An efficient authentication protocol with low communication latency is crucial to the success of 3G/WLAN interworking for further services. This paper, based on error-correcting codes, one-way hashing function and symmetric key cryptography, proposes a new authentication scheme for integrated 3G/WLAN networks. The new scheme provides better anonymity because it does not expose users' identifiers on the air even they are authenticated for the first time while EAP-AKA will expose users' real identities when they visit new domains. Additionally, it greatly improves the communication performance.