Efficient and Unconditionally Secure Digital Signatures and a Security Analysis of a Multireceiver Authentication Code

Digital signatures whose security does not rely on any unproven computational assumption have recently received considerable attention. While these unconditionally secure digital signatures provide a foundation for long term integrity and non-repudiation of data, currently known schemes generally require a far greater amount of memory space for the storage of users’ secret information than a traditional digital signature. The focus of this paper is on methods for reducing memory requirements of unconditionally secure digital signatures. A major contribution of this paper is to propose two novel unconditionally secure digital signature schemes that have significantly shortened secret information for users. As a specific example, with a typical parameter setting the required memory size for a user is reduced to approximately 1 10 of that in previously known schemes. Another contribution of the paper is to demonstrate an attack on a multireceiver authentication code proposed by Safavi-Naini and Wang, and present a method to fix the problem of the code.