making the signature registerable according to a writing style of the signature, if it is determined by the determining unit not to register the signature, wherein the determining unit determines whether to register the signature using as a determination criterion at least one of cumulative angle changes in a locus of the signature, fluctuation in a writing speed of the signature, fluctuation in a size of each character included in the signature, and fluctuation in a center position of each character included in the signature.