1. A method of verifying an input signature made, the method comprising: receiving a touch event and a proximity touch event that occur on a touch input unit of an apparatus; extracting features of the input signature, the features including a touch feature associated with the touch event, and a proximity touch feature associated with the proximity touch event; and determining whether to authenticate the input signature based on a first similarity between the touch feature of the input signature and a corresponding touch feature of a previously stored reference signature, and a second similarity between the proximity touch feature and a corresponding proximity touch feature of the previously stored reference signature, wherein the second similarity is given more weight than the first similarity in determining whether to authenticate the input signature.