In the next coming years, many of our basic activities such as reading an e-mail, checking our bank account, buying on-line, etc., will be performed by using a smartphone in a mobile environment. It is quite obvious that the degree of security granted by a classic username-password access is not sufficient and that a stronger level of safeness is required. However, usually adopted additional instruments such as smart cards, USB sticks and OTP generators are not always available or usable in mobility. In this paper a possible solution which envisages the use of the user's own smartphone as a mean to grant a safer and easy mobile access is presented. The objective is to introduce a novel methodology to obtain a robust smartphone fingerprint by opportunely combining different intrinsic characteristics of each sensor. Modern mobile phones, in fact, have several kinds of sensors such as accelerometer, gyroscope, magnetometer, microphone and camera; such sensors can be used to uniquely identify each phone by measuring the specific anomalies left onto the signals they acquire. Satisfactory results have been obtained when the sensors are used in combination, especially accelerometer and digital camera, achieving a significant level of smartphone distinctiveness.