A method, a Network Node and a machine is provided, wherein the machine initially is not provided with an identity which is valid for communication with the communication network. According to the method, the network receives an Activation Request (140, 352, 452, 552, 652) from a User Equipment (320, 420, 520, 620), which User Equipment has an identity which is valid in the communication network and which User Equipment is authenticated in the communication network, the Activation Request comprising a machine identity for the machine. An identity which is valid in said communication network for said machine is obtained (160, 354, 454, 555, 655) on the basis of the Activation Request being received from a User Equipment having a valid identity and being authenticated in the communication network. The obtained identity is transmitted (170, 360, 461, 564, 662) to the machine for enabling the machine to subsequently authenticate itself in one or more communication networks using the obtained identity.