The OLYMPUS Architecturexe2x80x94Oblivious Identity Management for Private UserFriendly Services Privacy enhancing technologies (PETs) allow to achieve userxe2x80x99s transactions unlinkability across different online Service Providers. However, current PETs fail to guarantee unlinkability against the Identity Provider (IdP), which becomes a single point of failure in terms of privacy and security, and therefore, might impersonate its users. To address this issue, OLYMPUS EU project establishes an interoperable framework of technologies for a distributed privacypreserving identity management based on cryptographic techniques that can be applied both to online and offline scenarios. Namely, distributed cryptographic techniques based on threshold cryptography are used to split up the role of the Identity Provider (IdP) into several authorities so that a single entity is not able to impersonate or track its users. The architecture leverages PET technologies, such as distributed thresholdbased signatures and privacy attributebased credentials (pABC), so that the signed tokens and the ABC credentials are managed in a distributed way by several IdPs. This paper describes the Olympus architecture, including its associated requirements, the main building blocks and processes, as well as the associated use cases. In addition, the paper shows how the Olympus oblivious architecture can be used to achieve privacypreserving M2M offline transactions between IoT devices.

Intersectionpolicy private mutual authentication from authorized private set intersection Private mutual authentication (PMA) enables twoway anonymous authentication between two users certified by the same trusted group authority. Most existing PMA schemes focus on acquiring a relatively onefold authentication policy that ensures affiliationhiding or designated singleattribute matching. However, in practice, users are typically provided with multiple attributes. In addition to the affiliationhiding requirement, how to effectively achieve a more flexible authentication policy for multiattribute applications remains a challenging issue. The intersection policy for authentication is also required when the attribute intersection is not an empty set or its cardinality is no less than a threshold value. To solve the above problems, we first propose an optimal authorized private set intersection protocol with forward security based on identitybased encryption and then design a new PMA protocol with intersectionpolicy called IPPMA, which provides a simple solution for secret handshakes between two members (holding multiple attributes) from the same organization. Formal security analyses proved that our two proposed protocols are secure in the random oracle model. Empirical tests demonstrated that the IPPMA protocol is optimized with linear complexity and may be more suitable for resourceconstrained applications.