Unconditionally Secure Blind Authentication Codes: The Model, Constructions, and Links to Commitment

Abstract

In this paper, as a fundamental cryptographic protocol with information-theoretic security, we propose an unconditionally secure blind authentication code (BA-code for short) which is an unconditionally secure authentication code with anonymity of messages. As we will see, the BA-code is a simple model of an authentication code with the function similar to that of the unconditionally secure blind signature (USBS for short). The relationship between BA-codes and USBS is similar to the one between traditional authentication codes and unconditionally secure signature schemes as well as the one between group authentication codes and group signature schemes. In addition, we provide two kinds of constructions of BA-codes: direct constructions based on polynomials over finite fields, and a generic construction by using unconditionally secure encryption and A2-codes. Furthermore, as application we show a link between BA-codes and commitment in unconditional security setting: starting from BA-codes, unconditionally secure commitment schemes can be constructed in a black-box way.