A mobile device comprising: a memory; a sensor; and a first processor configured to cause the apparatus to: receive a random challenge c from an online service; read sensor data obtained by sensor or sensors, wherein the sensor data is associated with an application of the device and comprises data on location or position of the device; create a sensor data signature from the sensor data and the random challenge using a private part of an application specific key pair; and send the sensor data signature, the random challenge and the sensor data to the online service, wherein the first processor is further configured to cause the device, prior to receiving the random challenge, to: receive a random nonce n from the online service; select by the application a property to be attested; check if an identity of the application matches the property and if there is a match; create a property signature from the random nonce, the property and a public key of the application specific key pair using a device specific signing key certified with a device specific certificate; and send the property signature to the online service together with the random nonce, the property, the public key and the device specific certificate. a memory; a sensor; and a first processor configured to cause the apparatus to: receive a random challenge c from an online service; read sensor data obtained by sensor or sensors, wherein the sensor data is associated with an application of the device and comprises data on location or position of the device; create a sensor data signature from the sensor data and the random challenge using a private part of an application specific key pair; and send the sensor data signature, the random challenge and the sensor data to the online service, receive a random challenge c from an online service; read sensor data obtained by sensor or sensors, wherein the sensor data is associated with an application of the device and comprises data on location or position of the device; create a sensor data signature from the sensor data and the random challenge using a private part of an application specific key pair; and send the sensor data signature, the random challenge and the sensor data to the online service, wherein the first processor is further configured to cause the device, prior to receiving the random challenge, to: receive a random nonce n from the online service; select by the application a property to be attested; check if an identity of the application matches the property and if there is a match; create a property signature from the random nonce, the property and a public key of the application specific key pair using a device specific signing key certified with a device specific certificate; and send the property signature to the online service together with the random nonce, the property, the public key and the device specific certificate. receive a random nonce n from the online service; select by the application a property to be attested; check if an identity of the application matches the property and if there is a match; create a property signature from the random nonce, the property and a public key of the application specific key pair using a device specific signing key certified with a device specific certificate; and send the property signature to the online service together with the random nonce, the property, the public key and the device specific certificate.