Most of the existing cryptographic schemes, e.g., key agreement protocol, call for good randomness. Otherwise, the security of these cryptographic schemes cannot be fully guaranteed. Nonce-based cryptosystem is recently introduced to improve the security of public key encryption and digital signature schemes by ensuring security when randomness fails. In this paper, we first investigate the security of key agreement protocols when randomness fails. Then we define the security model for nonce-based key agreement protocols and propose a nonce-based key agreement protocol that protects against bad randomness. The new protocol is proven to be secure in our proposed security model.
Most of the existing cryptographic schemes, e.g., key agreement protocol, call for good randomness. Otherwise, the security of these cryptographic schemes cannot be fully guaranteed. Nonce-based cryptosystem is recently introduced to improve the security of public key encryption and digital signature schemes by ensuring security when randomness fails. In this paper, we first investigate the security of key agreement protocols when randomness fails. Then we define the security model for nonce-based key agreement protocols and propose a nonce-based key agreement protocol that protects against bad randomness. The new protocol is proven to be secure in our proposed security model.
This paper presents an identity-based key agreement protocols that are provably secure without random oracles(namely,in the standard model).It is inspired by a new identity-based encryption scheme first proposed by Gentry.This paper details how this key agreement can be used in either escrowed or escrowless mode.All the proposed protocols are compared performance(with respect to computational and communication efficiencies) to all known protocols that are only proven secure in the random oracle model.
Abstract—In this paper, we present a two-party attribute-based key agreement protocol, which is secure in the standard model (without random oracles), under the truncated decision q-ABDHE assumption. Then we give a modified version of this scheme, in which the users can be revoked efficiently. The attribute-based key agreement protocol is based on the attribute-based encryption scheme, which is a generalization of identity-based cryptosystems, incorporates attributes as inputs to its cryptographic primitives. These kinds of schemes not only preserve the advantages of traditional identity-based key agreement protocol, but also provide some new properties, such as hiding the identity information of the individual, increasing the flexibility of key management, and providing efficient means to revoke users from the system. Index Terms—attribute-based key agreement, without random oracles, revocation I.
Key agreement and digital signature are two significant and most useful contributions of modern cryptography. Such protocols and schemes allow two or more parties to establish a common session key securely in the presence of a malicious adversary and provide means of ensuring data origin authentication, data integrity and non-repudiation. Thus, secure key agreement protocols and signature schemes are fundamental building blocks for constructing complex higher-level protocols.
In this thesis, we deal with security analysis of existing key agreement protocols and digital signature schemes. We examine ten authenticated key agreement protocols without key confirmation, out of which half are two-party and the other half are three-party, and one deterministic identity-based aggregate signature scheme. By giving concrete attacks, we show that these protocols and the scheme do not possess the desirable security attributes or security attributes claimed by their authors. We also present a secure deterministic identity-based signature scheme that supports partial aggregation.
First, we show that Okamoto's and Chen et al.’s protocol cannot withstand the key-compromise impersonation attack and that Tan et al.’s, Lim et al.’s and two protocols of Holbl et al. are insecure against the impersonation attack and the man-in-the-middle attack. Next, we prove that one protocol of Holbl et al. is vulnerable to the insider attack, one to the unknown key-share attack, one protocol allows an adversary to compute the private key of any user and one protocol allows her to compute the shared session key. We also show that Selvi et. al.'s deterministic identity-based aggregate signature scheme is universally forgeable, i.e., anyone is able to easily generate valid signatures on any messages of his choice having on average twelve genuine digital signatures.
In the end, we introduce a new deterministic identity-based signature scheme and formally prove its security in the random oracle model. The scheme is a major improvement of the signature scheme proposed by Selvi et. al. and offers the same tight security reduction to the underlying gap Diffie-Hellman problem. Because the newly proposed scheme is deterministic it allows partial aggregation, i.e., all the signatures from the same signer can be aggregated into one single short signature.
A bad randomness may cause catastrophic results in security; thus, it is of importance to make cryptographic systems secure against bad randomness. In this paper, we focus on a practical situation where an adversary is able to force participants in an authenticated key exchange (AKE) system to reuse the random values and the functions of these values, called related randomness attack (RRA). Following the existing randomness resetting security model of AKE and the RRA security model of public-key encryption, we present a model of RRA security for authenticated key exchange, as well as the necessary restrictions on the related randomness functions used to obtain the security definition. Then we show how a related randomness attack adversary breaks the security of some existing AKE protocols, and propose some constructions of RRA-secure authenticated key exchange in the random oracle model and standard model, respectively.
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.
Authenticated key agreement protocol is one of the important cryptographic primitives to ensure secure communication in an open network. Certificateless public key cryptography (CL-PKC) represents an interesting and potentially useful balance between public key cryptography based on certificates and identity-based cryptography. The topic of CL-PKC has undergone quite rapid development with schemes being proposed for encryption and signatures, while certificateless authenticated key agreement protocols are seldom discussed. In this paper, we present a secure two-party authenticated key agreement protocol based on an efficient certificateless public key encryption with pairing. Such a scheme achieves almost all of the security attributes, including known-key secrecy, perfect forward secrecy, PKG forward secrecy, key-compromise impersonation resilience, unknown key-share resilience, known session-specific temporary information security, message independence and no key control. Meanwhile, it is also practical with nice efficiency.