Juan Antonio López-Ramos

A suite of algorithms for key distribution and authentication in centralized secure multicast environments

The Extended Euclidean algorithm provides a fast solution to the problem of finding the greatest common divisor of two numbers. In this paper, we present three applications of the algorithm to the security and privacy field. The first one allows one to privately distribute a secret to a set of recipients with only one multicast communication. It can be used for rekeying purposes in a Secure Multicast scenario. The second one is an authentication mechanism to be used in environments in which a public-key infrastructure is not available. Finally, the third application of the Extended Euclidean algorithm is a zero-knowledge proof that reduces the number of messages between the two parts involved, with the aid of a central server.

Key Management Schemes for Peer-to-Peer Multimedia Streaming Overlay Networks

Key distribution for multimedia live streaming peer-to-peer overlay networks is a field still in its childhood stage. A scheme designed for networks of this kind must seek security and efficiency while keeping in mind the following restrictions: limited bandwidth, continuous playing, great audience size and clients churn. This paper introduces two novel schemes that allow a trade-off between security and efficiency by allowing to dynamically vary the number of levels used in the key hierarchy. These changes are motivated by great variations in audience size, and initiated by decision of the Key Server. Additionally, a comparative study of both is presented, focusing on security and audience size. Results show that larger key hierarchies can supply bigger audiences, but offer less security against statistical attacks. The opposite happens for shorter key hierarchies.

Managing key multicasting through orthogonal systems

Abstract In this paper we propose a new protocol for Group Key Management. The protocol is based on the use of orthogonal systems in vector spaces. The main advantage in comparison to other existing multicast key management protocols consists in small communications overheads, i.e. length and number of messages to be sent, as well as key storage, especially with respect to a comparable security level. This makes the protocol especially attractive when the number of legitimate receivers is large.

Group Oriented Renewal of Secrets and Its Application to Secure Multicast

This paper introduces a multicast method for renewing secrets which are shared by a set of hosts. The method is centralized, secure, efficient, scalable to a reasonable size and compatible with any multicast topology configuration underneath. It can be used to achieve privacy in a centralized multicast overlay. Additionally, the method can be used to renew an asymmetric key pair when a cryptosystem based on discrete logarithm is used. Knowledge of the public key is then restricted to the group it is communicated to. Security and scalability are discussed, and a comparison with other well-known alternatives is shown.

Group key management based on semigroup actions

In this work we provide a suite of protocols for group key management based on general semigroup actions. Construction of the key is made in a distributed and collaborative way. Examples are provided that may in some cases enhance the security level and communication overheads of previous existing protocols. Security against passive attacks is considered and depends on the hardness of the semigroup action problem in any particular scenario.

Hardware implementation of a new ECC key distribution protocol for securing Wireless Sensor Networks

Security in Wireless Sensor Networks (WSNs) is a major challenge for extending its applications. In this paper, a new protocol for key distribution in WSNs is proposed. The method, based on Elliptic Curve Cryptography, and named ECGDH-1, performs a double round key distribution, sharing a group key among the different nodes. For accelerating the scalar-point operations to be performed in each node, a hardware coprocessor with low power consumption, and 8-bit interface for sensor motes is proposed. The cryptographic processor, named ECCB163sens_bus8 allows completing a scalar-point multiplication in 240us operating at 8MHz, while consuming only 0.028mJ by operation when implemented in a Spartan 6 device.

Determining all indecomposable codes over some Hopf algebras

We determine all indecomposable codes over a class of Hopf algebras named Taft Algebras. We calculate dual codes and tensor products of these indecomposable codes and give applications of them.

An active attack on a distributed Group Key Exchange system

In this work, we introduce an active attack on a Group Key Exchange protocol by Burmester and Desmedt. The attacker obtains a copy of the shared key, which is created in a collaborative manner with the legal users in a communication group.

A decentralized protocol for mobile control access

In this paper we use the Diffie–Hellman key exchange protocol to introduce a decentralized key agreement protocol based on elliptic curves. We do not use any public key infrastructure, which makes it suitable for light devices with low computational and storage capabilities. Thus mobile devices can directly authorize other mobile devices to exchange keys in order to get access to a service or system, in a secure and efficient manner.

A scalable server for key distribution and its application to accounting

Media distribution over the Internet is a fact. Finding a way to protect content streaming is a hot topic. This paper presents both a new and efficient key multicasting protocol based on the use of orthogonal systems in vector spaces, and its scalable implementation by means of a platform independent server. The protocol outstands in exchanging a small number of tiny messages which helps the server to scale when facing a huge number of legitimate users.