We consider the stream authentication problem when an adversary has the ability to drop, reorder or inject data packets in the network. We propose a coding approach for multicast stream authentication using the list-decoding property of Reed-Solomon codes. We divide the data to be authenticated into a stream of packets and associate a single signature for every λ n packets where λ and n are predesignated parameters. Our scheme, which is also joinable at the boundary of any n-packet block, can be viewed as an extension of Lysyanskaya, Tamassia and Triandopoulos's technique in which λ = 1. We show that by choosing λ and n appropriately, our scheme outperforms theirs in both signature and verification time. Our approach relies on signature dispersion as SAIDA and eSAIDA. Assuming that we use RSA for signing and MD5 for hashing, we give an approximation of the proportion of extra packets per block which could be processed via our technique with respect to the previous scheme. As example when we process λ = 1000 blocks of 20000 64-byte-packets, the gain of our scheme with respect to Lysyanskaya et al.'s is about 30%.