Conference Key Research Articles

Conference key agreement protocol with non-interactive fault-tolerance over broadcast network

Most conventional conference key agreement protocols have not been concerned with a practical situation. There may exist some malicious conferees who attempt to block conference initiation for some purposes, e.g. commercial, political or military benefit. Instances where conference must be launched immediately due to emergency, efficient detection of malicious behavior would be needed. Recently, Tzeng (IEEE Trans. Comput. 51(4):373–379, 2002) proposed a fault-tolerant conference key agreement protocol to address the issue where a conference key can be established among conferees even though malicious conferees exist. However, his protocol might be complex and inefficient during fault-detection. In the case where a malicious conferee exists and a fault-tolerant mechanism is launched, complicated interactions between conferees will be required. In this paper, we introduce a novel strategy, where any malicious conferee may be identified and removed from the conferee list without any interaction. With such a non-interactive fault-tolerance, conferences could be established and started efficiently. A complete example of our protocol will be given to describe the fascinating fault-tolerance. We analyse the security of our protocol regarding four aspects, i.e. correctness, fault-tolerance, active attack and passive attack. The comparisons of performance between our protocol and that of Tzeng are also shown. As a whole, the advantage of our protocol is superior to that of Tzeng under the situation where malicious conferees exist.

A conference key agreement protocol with fault-tolerant capability

Secure communication is of utmost importance to participants of Internet conferences. Secure communication thwarts eavesdropping. In an Internet conference, all conference participants together establish a common conference key to enable multi-party and secure exchange of messages. However, malicious conference participants may try to obtain the conference key through unfair means, and this could result in the generation of different conference keys. This paper is intended as a proposal of a new form of conference key agreement protocol. It emphasizes the filtering of malicious participants at the beginning of the conference to ensure that all participants obtain the same conference key. The proposed method also has fault-tolerant capability. Efficiency and security of a protocol is important in practice. The security of the proposed protocol is based on discrete logarithm problem assumption. The protocol is executed in computationally secure environment. The secret information of a user cannot be determined from its corresponding public information and therefore ensures privacy. Since efficiency of a protocol depends on low computation cost, the protocol attempts to achieve lower computation cost without compromising on security.

A communication-efficient and fault-tolerant conference-key agreement protocol with forward secrecy

A conference-key establishment protocol allows participants to construct a common session key that is used to encrypt/decrypt transmitted messages among the participants over an open channel. There are two kinds of conference-key establishment protocols: conference-key distribution and conference-key agreement. In a conference-key distribution protocol, a trusted or elected entity is responsible for generating and distributing the conference key. A conference-key agreement protocol involves all participants cooperatively establishing a conference key. This article designs a secure conference-key agreement protocol with constant round number and message size. Under the decision Diffie–Hellman problem assumption, the resulting protocol is demonstrated to be secure against passive adversaries. Under the random oracle model, the proposed protocol is demonstrated to be provable secure against impersonator attacks and withstand known-key attacks. Compared to previously proposed protocols with round-efficiency, the proposed protocol requires a constant message size for each participant. Furthermore, the proposed protocol possesses both fault tolerance and forward secrecy, while previously proposed protocols with round-efficiency lack one or both properties.

Analysis of a secure conference scheme for mobile communication

Dynamic participation is a feature of the secure conference schemes that allows new conferees to join and the old conferees to leave. The conferees who have left should not be able to decrypt the secure conference communication anymore. A secure conference scheme with dynamic participation was proposed in M.S. Hwang and W.P. Yang (1995) and later it was modified with the self-encryption mechanism in K.F. Hwang and C.C. Chang (2003) for a better performance. In this paper we analyze both the original scheme and the modified version. We show that both of them are subject to the active and passive attacks presented in this paper. Our active attack works in the way that a colluding group of attackers can still obtain the conference key even after they all leave the conference. The passive attack does not need any attacker to ever participate the conference. The conference key can be compromised with a large probability as long as the number of conferees is large.

Security analysis on a conference scheme for mobile communications

The conference key distribution scheme (CKDS) enables three or more parties to derive a common conference key to protect the conversation content in their conference. Designing a conference key distribution scheme for mobile communications is a difficult task because wireless networks are more susceptible to attacks and mobile devices usually obtain low power and limited computing capability. In this paper we study a conference scheme for mobile communications and find that the scheme is insecure against the replay attack. With our replay attack, an attacker with a compromised conference key can cause the conferees to reuse the compromised conference key, which in turn completely reveals subsequent conversation content.

Back Talk -- Janus Conference Key Challenges: Whacky and Non-totally Whacky Ideas

Back Talk -- Janus Conference Key Challenges: Whacky and Non-totally Whacky Ideas

Resource-aware conference key establishment for heterogeneous networks

The Diffie-Hellman problem is often the basis for establishing conference keys. In heterogeneous networks, many conferences have participants of varying resources, yet most conference keying schemes do not address this concern and place the same burden upon less powerful clients as more powerful ones. The establishment of conference keys should minimize the burden placed on resource-limited users while ensuring that the entire group can establish the key. In this paper, we present a hierarchical conference keying scheme that forms subgroup keys for successively larger subgroups en route to establishing the group key. A tree, called the conference tree, governs the order in which subgroup keys are formed. Key establishment schemes that consider users with varying costs or budgets are built by appropriately designing the conference tree. We then examine the scenario where users have both varying costs and budget constraints. A greedy algorithm is presented that achieves near-optimal performance, and requires significantly less computational effort than finding the optimal solution. We provide a comparison of the total cost of tree-based conference keying schemes against several existing schemes, and introduce a new performance criterion, the probability of establishing the session key (PESKY), to study the likelihood that a conference key can be established in the presence of budget constraints. Simulations show that the likelihood of forming a group key using a tree-based conference keying scheme is higher than the GDH schemes of Steiner et al.. Finally, we study the effect that greedy users have upon the Huffman-based conference keying scheme, and present a method to mitigate the detrimental effects of the greedy users upon the total cost.

An Improved Conference-Key Agreement Protocol with Forward Secrecy

Recently, Tzeng proposed a provably secure and fault-tolerant conference-key agreement protocol. It requires only a constant number of rounds to establish a conference key among all honest participants. This article will show that Tzeng's protocol does not offer forward secrecy. We say that a conference-key agreement protocol offers forward secrecy if the long-term secret key of any participant is compromised and will not result in the compromise of the previously established conference keys. This property is important and has been included in most key agreement protocols and standards. In this paper, an improvement based on Tzeng's protocol is proposed and it achieves forward secrecy. Under the Diffie-Hellman decision problem assumption and the random oracle model, we show that the proposed protocol can withstand passive attacks and is secure against impersonator's attacks. The improved protocol requires a constant number of rounds to compute a conference key. The improved protocol provides fault-tolerance.

Improved conference key distribution protocol based on a symmetric balanced incomplete block design

An identity-based conference key distribution protocol based on SBIBD was proposed by Chung et al. in 2002 [1]. However, this protocol suffers several problems. Consequently, participants cannot correctly authenticate one another and cannot calculate the same conference key. This study investigates these problems and proposes an improved protocol also based on SBIBD.

Attacks to Xu–Tilborg's Conference Key Distribution Scheme

In this letter, we show that Xu-Tilborg's conference key distribution scheme does not meet the forward secrecy and is vulnerable to impersonation attacks. Also, we propose a modified version which satisfies the forward secrecy and is secure against impersonation attacks.

Cryptanalysis of the Tseng-Jan Anonymous Conference Key Distribution System Without Using A One-Way Hash Function

This paper mounts a conspiracy attack on the anonymous conference key distribution system without using a one-way hash function proposed by Tseng and Jan. The attack described in the article can reveal the participants’ common key shared with the chairperson.

Comments on the Yang–Chang–Hwang anonymous conference key distribution system

Yang et al. [Comput. Stand. Interfaces 25 (2003)] proposed a conference key distribution system (CKDS) based on the elliptic curve discrete logarithm problem (ECDLP). Their scheme used a line with a hash value to broadcast the conference key. In this article, we point out that it suffers from the attack by solving linear equations to obtain the hash value h i . Thus, the conference key CK can be obtained by using the known parameter h i . We also propose an improved scheme to overcome the weakness.

The design of conference key distribution system employing a symmetric balanced incomplete block design

A conference key distribution system is a scheme to generate a conference key, and then to distribute this key to only participants attending the conference in order to communicate with each other securely. In this paper, an efficient conference key distribution system is presented by employing a symmetric balanced incomplete block design (SBIBD), one class of block designs. Through techniques for creating a conference key and for performing authentication based on identification information, the communication protocol is designed. The protocol presented minimizes the message overhead for generating a conference key. In a special class of SBIBD the message overhead is O(v v ) , where v is the number of participants. The security of the protocol, which is a significant problem in the construction of a secure system, can be proved as computationally difficult to calculate as factoring and discrete logarithms.

Application of (v, k, λ)-configuration to generation of a conference key

In order for all participants at video conference to communicate mutually, the conference key should be necessary. In this paper, we present the communication protocol that generates a conference key efficiently based on (v,k,λ)-configuration, one class of block designs, which minimizes message transmission overhead needed for this key. Especially, in the case of λ=1, the protocol requires only O(v√v) messages, where v is the number of participants.

( t, m) Threshold and generalized ID-based conference key distribution system

One strategy for distributing conference keys is for a chairman to one-way distribute the conference key to all participants. However, the chairman does not know whether the participants are present to receive the conference key or not. Thus, the number of attendants for the conference cannot be controlled, a drawback when a conference requires that the number of members exceed a certain threshold value. This paper will propose a new scheme such that only when t or more members out of m participants of the conference are on-line, can they derive the conference key. The scheme is also extended to a generalized case.

(t,m) THRESHOLD AND GENERALIZED ID-BASED CONFERENCE KEY DISTRIBUTION SYSTEM

ABSTRACT One strategy for distributing conference keys is for a chairman to one-way distribute the conference key to all participants. However, the chairman does not know whether the participants are present to receive the conference key or not. Thus, the number of attendees for the conference cannot be controlled, a drawback when a conference requires that the number of members exceed a certain threshold value. This paper will propose a new scheme such that only when t or more members out of m participants of the conference are on-line, they can derive the conference key. The scheme is also extended to a generalized case.

A conference key distribution scheme based on the theory of quadratic residues

A conference key distribution scheme based on the theory of quadratic residues is proposed in this article. In this scheme, conference key is distributed in a broadcast way and no one can impersonate the chairman to distribute the conference key. It can resist the replaying attack by using the time stamp T and authenticate the chairman. The amount of computation is small.

Modified Chen-Hwang identity-based conference key broadcast schemes with user authentication

In 1994 Chen and Hwang proposed two identity-based conference key broadcast schemes with user authentication. The conference key of their schemes can be distributed knowing only the receivers' identities. Only one copy of the ciphertexts is required to broadcast to all users. Their schemes are more efficient on transmissions and computational complexity than previous works. However, this paper identifies two problems in their schemes. Two modified schemes will be proposed to solve these problems.

Identity-based conference key broadcast schemes with user authentication

Two new ID-based conference key broadcast systems, which are very useful in constructing secure digital teleconference systems, are proposed in this paper. The conference key can be distributed knowing only the receivers' identities. Only one copy of the ciphertexts is required to broadcast to all users. The security of these new schemes is based on the difficulty of factorization, as well as that of computing the discrete logarithm modulo a composite number.

Identity-based conference key broadcast systems

Two new ID-based conference key broadcast systems are proposed. The conference key can be distributed knowing only the receivers' identities. Only one copy of the ciphertexts is required to broadcast to all users. The security of these new schemes is based on the difficulty of factorisation as well as computing the discrete logarithm. We investigate their security and give a comparison to a recently proposed scheme.