Secret Handshake Scheme with Request-Based-Revealing

Secret handshake (

SH

) schemes enable two members who belong to the same group to authenticate each other in a way that hides their affiliation to that group from all others. In previous works, the group authority (GA) has the ability to reveal the identity (ID) of a handshake player who belongs to his group. In this paper, we focus first on the classification of traceability of GA. We classify this feature as follows: (i) GA of

G

is able to reveal IDs of members belonging to

G

by using a transcript of a handshake protocol; (ii) GA of

G

is able to confirm whether handshake players belong to

G

or not by using a transcript of a handshake protocol. In some situations, only the latter capability is needed. So, we consider a

SH

that GA has only an ability to confirm whether a handshake player belongs to his own group without revealing his ID. Thus, we introduce a

SH scheme with request-based-revealing

(

SHRBR

). In

SHRBR

, GA can check whether handshake players belong to the own group without revealing a member ID. After a handshake player

A

executes a handshake protocol with

B

, if

A

wants to reveal a handshake partner (in this case

B

),

A

requests GA to reveal a handshake partner’s ID by bringing forth his own ID and secret information. We define the security requirements for

SHRBR

and propose a concrete

SHRBR

in the random oracle model.