In this paper, a new digital true random number generator based on Cross Feedback Ring Oscillators (CFRO) is proposed. The random sources of CFRO lie in delay variations (jitter), unpredictable transition behaviors as well as metastability. The CFRO is proved to be truly random by restarting from the same initial states. Compared with the so-called Fibonacci Ring Oscillator (FIRO) and Galois Ring Oscillator (GARO), the CFRO needs less than half of their time to accumulate relatively high entropy and enable extraction of one random bit. Only a simple XOR corrector is used to reduce the bias of output sequences. TRNG based on CFRO can be run continuously at a constant high speed of 150Mbps. For higher security, the TRNG can be set in stateless mode at a cost of slower speed of 10Mbps. The total logical resources used are relatively small and no special placement and routing is needed. The TRNG both in continuous mode and in stateless mode can pass the NIST tests and the DIEHARD tests.

Source routing multicast has been gathering much more attention rather than traditional IP multicast, since it is thought to be more scalable in terms of the number of groups at the cost of higher traffic loads. This paper introduces a mathematical framework to analyze the scalability of source routing multicast and IP multicast by leveraging previous multicast studies. We first analyze the amount of data traffic based on the small-world nature of networks, and show that source routing multicast can be as efficient as IP multicast if a simple header fragmentation technique (subgrouping) is utilized. We also analyze scalability in terms of group numbers, which are derived under the equal budget assumption. Our analysis shows that source routing multicast is competitive for low bit-rate streams, like those in the publish/subscribe service, but we find some factors that offset the advantage. This is the first work to analytically investigate the scalability of source routing multicast.

Scalability is one of the most important requirements for secure multicast in a multi-group environment. In this study, we propose a decentralized multi-group key management scheme that allows each multicast group sender to control the access to its group communication independently. Scalability is enhanced by local rekeying and inter-working among different subgroups. The group key secrecy and backward/forward secrecy are also guaranteed.

Broadcast encryption technology enables a sender to send information securely to a group of receivers excluding specified receivers over a broadcast channel. In this paper, we propose a new key-tree structure based on Rabin cryptosystem, and an access control scheme using the structure. We show the security of the access control scheme and construct a new broadcast encryption scheme based on it. The proposed broadcast encryption scheme is a modification of the complete subtree method and it reduces the number of keys a receiver stores to one. There have been proposed some modifications of the complete subtree method which minimize the number of keys for a receiver to one, and the most efficient one among them with respect to the computational overhead at receivers is based on RSA cryptosystem. The computational overhead at receivers in our scheme is around log2e times smaller than the most efficient previously proposed one, where e is a public exponent of RSA, and the proposed scheme is the most efficient among tree based one-key schemes. This property is examined by experimental results. Our scheme achieves this reduction in the computational overhead in exchange for an increase in the size of nonsecret memory by [log n * few (e.g. eight)] bits, where n is the total number of receivers.

In this paper, we propose a multicast protocol, called BAM (Branch Aggregation Multicast), for wireless sensor networks. The main contribution of BAM is a reduction in the radio communication load, which is a key determinant of sensor energy consumption. BAM does not use any control packets such as join/leave messages and does not manage multicast groups. BAM is highly compatible with existing wireless sensor protocols, such as routing protocols, MAC protocols, and other kinds of energy efficient protocols. BAM implementation is quite simple and BAM works on various networks even if some sensors are not BAM-capable. BAM is composed of two aggregation techniques. One is single hop aggregation (S-BAM) and the other is multiple paths aggregation (M-BAM). S-BAM aggregates radio transmission within a single hop and enables single transmission to multiple intended receivers. M-BAM aggregates multiple paths into fewer ones and limits the range of radio transmission. S-BAM is designed to reduce redundant communication at every branch while M-BAM is designed to reduce the number of branches. SM-BAM, the combination of S-BAM and M-BAM, can reduce the radio communication load thus enabling energy efficient multicast communication. We evaluate BAM in three ways, qualitative evaluation by theoretical analysis, quantitative evaluation through computer simulations, and experiments using CrossBow's MICA2. Our results show that BAM is a very energy efficient multicast protocol that well supports wireless sensor networks.

The complete subtree (CS) method is widely accepted for the broadcast encryption. A new method for assigning keys in the CS method is proposed in this paper. The essential idea behind the proposed method is to use two trapdoor permutations. Using the trapdoor information, the key management center computes and assigns a key to each terminal so that the terminal can derive all information necessary in the CS method. A terminal has to keep just one key, while log2 N + 1 keys were needed in the original CS method where N is the number of all terminals. The permutations to be used need to satisfy a certain property which is similar to but slightly different from the claw-free property. The needed property, named strongly semi-claw-free property, is formalized in terms of probabilistic polynomial time algorithm, and its relation to the claw-free property is discussed. It is also shown that if the used permutations fulfill the strongly semi-claw-free property, then the proposed method is secure against attacks of malicious users.

This paper deals with broadcast encryption schemes, in which a sender can send information securely to a group of receivers excluding some receivers over a broadcast channel. In this paper we propose modifications of the Complete Subtree (CS), the Subset Difference (SD) and the Layered Subset Difference (LSD) methods based on the Master Key Tree (MKT). Our modifications eliminate log N keys or labels from receivers' storage, in exchange for an increase in the computational overhead, where N is the total number of receivers. We also propose modifications of the SD and LSD methods by applying the Trapdoor One-way Permutation Tree (TOPT) which is originally proposed in order to modify the CS method. Our modifications based on TOPT also eliminate log N labels, and the computational cost is much smaller than MKT based methods.

The complete subtree (CS) method is one of the most well-known broadcast encryptions which do not enforce the receivers to keep "online." This paper is to reduce the size of secret information which must be stored in a terminal of the method. In the original CS method, the size of the secret information increases as the number of terminals increases. It is shown in this paper that, by making use of a one-way trapdoor permutation, we can make the size constant regardless of the number of terminals. The security of the proposed scheme is investigated, and detailed comparison with other similar schemes is presented. The proposed scheme is suitable for practical implementations of the CS method.

Service differentiation has been a subject of research for the past few years in the IETF; and in the current Internet, IP flows are mostly treated in a best-effort approach. However, for next generation networks it is expected that users would like to obtain service differentiation based on their preferences or profiles as well as the different types of multimedia they opt to receive or send. In addition, current Quality of Service (QoS) provisioning architectures have been designed mostly for the fixed networks without taking into consideration the wireless or radio links special requirements, such as low bandwidth availability, error prone communications, etc. In this paper we propose a QoS provisioning architecture for next generation networks that uses a hybrid approach to deal with both the wireless and wired (fixed) part of the network. For administering the scarce resource of the radio environment, we have developed a resource allocation algorithm based on micro-economic principles that uses associated piecewise linear utility functions which describe the benefit a user receives from the allocation of various amounts of resource. For the wired part of the network we have also developed a Core-Stateless Utility based Rate allocation Framework (SURF) for performing traffic policing where the flow's requirements are expressed using utility functions. The core routers maintain no per-flow state and implement a simple packet level admission control algorithm that is based on a threshold utility value that is computed dynamically. To tie in these two mechanisms, we developed a signaling mechanism that collect network statistics when a user starts a call and a QoS administrator entity (or Broker) perform the computations for allocating resources based on the information of available resources in the fixed and the wireless sections of the network. A comparison between the hybrid approach and the SURF approach to show the performance of the proposed architecture is presented later in the paper.

The differentiated services (diffserv) architecture has been proposed for implementing scalable service differentiation in the Internet. Expedited forwarding and assured forwarding have been standardized as Per-Hop Behaviors (PHB) in diffserv. Assured forwarding can be utilized to realize the service, which provides each user with a minimum guaranteed rate and a fair share of the residual bandwidth. We call it guaranteed rate (GR) service. With GR service, each packet for flow i is marked in or out based on comparison between the sending rate and the minimum guaranteed rate. When congestion occurs in networks, out packets are dropped more aggressively than in packets. Recently, several fair queuing schemes have been proposed for core stateless networks. They can achieve fairer bandwidth allocation than random early detection (RED). However, there have not been any studies that consider in/out bit usage to support GR service. This paper proposes how to extend the schemes that have been proposed for core stateless networks to allow the support of in/out bit usage. We present the performance of one of the extended schemes and compare the scheme to RED with in/out bit (RIO) in terms of fair bandwidth allocation.