A recent primitive known as asymmetric group key agreement (AGKA) allows a group of users to negotiate a common encryption key which is accessible to any entities and corresponds to different decryption keys, each of which is only computable by one group member. This concept makes it easy to construct distributed and one-round group key agreement protocols. However, this existing instantiation depends on public key infrastructure (PKI) associated with certificate management, or it is only secure against passive adversaries. This paper addresses this concern by designing a certificateless authenticated AGKA scheme, which does not require certificates to guarantee the authenticity of public keys yet avoids the inherent escrow problem of identity-based cryptosystems. Using simple binding techniques, the proposed scheme can be raised to the same trust level as that using the traditional PKI. We show that the proposed protocol is secure provided that the underlying k-bilinear Diffie–Hellman exponent problem is hard.
A recent primitive known as asymmetric group key agreement (AGKA) allows a group of users to negotiate a common encryption key which is accessible to any entities and corresponds to different decryption keys, each of which is only computable by one group member. This concept makes it easy to construct distributed and one-round group key agreement protocols. However, this existing instantiation depends on public key infrastructure (PKI) associated with certificate management, or it is only secure against passive adversaries. This paper addresses this concern by designing a certificateless authenticated AGKA scheme, which does not require certificates to guarantee the authenticity of public keys yet avoids the inherent escrow problem of identity-based cryptosystems. Using simple binding techniques, the proposed scheme can be raised to the same trust level as that using the traditional PKI. We show that the proposed protocol is secure provided that the underlying k-bilinear Diffie–Hellman exponent problem is hard.
Group key agreement (GKA) is a cryptographic primitive allowing two or more users to negotiate a shared session key over public networks.Wu et al. recently introduced the concept of asymmetric GKA that allows a group of users to negotiate a common public key, while each user only needs to hold his/her respective private key.However, Wu et al.'s protocol can not resist active attacks, such as fabrication.To solve this problem, Zhang et al. proposed an authenticated asymmetric GKA protocol, where each user is authenticated during the negotiation process, so it can resist active attacks.Whereas, Zhang et al.'s protocol needs a partially trusted certificate authority to issue certificates, which brings a heavy certificate management burden.To eliminate such cost, Zhang et al. constructed another protocol in identity-based setting.Unfortunately, it suffers from the so-called key escrow problem.In this paper, we propose the certificateless authenticated asymmetric group key agreement protocol which does not have certificate management burden and key escrow problem.Besides, our protocol achieves known-key security, unknown key-share security, key-compromise impersonation security, and key control security.Our simulation based on the pairing-based cryptography (PBC) library shows that this protocol is efficient and practical.
Abstract. In identity-based public-key cryptography, an entity’s public key can be easily derived from its identity. The direct derivation of public keys in identity-based public-key cryptography eliminates the need for certificates and solves certain public key management problems in traditional public-key cryptosystems. Recently, the notion of asymmetric group key agreement was introduced, in which the group members merely negotiate a common encryption key which is accessible to any entity, but they hold respective secret decryption keys. In this paper, we first propose a security model for identity-based authenticated asymmetric group key agreement (IB-AAGKA) protocols. We then propose an IB-AAGKA protocol which is proven secure under the Bilinear Diffie-Hellman Exponent assumption. Our protocol is also efficient, and readily adaptable to provide broadcast encryption.
With the development of multiuser online meetings, more group-oriented technologies and applications for instance collaborative work are becoming increasingly important.Authenticated Group Key Agreement (AGKA) schemes provide a shared group key for users with after their identities are confirmed to guarantee the confidentiality and integrity of group communications.On the basis of the Public Key Cryptography (PKC) system used, AGKA can be classified as Public Key Infrastructure-based, Identity-based, and Certificateless.Because the latter type can solve the certificate management overhead and the key escrow problems of the first two types, Certificateless-AGKA (CL-AGKA) protocols have become a popular area of research.However, most CL-AGKA protocols are vulnerable to Public Key Replacement Attacks (PKRA) due to the lack of public key authentication.In the present work, we present a CL-AGKA scheme that can resist PKRA in order to solve impersonation attacks caused by those attacks.Beyond security, improving scheme efficiency is another direction for AGKA research.To reduce the communication and computation cost, we present a scheme with only one round of information interaction and construct a CL-AGKA scheme replacing the bilinear pairing with elliptic curve cryptography.Therefore, our scheme has good applicability to communication environments with limited bandwidth and computing capabilities.
Asymmetric group key agreement allows a group of users to negotiate a public encryption key that corresponds to several decryption keys, and each decryption key can only be computed by one group member. This novel notion ensures the confidentiality of communication among group members and allows any external entity to send messages to the group. However, the existing authenticated asymmetric group key agreement protocols are designed in identity-based cryptosystem or certificateless public key cryptosystem, which are not widely deployed. In this paper, we propose an efficient authenticated asymmetric group key agreement protocol. The protocol captures the security of secrecy, known-key security, key-compromise impersonation, unknown key-share and key control while being resistant to active attacks. The security of our protocol is reduced to the k-BDHE problem.
Modern collaborative and group-oriented applications typically involve communications over open networks. Given the openness of today's networks, communications among group members must be secure and, at the same time, efficient. Group key agreement (GKA) is widely employed for secure group communications in modern collaborative and group-oriented applications. This paper studies the problem of GKA in identity-based cryptosystems with an emphasis on round-efficient, sender-unrestricted, member-dynamic, and provably secure key escrow freeness. The problem is resolved by proposing a one-round dynamic asymmetric GKA protocol which allows a group of members to dynamically establish a public group encryption key, while each member has a different secret decryption key in an identity-based cryptosystem. Knowing the group encryption key, any entity can encrypt to the group members so that only the members can decrypt. We construct this protocol with a strongly unforgeable stateful identity-based batch multisignature scheme. The proposed protocol is shown to be secure under the k -bilinear Diffie-Hellman exponent assumption.
Key agreement protocols are multi-party protocols in which entities exchange public information allowing them to create a common secret key that is known only to those entities and which cannot be predetermined by any party. Recently, the notion of certificateless public key cryptography was introduced to mitigate the heavy certificate management burden in traditional public key infrastructure and key escrow problem in ID-based cryptosystem. In this paper, we present an efficient certificateless three-party authenticated key agreement protocol based on certificateless signature scheme. We show that the proposed protocol is secure (i.e. conforms to defined security attributes) while being efficient.