Abstract
Liaw proposed a secure broadcasting scheme which requires fewer broadcasting messages than other existing schemes. In order to provide security, the operation of Liaw's broadcasting cryptosystem becomes infeasible, because a very large amount of information must be kept by each user, and be sent for each broadcast. Also, the running time for deriving an encryption key is exponentially large because no modulus operation can be applied to reduce the size of the exponents in Liaw's scheme.