Cryptographic enforcement of information flow policies without public information via tree partitions

We may enforce an information flow policy by encrypting a protected resource and ensuring that only users authorized by the policy are able to decrypt the resource. In most schemes in the literature that use symmetric cryptographic primitives, each user is assigned a single secret and derives decryption keys using this secret and publicly available information. Recent work has challenged this approach by developing schemes, based on a chain partition of the information flow policy, that do not require public information for key derivation, the trade-off being that a user may need to be assigned more than one secret. In general, many different chain partitions exist for the same policy and, until now, it was not known how to compute an appropriate one. In this paper, we introduce the notion of a tree partition, of which chain partitions are a special case. We show how a tree partition may be used to define a cryptographic enforcement scheme and prove that such schemes can be instantiated in such a way as to preserve the strongest security properties known for cryptographic enforcement schemes. We establish a number of results linking the amount of secret material that needs to be distributed to users with a weighted acyclic graph derived from the tree partition. These results enable us to develop efficient algorithms for deriving tree and chain partitions that minimize the amount of secret material that needs to be distributed.Comment: Extended version of conference papers from ACNS 2015 and DBSec 201

Using secure coprocessors to enforce network access policies in enterprise and ad hoc networks

Nowadays, network security is critically important. Enterprises rely on networks to improvetheir business. However, network security breaches may cause them loss of millions of dollars.Ad hoc networks, which enable computers to communicate wirelessly without the need forinfrastructure support, have been attracting more and more interests. However, they cannotbe deployed effectively due to security concerns.Studies have shown that the major network security threat is insiders (malicious orcompromised nodes). Enterprises have traditionally employed network security solutions(e.g., firewalls, intrusion detection systems, anti-virus software) and network access controltechnologies (e.g., 802.1x, IPsec/IKE) to protect their networks. However, these approachesdo not prevent malicious or compromised nodes from accessing the network. Many attacksagainst ad hoc networks, including routing, forwarding, and leader-election attacks, requiremalicious nodes joining the attacked network too.This dissertation presents a novel solution to protect both enterprise and ad hoc networksby addressing the above problem. It is a hardware-based solution that protects a networkthrough the attesting of a node's configuration before authorizing the node's access to thenetwork. Attestation is the unforgeable disclosure of a node's configuration to another node,signed by a secure coprocessor known as a Trusted Platform Module (TPM).This dissertation makes following contributions. First, several techniques at operatingsystem level (i.e., TCB prelogging, secure association root tripping, and sealing-free attestation confinement) are developed to support attestation and policy enforcement. Second, two secure attestation protocols at network level (i.e., Bound Keyed Attestation (BKA) andBatched Bound Keyed Attestation (BBKA)) are designed to overcome the risk of a man-inthe-middle (MITM) attack. Third, the above techniques are applied in enterprise networks todifferent network access control technologies to enhance enterprise network security. Fourth,AdHocSec, a novel network security solution for ad hoc networks, is proposed and evaluated. AdHocSec inserts a security layer between the network and data link layer of the networkstack. Several algorithms are designed to facilitate node's attestation in ad hoc networks,including distributed attestation (DA), and attested merger (AM) algorithm

03411 Abstracts Collection -- Language Based Security

From October 5th to 10th 2003,the Dagstuhl Seminar 03411 ``Language Based security\u27\u27 was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar are put together in this paper