Source authentication method for secure multicast

The invention relates to a source authentication method for secure multicast. The source authentication method comprises the following steps: an authentication center distributes a private key which can represent the identity only to members of a multicast group; a sending end obtains a message abstract by hash function processing of image information to be sent, obtains a digital signature by using the private key to encrypt the message abstract, carries out DCT (Discrete Cosine Transform) on carrier images, and embeds the digital signature into an intermediate-frequency coefficient part as a digital watermark; after receiving the images, a receiving end extracts watermark information from the intermediate-frequency coefficient part, decrypts the watermark information by adopting a public key so as to judge the identity of a sender, finish identity authentication and obtain the information abstract simultaneously, then adopts the same hash function to process the images without the watermark information, and obtains two message abstracts; and if the two message abstracts are same, no occurrence of content tampering can be judged, or, the occurrence of content tampering is judged, and further the acceptance and rejection of the received images are decided.