An information processing system performing highly secure broadcast authentication while reducing a delay until authentication, a communication amount, and a computation amount is provided. A server (100) generates authentication information for transmission data by combining a tag relating to the transmission data and a chain value associated in a chain with transmission order of the transmission data. The tag relating to the transmission data is generated by using a common key. The chain is generated by using a one-way function. A node (200) verifies whether a chain value associated with transmission order of data received in the past is generated or not by applying the one-way function to a chain value extracted by using a tag relating to the received data and authentication information for the received data. The tag relating to the received data is generated by using the common key.