A source authentication method and apparatus according to the present invention are disclosed. The source authentication method is performed with respect to a transmission packet on a message transmission side, and includes generating a first hash value to which a first hash function is applied using a message to be included in a next packet and a key value, and generating the transmission packet including the first hash value, wherein the key value is one of at least one key value generated in advance by applying a second hash function. Meanwhile, according to the present invention, effective low-cost multicast authentication may be performed by reducing a variety of loads such as buffer management, key calculation costs, and the like.