In current ATM, networks the security issues are gaining a broad attention. For a higher customer satisfaction, the service providers must guarantee the security of the user data. Unless the existing proposals, the method proposed here realizes both the security and integrity services in the ATM layer, so it allows data integrity check in the intermediate network components, too. All the information needed for data integrity is carried in special ATM cells, inserted in the user data flow. At the same time, these special cells make the renegotiation of security service parameters possible. Our model was validated through simulations.