Abstract: The session key S is divided into a sum of S1 and S2. Under the condition of large integer factoring problem, S1 is decrypted by constructing a special polynomial function （scheme 1 ）. Under the condition of discrete logarithm problem, S2 is decrypted by

Key words: Collusion-resistance,Asymmetric, Long-lived subscriber＇s key, Black-box tracing