A ring authentication method for a concurrency environment, the method capable of providing unforgeability, sender anonymity, and deniability in the concurrency environment, in which, when a receiver receiving a message requests a sender of the message to certify the message, the sender requested to certify the message sends a message certification value certifying that the sender is one of a plurality of users {P1, . . . , Pn} and authenticates the message m to the receiver, and the receiver verifies the sent message certification value and authenticates that the message is sent from the one of the plurality of users {P1, . . . , Pn}.