Search

The notion of Affiliation-Hiding Authenticated Group Key Agreement (AH-AGKA) protocols was first introduced by Jarecki et al. in CT-RSA 2007, where they presented two concrete AH-AGKA protocols. In this paper, we show that Jarecki et al.'s second protocol has some drawbacks. We propose a new affiliation-hiding protocol. Differing from Jarecki et al.'s protocol, our protocol is asymmetric. Compared with existing AH-AGKA protocols, our scheme not only exhibits the affiliation-hiding property, but also holds the properties of detectability and perfect forward secrecy. [ABSTRACT FROM PUBLISHER]

We introduce the concept of Affiliation-Hiding Authenticated Asymmetric Group Key Agreement (AH-AAGKA) and construct a concrete one-round AH-AAGKA protocol. An AH-AAGKA protocol allows the participants of a group to establish a common encryption key associated with several decryption keys; each of which can only be computed by the corresponding legitimate group member. An AH-AAGKA protocol has the following privacy feature. For a member i of a group G, if i participates in an AH-AAGKA protocol, any protocol participant j cannot learn whether i is a member of G, unless j himself is a member of group G. Our scheme demonstrates new features in comparison with other existing AH-AGKA protocols. If non-group members participate in our protocol, honest parties can identify these non-group members. Our scheme also captures Unlinkability and Perfect Forward Secrecy (PFS), which are missing in other existing schemes. We propose a novel security model to prove that our protocol holds PFS and present a new privacy model to prove that our scheme meets Affiliation-Hiding property. [ABSTRACT FROM AUTHOR]

Identity (ID) uniqueness is essential in distributed hash table (DHT)-based systems, as peer lookup and resource searching rely on ID matching. However, many DHT implementations in the wild, such as Kad and Mainline, do not enforce such uniqueness. Most previous works and measurements on DHTs do not take into account that IDs among peers may not be unique. Unfortunately, we observe that a significant portion of peers, i.e. 19.5% of the peers in Kad and 4.0% of the peers in Mainline, do not have unique IDs. These repetitions would mislead the measurements and modeling on those networks. We further focus on investigating the repetition in Kad considering its wider usage and more serious situation of repetition. We observe that there are a large number of peers that frequently change their UDP ports, and there are a few IDs that repeat for a large number of times and all peers with these IDs do not respond to Kad protocol. We also analyze the effects of ID repetitions under simplified settings and find that the current repetition degrades Kad's performance on publishing and searching, but has insignificant effect on lookup process. These measurement and analysis are useful to further determine the sources of repetitions and are also useful for finding suitable parameters in publishing and searching processes in DHT networks without compulsive ID uniqueness. [ABSTRACT FROM AUTHOR]