Cryptographic Key Management in Delay Tolerant Networks: A Survey

Since their appearance at the dawn of the second millennium, Delay or Disruption Tolerant Networks (DTNs) have gradually evolved, spurring the development of a variety of methods and protocols for making them more secure and resilient. In this context, perhaps, the most challenging problem to deal with is that of cryptographic key management. To the best of our knowledge, the work at hand is the first to survey the relevant literature and classify the various so far proposed key management approaches in such a restricted and harsh environment. Towards this goal, we have grouped the surveyed key management methods into three major categories depending on whether the particular method copes with (a) security initialization, (b) key establishment, and (c) key revocation. We have attempted to provide a concise but fairly complete evaluation of the proposed up-to-date methods in a generalized way with the aim of offering a central reference point for future research.

Related papers:

title: Automated key exchange protocol evaluation in delay tolerant networks
abstract: Cryptographic key exchange is considered to be a challenging problem in Delay Tolerant Networks (DTNs) operating in deep space environments. The difficulties and challenges are attributed to the peculiarities and constraints of the harsh communication conditions that DTNs typically operate in, rather than the actual features of the underlying key management cryptographic protocols and solutions. In this paper we propose a framework for evaluation of key exchange protocols in a DTN setting. Our contribution is twofold as the proposed framework can be used as a decision making tool for automated evaluation of various communication scenarios with regards to routing decisions and as part of a method for protocol evaluation in DTNs.

title: Bundle Protocol Specification
abstract: This document describes the end-to-end protocol, header formats, and
abstract service description for the exchange of messages (bundles) in
Delay Tolerant Networking (DTN).

title: Identity-Based Cryptosystems and Signature Schemes
abstract: In this paper we introduce a novel type of cryptographic scheme, which enables any pair of users to communicate securely and to verify each other’s signatures without exchanging private or public keys, without keeping key directories, and without using the services of a third party. The scheme assumes the existence of trusted key generation centers, whose sole purpose is to give each user a personalized smart card when he first joins the network. The information embedded in this card enables the user to sign and encrypt the messages he sends and to decrypt and verify the messages he receives in a totally independent way, regardless of the identity of the other party. Previously issued cards do not have to be updated when new users join the network, and the various centers do not have to coordinate their activities or even to keep a user list. The centers can be closed after all the cards are issued, and the network can continue to function in a completely decentralized way for an indefinite period.

title: A Formally Verified Decentralized Key Management Architecture for Wireless Sensor Networks
abstract: We present a decentralized key management architecture for wireless sensor networks, covering the aspects of key deployment, key refreshment and key establishment. Our architecture is based on a clear set of assumptions and guidelines. Balance between security and energy consumption is achieved by partitioning a system into two interoperable security realms: the supervised realm trades off simplicity and resources for higher security whereas in the unsupervised realm the vice versa is true. Key deployment uses minimal key storage while key refreshment is based on the well-studied scheme of Abdalla et al. The keying protocols involved use only symmetric cryptography and have all been verified with our constraint solving-based protocol verification tool CoProVe.

title: Security analysis of DTN architecture and Bundle Protocol Specification for space-based networks
abstract: A Delay-Tolerant Network (DTN) Architecture (Request for Comment, RFC-4838) and Bundle Protocol Specification, RFC-5050, have been proposed for space and terrestrial networks. Additional security specifications have been provided via the Bundle Security Specification (currently a work in progress as an Internet Research Task Force internet-draft) and, for link-layer protocols applicable to Space networks, the Licklider Transport Protocol Security Extensions. This document provides a security analysis of the current DTN RFCs and proposed security related internet drafts with a focus on space-based communication networks, which is a rather restricted subset of DTN networks. Note, the original focus and motivation of DTN work was for the ‘Interplanetary Internet’. This document does not address general store-and-forward network overlays, just the current work being done by the Internet Research Task Force (IRTF) and the Consultative Committee for Space Data Systems (CCSDS) Space Internetworking Services Area (SIS) - DTN working group under the ‘DTN’ and ‘Bundle’ umbrellas. However, much of the analysis is relevant to general store-and-forward overlays.

title: Secure and Efficient Key Management Scheme in MANETs
abstract: InMobile ad hoc networks (MANETs) security has become a primary requirements.Thecharacteristics capabilities of MANETsexposeboth challenges and opportunities in achieving key security goals,such as confidentiality,access control,authentication, availability, integrity, and non- repudiation.Cryptographic techniques are widely used for secure communications in both TCP and UDPnetworks. Most cryptographic mechanisms, such as symmetric and asymmetric cryptography,often involve the use of cryptographic keys. However, all cryptographic techniques will beunsecure or inefficient if the key management is weak. Key management is also a central component inMANET security. The main purpose of key management is to provide secure methods for handlingcryptographic keying algorithm. The tasks of key management includes keys for generation, distribution and maintenance. Key maintenance includes the procedures for key storage, keyupdate, key revocation, etc. In MANETs, the computational load and complexityfor key management are strongly subject to restriction by the node's available resources and thedynamic nature of network topology. A number of key management schemes have beenproposed for MANETs. In this article, we present a survey of the research work on keymanagement in MANETs according to recent publications.

title: A delay-tolerant network architecture for challenged internets
abstract: The highly successful architecture and protocols of today's Internet may operate poorly in environments characterized by very long delay paths and frequent network partitions. These problems are exacerbated by end nodes with limited power or memory resources. Often deployed in mobile and extreme environments lacking continuous connectivity, many such networks have their own specialized protocols, and do not utilize IP. To achieve interoperability between them, we propose a network architecture and application interface structured around optionally-reliable asynchronous message forwarding, with limited expectations of end-to-end connectivity and node resources. The architecture operates as an overlay above the transport layers of the networks it interconnects, and provides key services such as in-network data storage and retransmission, interoperable naming, authenticated forwarding and a coarse-grained class of service.

title: Anonymity and security in delay tolerant networks
abstract: A delay tolerant network (DTN) is a store and forward network where end-to-end connectivity is not assumed and where opportunistic links between nodes are used to transfer data. An emerging application of DTNs are rural area DTNs, which provide Internet connectivity to rural areas in developing regions using conventional transportation mediums, like buses. Potential applications of these rural area DTNs are e-governance, telemedicine and citizen journalism. Therefore, security and privacy are critical for DTNs. Traditional cryptographic techniques based on PKI-certified public keys assume continuous network access, which makes these techniques inapplicable to DTNs. We present the first anonymous communication solution for DTNs and introduce a new anonymous authentication protocol as a part of it. Furthermore, we present a security infrastructure for DTNs to provide efficient secure communication based on identity-based cryptography. We show that our solutions have better performance than existing security infrastructures for DTNs.

title: A DTN-Based Sensor Data Gathering for Agricultural Applications
abstract: This paper presents our field experience in data collection from remote sensors. By letting tractors, farmers, and sensors have short-range radio communication devices with delay-disruption tolerant networking (DTN), we can collect data from those sensors to our central database. Although, several implementations have been made with cellular phones or mesh networks in the past, DTN-based systems for such applications are still under explored. The main objective of this paper is to present our practical implementation and experiences in DTN-based data collection from remote sensors. The software, which we have developed for this research, has about 50 kbyte footprint, which is much smaller than any other DTN implementation. We carried out an experiment with 39 DTN nodes at the University of Tokyo assuming an agricultural scenario. They achieved 99.8% success rate for data gathering with moderate latency, showing sufficient usefulness in data granularity.

title: A Survey of Delay- and Disruption-Tolerant Networking Applications
abstract: Delay- and Disruption-Tolerant Networking (DTN) is a new communication paradigm that can span across multiple networks and cope with harsh conditions not envisioned in the Internet model. After more than ten years of active research in the field, numerous implementations and applications have emerged with a wide variety of performance and application domains. In this survey, we summarize recent developments in the field and highlight those areas with high potential for future development.

title: Practical security for disconnected nodes
abstract: Endpoints in a delay tolerant network (DTN) [K. Fall, 2003] must deal with long periods of disconnection, large end-to-end communication delays, and opportunistic communication over intermittent links. This makes traditional security mechanisms inefficient and sometimes unsuitable. We study three specific problems that arise naturally in this context: initiation of a secure channel by a disconnected user using an opportunistic connection, mutual authentication over an opportunistic link, and protection of disconnected users from attacks initiated by compromised identities. We propose a security architecture for DTN based on hierarchical identity based cryptography (HIBC) that provides efficient and practical solutions to these problems.

title: Applicability of identity-based cryptography for disruption-tolerant networking
abstract: Traditional approaches for communication security do not work well in disruption- and delay-tolerant networks (DTNs). Recently, the use of identity-based cryptography (IBC) has been proposed as one way to help solve some of the DTN security issues. We analyze the applicability of IBC in this context and conclude that for authentication and integrity, IBC has no significant advantage over traditional cryptography, but it can indeed enable better ways of providing confidentiality. Additionally, we show a way of bootstrapping the needed security associations for IBC use from an existing authentication infrastructure.

title: Hierarchical identity based cryptography for end-to-end security in DTNs
abstract: Delay Tolerant Networks (DTN) arise whenever traditional assumptions about todaypsilas Internet such as continuous end-to-end connectivity, low latencies and low error rates are not applicable. These challenges impose constraints on the choice and implementation of possible security mechanisms in DTNs. The key requirements for a security architecture in DTNs include ensuring the protection of DTN infrastructure from unauthorized use as well as application protection by providing confidentiality, integrity and authentication services for end-to-end communication. In this paper, we examine the issues in providing application protection in DTNs and look at various possible mechanisms. We then propose an architecture based on Hierarchical Identity Based Encryption (HIBE) that provides end-to-end security services along with the ability to have fine-grained revocation and access control while at the same time ensuring efficient key management and distribution. We believe that a HIBE based mechanism would be much more efficient in dealing with the unique constraints of DTNs compared to standard public key mechanisms (PKI).

title: A bundle of problems
abstract: Delay-Tolerant Networking” (DTN) is a neologism used for a new store-and-forward architecture and protocol suite intended for disrupted networks where there is intermittent or ad-hoc connectivity. This has been proposed as one approach to supporting delay-tolerant networks. Work in the late 1990s on the “Interplanetary Internet” forms the basis for current DTN protocols and architecture. That early work considered transport protocols robust to the hours-long propagation delays of deep-space communications. DTN is also known, primarily in military circles, as Disruption-Tolerant Networking, due to the dynamic links and outages in the military tactical environment, rather than long-delay links. In both cases, DTN technologies are well-suited to applications that are mostly asynchronous and insensitive to large variations in delivery conditions. DTN networks differ sufficiently from traditional terrestrial networks in their characteristics and connectivity that link, network and transport protocols must be carefully considered and chosen to cope with these different characteristics, or new protocols can be designed that are suited for the problems that these DTN network conditions impose. The “Bundle Protocol” exists within the DTN architecture, which sends bundles over subnet-specific transport protocols, called “convergence layers.” “Bundling” has undergone a large amount of shared development and design over a period of years as a research effort. We examine the Bundle Protocol and its related architecture closely, and discuss areas where we have found that the current Bundle approach is not well-suited to many of the operational concepts that it was intended to support. Problems with the Bundle Protocol and its convergence layers exist in mechanisms for error detection and overall reliability. This weakens the Bundle Protocol's suitability to disrupted and error-prone networks. We show that these reliability issues can lead to performance problems in DTN networks, requiring mitigation. Open research and development areas also exist with design choices in handling timing information, in determining necessary and sufficient security mechanisms, in its Quality of Service capabilities, and in other aspects of application or content identification. We show that the existing DTN bundling architecture has a number of open real-world deployment issues that can be addressed. We suggest possible remediation strategies for these weak areas of the bundle protocol that we have been working on. We also look at alternate approaches to DTN networking. Rather than only providing criticism, this paper identifies open issues, where work on modifying the Bundle Protocol is encouraged and approaches to address its various problems are suggested.

title: Delay-Tolerant Networking Security Overview
abstract: This document provides an overview of the security requirements and
mechanisms considered for delay tolerant networking security. It
discusses the options for protecting such networks and describes
reasons why specific security mechanisms were (or were not) chosen for
the relevant protocols. The entire document is informative, given its
purpose is mainly to document design decisions.

title: Leveraging Social Contacts for Message Confidentiality in Delay Tolerant Networks
abstract: Delay- and disruption-tolerant networks (DTNs) can bring much-needed connectivity to rural areas and other settings with limited or non-existing infrastructures. High node mobility and infrequent connectivity inherent to DTNs make it challenging to implement simple and traditional security services, e.g., message integrity and confidentiality.In this paper, we focus on the problem of initial secure context establishment in DTNs. Concretely, we design a scheme that allows users to leverage social contact information to exchange confidential and authentic messages. We then evaluate the proposed scheme by analyzing real-world social network data, simulating communication scenarios, and through an informal security analysis.

title: Local key management in opportunistic networks
abstract: Opportunistic networks are a new and specific type of mobile peer-to-peer networks where end-to-end connectivity cannot be assumed. These networks present compelling challenges, especially from a security perspective, as interactive protocols are infeasible in such environments. In this article, we focus on the problem of key management in the framework of content-based forwarding and opportunistic networks. After analysing this issue and identifying specific security threats such as Sybil attacks, we propose a specific key management scheme that enables the bootstrapping of local, topology-dependent security associations between a node and its neighbours along with the discovery of the neighbourhood topology, thanks to the use of pseudonym certificates and encapsulated signatures.

title: Distributed Key Establishment in Disruption Tolerant Location Based Social Wireless Sensor and Actor Network
abstract: We describe a novel Distributed Key Establishment (DKE) protocol in Disruption (Delay) Tolerant Location Based Social Wireless Sensor and Actor Networks (DTLBS-WSAN). In DKE, we propose that sensor nodes use neighboring signatures to establish their keys. Pre-distributed keys are used by actor nodes to strengthen communication security. We show that nodes can get guaranteed security when actors are connected and cover the network area and high security confidence can be achieved even without actor nodes when the adversary (malicious node) density is small. In DTLBS-WSANs, key (certificate) establishment, storage and look up are performed in a distributed way. Multiple copies of a certificate can be stored at nodes to improve key security and counter the adverse impact of network disruption.

title: Practical distributed secret key generation for delay tolerant networks
abstract: Delay tolerant networks (DTNs) are resource‐constrained dynamic networks where a continuous end‐to‐end connectivity is not always available. In such a challenging network, a fixed infrastructure may not be connected when a DTN is partitioned or the message delay in the network is large. Thus, the traditional public key infrastructure system and identity‐based encryption (IBE) system are not suitable for DTNs because they rely on centralized infrastructures and require multiple round‐trip interactions. To address this issue, we propose a distributed secret key generation system with self‐certified identity (SCI‐DKG) that does not require any private key generator and threshold cryptosystem. Initially, each node generates a private key and distributes an initial message including a self‐certified identity and secret sharings to members in a DTN. Receivers independently authenticate the identity and extracts some encryption parameters corresponding to the identity from this initial message. We prove that SCI‐DKG is chosen ciphertext secure in the standard model, and it can resist potential network attacks. Simulation results show that SCI‐DKG has smaller delay and higher successful ratio of secret key generation compared with IBE and hierarchical IBE systems implemented in a DTN.

title: Establishing initial trust in autonomous Delay Tolerant Networks without centralised PKI
abstract: A Delay Tolerant Network (DTN) is a network where nodes can be highly mobile, with long message delay times, forming dynamic and fragmented networks. Conventional centralised network security mechanisms are unsuitable in such networks, therefore distributed security solutions are more desirable in DTN implementations. Establishing effective trust in distributed systems with no centralised Public Key Infrastructure (PKI) such as the Pretty Good Privacy (PGP) scheme, usually requires human intervention. In this paper, we build and compare different decentralised trust systems for autonomous DTN. We utilise a public key distribution model based on the Web of Trust principle, and employ a simple Leverage of Common Friends (LCF) trust system to establish initial trust in autonomous DTN. We compare this system with two other scenarios (no trust and random trust) for autonomous establishment of initial trust. Comparisons are based on the time it takes to disperse the trust and resilience of the system against a malicious node distributing malicious and False Public Keys. Our results show that the LCF trust system mitigates the distribution of false malicious public keys by 40%. LCF takes 44% longer to distribute 50% of the public keys compared when using no trust system, but is 16% faster in comparison to the random trust method.

title: Public key distribution scheme for delay tolerant networks based on two-channel cryptography
abstract: A delay tolerant network (DTN) is a store carry and forward network characterized by highly mobile nodes, intermittent connectivity with frequent disruptions, limited radio range and physical obstructions. Emerging applications of DTN include rural DTN, vehicular DTN and pocket DTN. The development of DTN raises a number of security-related challenges due to inconsistent network access and unreliable end-to-end network path. One of the challenges is initial secure context establishment as it is unrealistic to assume that public key infrastructure (PKI) is always globally present and available, hence, the public key management becomes an open problem for DTN. In this paper, for the first time, we propose a dynamic virtual digraph (DVD) model for public key distribution study by extending graph theory and then present a public key distribution scheme for pocket DTN based on two-channel cryptography. By distinguishing between owners and carriers, public key exchange and authentication issues in the decentralized pocket DTN environment can be solved by a two-channel cryptography process and our simulation results have proven it.

title: Non-Interactive Key Establishment for Bundle Security Protocol of Space DTNs
abstract: To ensure the authenticity, integrity, and confidentiality of bundles, the in-transit Protocol Data Units of bundle protocol (BP) in space delay/disruption tolerant networks (DTNs), the Consultative Committee for Space Data Systems bundle security protocol (BSP) specification suggests four IPsec style security headers to provide four aspects of security services. However, this specification leaves key management as an open problem. Aiming to address the key establishment issue for BP, in this paper, we utilize a time-evolving topology model and two-channel cryptography to design efficient and noninteractive key exchange protocol. A time-evolving model is used to formally model the periodic and predetermined behavior patterns of space DTNs, and therefore, a node can schedule when and to whom it should send its public key. Meanwhile, the application of two-channel cryptography enables DTN nodes to exchange their public keys or revocation status information, with authentication assurance and in a noninteractive manner. The proposed scheme helps to establish a secure context to support for BSP, tolerating high delays, and unexpected loss of connectivity of space DTNs.

title: Bundle Security Protocol of Space DTNs Using Cryptographic Algorithm
abstract: The abstract of this paper is to asure the authenticity, integrity, and confidentiality, the in-transit Protocol Data Units of bundle protocol (BP) in space delay/disruption tolerant networks (DTNs), the Consultative Committee for Space Data Systems bundle security protocol (BSP) specification declares four IP sec style security headers to provide four aspects of security services. In any way, this specification leaves key management as an open problem. Aiming to apply the key establishment issue for Bundle Protocol, in this journal, we utilize a time- evolving topology model and two channel cryptography to design efficient and non interactive key exchange protocol . A time-evolving model is used in formal manner model the periodic and set in advance behavior patterns of space DTNs, and therefore, a system can schedule when and to whom it should send its public key. Meantime, the application of two-channel cryptography enables DTN nodes to replace their public keys or revocation status information, with authentication assurance and in a non interactive manner. The proposed scheme helps to establish a secure environment to defend for BSP, tolerating high delays, and unexpected loss of connectivity of space DTNs.

title: ID Based Cryptography and Anonymity in Delay/Disruption Tolerant Networks
abstract: Due to the rapid development in technology, every network, application needs full time connectivity without disruption and delays. The Delay/Disruption Tolerant Networking (DTN) concept is suitable for applications such as rural and disaster areas networks, animal and environmental monitoring plus others. However, due to the shared and unsecured nature of such challenged networks a good cryptographic framework needed in DTN. Identity Based Cryptography (IBC) compares favorably with traditional public key cryptography while generating public key on a fly as required. In this paper, we will provide anonymity solution in DTN using IBC. This has the advantage over public key cryptography with respect to end-to-end confidentiality. Also we use pseudonyms to provide anonymity and hide the identity of the end user.

title: Efficient Authentication and Key Agreement Protocol with Anonymity for Delay Tolerant Networks
abstract: Most of the existing authentication and key agreement protocols for delay tolerant networks are not designed for protecting privacy. In this paper, an authentication and key agreement protocol with anonymity based on combined public key is proposed. The proposed protocol eliminates the need of public key digital certificate on-line retrieval, so that any on-line trusted third party is no longer required, only needs an off-line public information repository and key generation center; and realizes mutual authentication and key agreement with anonymity between two entities. We show that the proposed protocol is secure for all probabilistic polynomial-time attackers, and achieves good security properties, including authentication, anonymity, and confidentiality and so on.

title: DakNet: rethinking connectivity in developing nations
abstract: DakNet provides extraordinarily low-cost digital communication, letting remote villages leapfrog past the expense of traditional connectivity solutions and begin development of a full-coverage broadband wireless infrastructure. What is the basis for a progressive, market-driven migration from e-governance to universal broadband connectivity that local users will pay for? DakNet, an ad hoc network that uses wireless technology to provide asynchronous digital connectivity, is evidence that the marriage of wireless and asynchronous service may indeed be the beginning of a road to universal broadband connectivity. DakNet has been successfully deployed in remote parts of both India and Cambodia at a cost two orders of magnitude less than that of traditional landline solutions.

title: PEON: privacy-enhanced opportunistic networks with applications in assistive environments
abstract: Networking holds a great deal of potential for making communications easier and more flexible in pervasive assistive environments. However, security and privacy must be addressed to make these communications acceptable with respect to protecting patient privacy. In this position paper, we propose Privacy-Enhanced Opportunistic Networking (PEON), a system for using opportunistic networking in privacy-preserving way. PEON uses concepts from anonymous communications, rerouting messages through groups of peer nodes to hide the relation between the sources and destinations. By modifying group size, we can trade off between privacy and communication overhead. Further, individual nodes can make a similar trade off by changing the number of intermediate groups. We describe the cryptographic tools needed to facilitate changes in group membership and the design of simulation experiments that we will conduct to evaluate the overhead and effectiveness of our approach.

title: Security analysis for Delay/Disruption Tolerant satellite and sensor networks
abstract: In the last few years, Delay/Disruption Tolerant Networking has grown to a healthy research topic because of its suitability for challenged environments characterized by heterogeneity, long delay paths and unpredictable link disruptions. This paper presents a DTN security architecture that focuses on the requirements for lightweight key management; lightweight AAA-like architecture for authentication/authorisation; resilience to Denial of Service attacks and user anonymity.

title: Authenticated Key Exchange (AKE) in Delay Tolerant Networks
abstract: Key exchange is considered to be a challenging problem in Delay Tolerant Networks (DTNs) operating in space environments. In this paper we investigate the options for integrating key exchange protocols with the Bundle Protocol. We demonstrate this by using a one-pass key establishment protocol. In doing so, we also highlight the peculiarities, issues and opportunities a DTN network maintains, which heavily influences the underlying security solution.

title: An Efficient, Scalable Key Transport Scheme (ESKTS) for Delay/Disruption Tolerant Networks
abstract: In the past, security protocols including key transport protocols are designed with the assumption that there are two parties communication with each other and an adversary tries to intercept this communication. In Delay/Disruption Tolerant Networking (DTN), packet delivery relies on intermediate parties in the communication path to store and forward the packets. DTN security architecture requires that integrity and authentication should be verified at intermediate nodes as well as at end nodes and confidentiality should be maintained for end communicating parties. This requires new security protocols and key management to be defined for DTN as traditional end-to-end security protocols will not work with DTN. To contribute towards solving this problem, we propose a novel Efficient and Scalable Key Transport Scheme (ESKTS) to transport the symmetric key generated at a DTN node to other communicating body securely using public key cryptography and proxy signatures. It is unique effort to design a key transport protocol in compliance with DTN architecture. ESKTS ensures that integrity and authentication is achieved at hop-by-hop level as well as end-to-end level. It also ensures end-to-end confidentiality and freshness for end communicating parties. This scheme provides a secure symmetric key transport mechanism based on public key cryptography to exploit the unique bundle buffering characteristics of DTN to reduce communication and computation cost
.

title: Fully Distributed Public Key Management through Digital Signature Chains for Delay and Disrupt Tolerant Networks
abstract: Security solutions are not easily adapted to the DTN paradigm, for example, traditional key management solutions cannot be applied in such environments. A key management scheme for DTNs must consider the dynamic topology, be self-organized and distributed and be effective in the presence of intermittent connections. There are just a few key management scheme for DTNs. Nevertheless, all of them have serious issues. They generate a huge overhead, have a single point of failure, are centralized or do not provide any security against very simple attacks. This work introduces a new key management scheme for DTNs based on chains of digital signatures (DSC-KM - Digital Signature Chains Key Management Scheme). It is decentralized, fully distributed, and does not have a single point of failure. It allows nodes to leave and joint the network at any time, works in the presence of intermittent connections, has a very small communication and memory overhead. It is based on chains of digital signatures and on a very simple chain exchange mechanism. According to simulation results, it is able to correctly and securely disseminate all certificates through the network in a short period, while maintaining the size of the chains very small. Moreover, it is able to resist to several attacks to the key management infrastructure.

title: Group Key Exchange Management in Delay Tolerant Network
abstract: Existing group key management scheme may not be applied effectively in Delay tolerant network where transmission between nodes (users) has the characteristics of irregular connectivity and long communication delay. In Previous proposed schemes, Group key is regenerated every time whenever new user joins or leave form the existing group, in order to maintain backward secrecy and forward secrecy and therefore the overhead to broadcast new group key to all member of group increases. In this proposed scheme which is based on Chinese remainder theorem constraint to broadcast new group key generated by server in case of user join as well as user leave is removed thus making the complexity constant in both scenario. Simulation is done in Opportunistic Networking Environment(ONE) Simulator and the result shows that Key update , Receiving success rate and key update success rate is better than Logical key Hierarchy LKH as well as Chinese remainder group key (CRGK) schemes.

title: Secure group communications for Delay-Tolerant Networks
abstract: The increased demand for mobile communication and use of mobile devices in high-latency, resource impoverished environments has spurred the development and growth of Delay-Tolerant Networks (DTN). DTNs aim to provide interoperability between a range of heterogeneous networks, operating under resource-constrained circumstances and traditional infrastructure networks such as the Internet. Because of the circumstances, DTNs possess some interesting characteristics that make a traditional end-to-end security paradigm unsuitable and increase the value of the overlay's resources. Controlling access to overlay resources and providing for secure group communications over unknown intermediate networks is essential. We propose a novel solution based on previous work in secure group communications using key-graphs and in extension to work on scalable access authorization in self-organizing overlays to provide a scalable mechanism for access control and secure group communications in DTNs. Since resources are especially limited, our implementation focuses on minimizing the traffic on the overlay associated with the maintenance of our solution.

title: Chinese Remainder Theorem based DTN group key management
abstract: Delay Tolerant Network (DTN) has the character of long intermittent connectivity and communication delays, which makes the existing group key management mechanism can not be effectively applied. We proposed a new Chinese Remainder Theorem based group key management mechanism for DTN. Comparing with the early scheme, the existing joined node can derive a new group key from the old group key using hash function in the new user join phase, so the server does not need to broadcast any key update message for the newly user join, and only broadcasts one message for user leave. Meanwhile, aiming at the forward security problem in the many-to-many scenarios, the time-based group key management scheme is introduced. The simulation results show that the group key update success rate, latency and message authentication success rate for our scheme is better than CRGK and LKH schemes.

title: Autonomic Group Key Management in Deep Space DTN
abstract: In deep space delay tolerant networks rekeying expend vast amounts of energy and delay time as a reliable end-to-end communication is very difficult to be available between members and key management center. In order to deal with the question, this paper puts forwards an autonomic group key management scheme for deep space DTN, in which a logical key tree based on one-encryption-key multi-decryption-key key protocol is presented. Each leaf node with a secret decryption key corresponds to a network member and each non-leaf node corresponds to a public encryption key generated by all leaf node’s decryption keys that belong to the non-leaf node’s sub tree. In the proposed scheme, each legitimate member has the same capability of modifying public encryption key with himself decryption key as key management center, so rekeying can be fulfilled successfully by a local leaving or joining member in lack of key management center support. In the security aspect, forward security and backward security are guaranteed. In the efficiency aspect, our proposed scheme’s rekeying message cost is half of LKH scheme when a new member joins, furthermore in member leaving event a leaving member makes tradeoff between computation cost and message cost except for rekeying message cost is constant and is not related to network scale. Therefore, our proposed scheme is more suitable for deep space DTN than LKH and the localization of rekeying is realized securely.

title: A Survey on Efficient Group Key Management Schemes in Wireless Networks
abstract: With the unequalled growth in Wireless networks, the associated fields of group application have also seen growth like multimedia teleconferencing, stock quoting, and distance education. Security in group applications need to be maintained which cannot be accomplished by wireless networks and IP multicast, encryptions by a shared group key is required. In this paper we review on network-independent group key management, which can be classified into three types: centralized, decentralized and distributed group key management protocols.  We Analyse key management algorithms in wireless networks and compared various factors of performance like storage overhead, commutation overhead and communication overhead during the join and leave process in groups in wireless group key management approaches, with a set of assessment parameters. In this paper we find various parameters to consider when designing a key management algorithm in wireless networks for mobile environment.  It is important to guarantee the safety of this group key and to ensure the group communication. In spite of the fact that group communication encryption can be utilized to secure messages exchanged among group individuals, distributing the cryptographic keys turn into an issue. However, various significant parameters are used to analysis security requirement of application, when the key management algorithm is developed. Strength of key management algorithms is minimization of key cost during the join/leave process of members in the groups.  In addition, we identify the relationships between the various security issues of wireless group key management like performance, security and network compatibility with regard to the algorithms discussed. It will give better idea about designing key management algorithms with minimum cost like storage, communication and computation parameters when the members join/leave from the groups. It will enable them to take better decisions.

title: Public-key infrastructure validation and revocation mechanism suitable for delay/disruption tolerant networks
abstract: Public-key infrastructure (PKI) is based on public-key certificates and is the most widely used mechanism for trust and key management. However, standard PKI validation and revocation mechanisms are considered major reasons for its unsuitability for delay/disruption tolerant networking (DTN). DTN requires mechanism to authenticate messages at each node before forwarding it in the network. So, certificate revocation lists (CRLs) being distributed in DTN network will need to be authenticated and validated for issuer certificate authority (CA) at each node. In this study, the authors propose new validation and revocation mechanism which is compliant with DTN semantics and protocols. This study also proposes a new design for CRL in compliance with standard PKI X.509 standard to make the proposed mechanism easy to implement for DTN. The new designed CRL is of reduced size as it contains fewer entries as compared with standard X.509 CRL and also arranges the revocation list in the form of hash table (map) to increase the searching efficiency.

title: Revocation and update of trust in autonomous delay tolerant networks
abstract: We model a decentralised security credential revocation and replacement scheme.We utilise leverage of common friends trust concepts for trust transferral on keys.We propose a revocation scheme to provide entity confidence and trust transferral.We compare similar schemes on key and certificate removal and replacement metrics.Proposal distributes credentials 35% faster, slowed spoofed credentials by 50%. A Delay Tolerant Network (DTN) is a dynamic, fragmented, and ephemeral network formed by a large number of highly mobile nodes. DTNs are ephemeral networks with highly mobile autonomous nodes. This requires distributed and self-organised approaches to trust management. Revocation and replacement of security credentials under adversarial influence by preserving the trust on the entity is still an open problem. Existing methods are mostly limited to detection and removal of malicious nodes. This paper makes use of the mobility property to provide a distributed, self-organising, and scalable revocation and replacement scheme. The proposed scheme effectively utilises the Leverage of Common Friends (LCF) trust system concepts to revoke compromised security credentials, replace them with new ones, whilst preserving the trust on them. The level of achieved entity confidence is thereby preserved. Security and performance of the proposed scheme is evaluated using an experimental data set in comparison with other schemes based around the LCF concept. Our extensive experimental results show that the proposed scheme distributes replacement credentials up to 35% faster and spreads spoofed credentials of strong collaborating adversaries up to 50% slower without causing any significant increase on the communication and storage overheads, when compared to other LCF based schemes.

title: Streamlined Bundle Security Protocol Specification
abstract: This document defines a streamlined bundle security protocol, which
provides data authentication, integrity, and confidentiality services
for the Bundle Protocol. Capabilities are provided to protect the
bundle payload, and additional data that may be included within the
bundle, along a single path through a network.

title: Architecture for a Delay-and-Disruption Tolerant Public-Key Distribution Network (PKDN)
abstract: Delay/Disruption Tolerant Networking (DTN) introduces a network model
in which communications can be subject to long delays and/or
intermittent connectivity. DTN specifies the use of public-key
cryptography to secure the confidentiality and integrity of messages
in transit. The use of public-key cryptography posits the need for
certification of public keys and revocation of certificates. This
document formally defines the DTN key management problem and then
provides a high-level design solution for delay and disruption
tolerant distribution and revocation of public-key certificates along
with relevant design options and recommendations for design choices.

title: Security considerations in space and delay tolerant networks
abstract: This paper reviews the Internet-inspired security work on delay tolerant networking, in particular, as it might apply to space missions, and identifies some challenges arising, for both the Internet security community and for space missions. These challenges include the development of key management schemes suited for space missions as well as a characterization of the actual security requirements applying. A specific goal of this paper is therefore to elicit feedback from space mission IT specialists in order to guide the development of security mechanisms for delay tolerant networking

title: Group Key Management Protocols: A Novel Taxonomy
abstract: Group key management is an important functional building block for any secure multicast architecture. Thereby, it has been extensively studied in the literature. In this paper we present relevant group key management protocols. Then, we compare them against some pertinent performance criteria. Multicast, Security, Group Key Management.