Broadcast authentication is a critical security service in wireless sensor networks. A protocol namedμTESLA has been proposed to provide effcient authentication service for such networks. However, when applied to applications such as time synchronization and firealarm in which broadcast messages are sent infrequently,μTESLA encounters problems of wasted key resources andslow message verification. This paper presents a newprotocol named GBA (Generalized broadcast authentication), for effcient broadcast authentication in these applications. GBA utilizes the one-way key chain mechanism ofμTESLA, but modifies the keys and time intervals association, and changes the key disclosure mechanism accordingto the message transmission model in these applications.The proposed technique can take full use of key resources,and shorten the message verification time to an acceptablelevel. The analysis and experiments show that GBA ismore effcient and practical than μTESLA in applicationswith various message transmission models.