When one-time signatures are used for stream authentication, one of the most serious drawbacks is that their large signature size yields high communication overhead. In this paper, we present two efficient one-time signature schemes for stream authentication. Compared with the previous schemes, these schemes have the smallest signature sizes. Moreover, their verification overheads are low. The signature size of Scheme 1 is smaller than that of Scheme 2 whereas Scheme 2 has much smaller signing cost: it requires only 2 hash operations in the majority of cases. Although Scheme 1’s signing cost is relatively high, it can be parallelized without any additional risk because sharing the private key among distributed servers is not required.