A computing apparatus configured to verify a digital signature applied on a set of data received from a user device, including an user ID assigned by a partner system to uniquely identify a user of the user device among customers of the partner system, and a user device identifier identifying the user device. The digital signature is generated via applying a cryptographic one-way hash function on a combination of the set of data and a secret, shared between the computing apparatus and the partner system via a secure communication channel separate from a channel used to receive the set of data.