Designated group credentials
Consider a situation where a secret agent wants to authenticate herself to the other secret agents. This secret agent must be able to convince the others of her identity. She cannot convince any other people other than those predetermined secret agents. This is to avoid problems that might occur if this secret agent would like to ‘betray’ her group. On the whole we would like to allow the agent to convince a predetermined group of people by showing that she holds a credential and so she is a member of the group. However we would like to prohibit this agent from convincing any other people outside the group. We also need to ensure that the party who has been convinced by the credential cannot use this information to convince any third party. We call this type of scheme as Designated Group Credential. In this paper, we first show a model of designated group credential systems followed by an efficient construction based on pairing-based cryptography. We also provide security proof of our scheme based on the random oracle model.