As multicast applications are deployed for mainstream use, the need to secure multicast communications will become critical. Multicast, however, does not fit the point-to-point model of most network security protocols which were designed with unicast communications in mind. As we will show, securing multicast (or group) communications is fundamentally different from securing unicast (or paired) communications. In turn, these differences can result in scalability problems for many typical applications. In this paper, we examine and model the differences between unicast and multicast security and then propose Iolus: a novel framework for scalable secure multicasting. Protocols based on Iolus can be used to achieve a variety of security objectives and may be used either to directly secure multicast communications or to provide a separate group key management service to other "security-aware" applications. We describe the architecture and operation of Iolus in detail and also describe our ...

In this paper, we address the question of providing security proofs for signature schemes in the so-called random oracle model [1]. In particular, we establish the generality of this technique against adaptively chosen message attacks. Our main application achieves such a security proof for a slight variant of the El Gamal signature scheme [3] where committed values are hashed together with the message. This is a rather surprising result since the original El Gamal is, as RSA [11], subject to existential forgery.

Given an arbitrary k-bit to k-bit trapdoor permutation f and a hash function, we exhibit an encryption scheme for which (i) any string x of length slightly less than k bits can be encrypted as f(rx), where rx is a simple probabilistic encoding of x depending on the hash function; and (ii) the scheme can be proven semantically secure assuming the hash function is \ideal. " Moreover, a slightly enhanced scheme is shown to have the property that the adversary can create ciphertexts only of strings for which she \knows " the corresponding plaintexts|such ascheme is not only semantically secure but also non-malleable and secure against chosen-ciphertext attack.

The Cipher Block Chaining -- Message Authentication Code (CBC MAC) specifies that a message x = x 1 \Delta \Delta \Delta xm be authenticated among parties who share a secret key a by tagging x with a prefix of f (m) a (x) def = f a (f a (\Delta \Delta \Delta f a (f a (x 1 )\Phix 2 )\Phi \Delta \Delta \Delta \Phix m\Gamma1 )\Phix m ) ; where f is some underlying block cipher (eg. f = DES). This method is a pervasively used international and U.S. standard. We provide its first formal justification, showing the following general lemma: that cipher block chaining a pseudorandom function gives a pseudorandom function. Underlying our results is a technical lemma of independent interest, bounding the success probability of a computationally unbounded adversary in distinguishing between a random ml-bit to l-bit function and the CBC MAC of a random l-bit to l-bit function. Advanced Networking Laboratory, IBM T.J. Watson Research Center, PO Box 704, Yorktown Heights, NY 10598, USA. e-m...

The views and conclusions in this document are those of the authors and do not necessarily represent the official policies or endorsements of any of the research sponsors. How do we build distributed systems that are secure? Cryptographic techniques can be used to secure the communications between physically separated systems, but this is not enough: we must be able to guarantee the privacy of the cryptographic keys and the integrity of the cryptographic functions, in addition to the integrity of the security kernel and access control databases we have on the machines. Physical security is a central assumption upon which secure distributed systems are built; without this foundation even the best cryptosystem or the most secure kernel will crumble. In this thesis, I address the distributed security problem by proposing the addition of a small, physically secure hardware module, a secure coprocessor, to standard workstations and PCs. My central axiom is that secure coprocessors are able to maintain the privacy of the data they process. This thesis attacks the distributed security problem from multiple sides. First, I analyze the security properties of existing system components, both at the hardware and

The design of the IP protocol makes it difficult to reliably identify the originator of an IP packet. Even in the absence of any deliberate attempt to disguise a packet's origin, wide-spread packet forwarding techniques such as NAT and encapsulation may obscure the packet's true source. Techniques have been developed to determine the source of large packet flows, but, to date, no system has been presented to track individual packets in an efficient, scalable fashion. We present a hash-based technique for IP traceback that generates audit trails for traffic within the network, and can trace the origin of a single IP packet delivered by the network in the recent past. We demonstrate that the system is effective, space-efficient (requiring approximately 0.5% of the link capacity per unit time in storage) , and implementable in current or next-generation routing hardware. We present both analytic and simulation results showing the system's effectiveness.

IP version 6 #IPv6# is being designed within the IETF as a replacement for the currentversion of the IP protocol used in the Internet #IPv4#. Wehave designed protocol enhancements for IPv6, known as Mobile IPv6, that allow transparent routing of IPv6 packets to mobile nodes, taking advantage of the opportunities made possible by the design of a new version of IP.InMobile IPv6, each mobile node is always identi#ed by its home address, regardless of its current point of attachment to the Internet. While away from its home IP subnet, a mobile node is also associated with a careof address, which indicates the mobile node's current location. Mobile IPv6 enables any IPv6 node to learn and cache the care-of address associated with a mobile node's home address, and then to send packets destined for the mobile node directly to it at this care-of address using an IPv6 Routing header.

Abstract—This paper presents a detailed analysis of traces of domain name system (DNS) and associated TCP traffic collected

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The development and deployment of practical Semantic Web applications requires technologies for the storage and retrieval of RDF data that are robust and scalable. In this paper, we describe the 3store RDF storage and query engine developed within the Advanced Knowledge Technologies project, and discuss the design rationale and optimisations behind it which enable the efficient handling of large RDF knowledge bases.