Multisignature Protocols and Problem of Simultaneous Signing a Package of Contracts

Electronic messages authentication is an issue of significant importance for geographical information systems (GIS). In some cases the multisignature protocols can be effectively applied to solve efficiently special information authentication problems in GIS. New multisignature protocols based on the discrete logarithm problem in finite groups are introduced. The protocols are based on digital signature schemes over multiplicative groups of the ground finite fields, elliptic curves (EC), and vector groups, the last being a new cryptographic primitive. The protocols provide generation of the collective digital signature (DS) possessing internal integrity. Nobody participating in the protocol is able to form a valid collective DS that corresponds to reduced number of the signers. Besides, the collective DS of some special type can prove that a package of documents is signed by different sets of signers, and moreover the collective DS is formed simultaneously by all signers. Therefore the protocols solve the well-known problem of simultaneous signing a contract as well as they solve the more difficult problem of simultaneous signing a package of contracts. The paper considers applicability of the known DS standards to implement the proposed protocols.