There is disclosed a system for authentication of a device in a network by establishing a second security context between the device and a serving network node when a first security context has previously been established, assisted by an authentication server, based on a random value and a secret shared between an identity module associated with the device and the authentication server. First re-use information from the establishment of the first security context is stored at the authentication server and at the device, the first re-use information enabling secure generation of the second security context from the random value and the secret. Second re-use information may be generated or stored at the device. A context regeneration request is generated at the device, the context regeneration request authenticated at least partly based on the secret. The context regeneration request is sent to the serving network node. The context regeneration request is sent from the serving network node to the authentication server. The context regeneration request is verified at the authentication server. The second security context is generated at the authentication server based on at least the secret, the random value, and the first and second re-use information. The second security context is communicated from the authentication server to the serving network node.