1. A method, comprising: detecting, by a system comprising a processor, a set of contact points corresponding to at least a thumb, an index finger and a middle finger of a hand on a multi-touch device, wherein the hand is associated with a user identity of a set of user identities; determining, by the system, whether the hand is a left hand or a right hand based on a set of finger spanning angles comprising a sum of any two angles between three lines connecting at least a first contact point of the set of contact points, a second contact point of the set of contact points, and a third contact point of the set of contact points to a reference point, wherein the first contact point corresponds to the index finger, the second contact point corresponds to the middle finger, and the third contact point corresponds to the thumb; comparing, by the system, the set of finger spanning angles to a set of registration profile data representing respective finger spanning angles of the set of user identities; and identifying, by the system, the user identity based on a result of the comparing of the set of finger spanning angles to the registration profile data.