Verifying data integrity

It is provided a method for enabling a user device to verify data integrity. The method is performed in a network node and includes: obtaining measurement data indicating resource usage by the user device; obtaining a session identifier; generating a measurement indicator using a one-way function, based on the measurement data; generating an asymmetric cryptographic signature of the session identifier and the measurement indicator, the asymmetric cryptographic signature being based on a private key of a cryptographic key pair of the network node; and storing, in a distributed ledger database, a set of data comprising the asymmetric cryptographic signature, the session identifier and the measurement indicator.