UMTS provides a high mobility two-way multimedia service with a medium bit rate. DVB provides high bit rate mobile reception, but restricted to a unidirectional one-to-one. The convergence of telecommunication and broadcasting networks have problem about how to support mutual authentication between user and broadcasting network. In this paper, we propose a new authentication scheme that authenticates each other. We involve UMTS AKA to share session key between user and converged networks. The AKA is based on symmetric keys, and runs typically in a UMTS subscriber identity mobile, a smart card like device. AKA mechanism is based on a challenge and response authentication protocol conceived in such a way as to achieve maximum compatibility with UMTS subscriber authentication and key establishment protocol.The VLR/SGSN checks user identity such as IMSI with PSI/SI which is transmitted through interface Ii. If the UMTS authentication user corrects PSI/SI table, DVB-H network transmits data with unnecessary authentication. The session key is used in every session to encapsulate the data sent to the user. Our proposed authentication scheme provide a fast and secure authentication for the converged networks.