A Tree-based Model of Unicast Stream Authentication

When proving the security of a message authentication scheme, the messages are considered to be atomic objects. Straightforward application of such schemes to some information resources may introduce security flaws. Gennaro and Rohatgi (Crypto ’97) identified the streams of data as an important class of information resources that can not be considered to be message-like, and they proposed a solution to the problem of stream signing when the stream is not known in advance. The disadvantage of digital signing streams of data is that it is not efficient when nonrepudiation is not important, as in the case of point-to-point communications. We present several schemes and also a family of schemes for stream authentication in a unicast setting. Since many authentication schemes have been broken, we will prove our solutions.