DIGITAL AUTHENTICATION “FRIEND-OR-FOE”

Abstract

Based on a modified one-time Winternitz signature scheme, we develop a multi-time two-round group authentication protocol of the type “friend-or-foe.” The main construction is as follows. At each authentication session, members of a group sign only designated w-blocks of a random message. The verifier checks the validity of the whole Winternitz signature. Session public keys are created and sent to the verifier at the previous session. This way, they form a hash-connected blockchain. Security of the Winternitz signature and blockchain structure of public keys imply the security of the suggested protocol. A trusted third party is needed for establishing first “genesis” keys. Also, the protocol has the property “honest verifier zero knowledge”. Keywords: authentication, coalition group, digital signature, the Winternitz signature, blockchain.