Date Added: Jun 2012
Authentication codes (A-codes) are a well studied technique to provide unconditionally secure authentication. An A-code is defined by a map that associates a pair formed by a message and a key to a tag. A-codes linear in the keys have been studied for application to distributed authentication schemes. In this paper, the authors address the dual question, namely the study of A-codes that are linear in the messages. This is usually an undesired property, except in the context of network coding.