Public Key Digital Certificates Research Articles

Analyze encryption and public key infrastructure (PKI)

The researcher opens with a brief description of symmetric and asymmetric encryption systems. Then the researcher presents an analysis, comparisons of asymmetric and symmetric encryption schemes and advantages and disadvantages of PKI (Public Key Infrastructure). Asymmetric encryption systems use different transmitter and receiver keys, and it is very difficult to derive one key from the other. Symmetric systems use one shared key. PKI is a set of hardware, software, policies, and technicians to manage an environment using public key digital certificates. The researcher addresses security, PKI, and solutions within cloud technology.

Secure Communication Using Generalized Digital Certificate

A digital certificate is the combination of a statement and a signature of the statement, signed by a trusted certification authority. This work proposes using generalized digital certificate (GDC), for user authentication and key agreement for efficient secure communication. A GDC contains user’s public information, such as the information of user’s digital driver’s license, digital birth certificate, etc., and a digital signature of public information signed by a trusted certificate authority(CA). In GDC, user does not have any public and private key pairs, therefore key management in using GDC is much simpler than public key digital certificate. The digital signature component of GDC is used as the secret token of each user that will never be exposed to any verifier. Instead, the owner proves to the verifier that he has the knowledge of the signature by correctly responding to the verifier’s challenge. The session key established using proposed approach can be used for secure communication between the entities.

Efficient Authentication and Key Agreement Protocol with Anonymity for Delay Tolerant Networks

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.

Generalized Digital Certificate for User Authentication and Key Establishment for Secure Communications

Public-key digital certificate has been widely used in public-key infrastructure (PKI) to provide user public key authentication. However, the public-key digital certificate itself cannot be used as a security factor to authenticate user. In this paper, we propose the concept of generalized digital certificate (GDC) that can be used to provide user authentication and key agreement. A GDC contains user's public information, such as the information of user's digital driver's license, the information of a digital birth certificate, etc., and a digital signature of the public information signed by a trusted certificate authority (CA). However, the GDC does not contain any user's public key. Since the user does not have any private and public key pair, key management in using GDC is much simpler than using public-key digital certificate. The digital signature of the GDC is used as a secret token of each user that will never be revealed to any verifier. Instead, the owner proves to the verifier that he has the knowledge of the signature by responding to the verifier's challenge. Based on this concept, we propose both discrete logarithm (DL)-based and integer factoring (IF)-based protocols that can achieve user authentication and secret key establishment.

Efficient On-line/Off-line Signature Schemes Based on Multiple-Collision Trapdoor Hash Families

The first on-line/off-line signature scheme introduced by Even et al. in 1990 has two problems: (a) impractical signature length and (b) a one-time use of signature generated during the off-line phase. In 2001, Shamir and Tauman significantly shortened the length of the signature by using trapdoor hash families introduced by Krawczyk and Rabin in 2000. However, each trapdoor hash value and its signature in the off-line phase of Shamir and Tauman's signature scheme can be used for signing only one message in the on-line phase. In this paper, we propose multiple-collision trapdoor hash families based on discrete logarithm and factoring assumptions, and provide formal proofs of their security. We also introduce an efficient on-line/off-line signature scheme based on our proposed trapdoor hash families. Our on-line/off-line signature scheme can re-use a trapdoor hash value for signing multiple messages. If a signer includes this trapdoor hash value in the public-key digital certificate, there is no need to have any regular digital signature scheme to sign the trapdoor hash value in the off-line phase.

Design of DL-based certificateless digital signatures

Public-key cryptosystems without requiring digital certificates are very attractive in wireless communications due to limitations imposed by communication bandwidth and computational resource of the mobile wireless communication devices. To eliminate public-key digital certificate, Shamir introduced the concept of the identity-based (ID-based) cryptosystem. The main advantage of the ID-based cryptosystem is that instead of using a random integer as each user’s public key as in the traditional public-key systems, the user’s real identity, such as user’s name or email address, becomes the user’s public key. However, all identity-based signature (IBS) schemes have the inherent key escrow problem, that is private key generator (PKG) knows the private key of each user. As a result, the PKG is able to sign any message on the users’ behalf. This nature violates the “non-repudiation” requirement of digital signatures. To solve the key escrow problem of the IBS while still taking advantage of the benefits of the IBS, certificateless digital signature (CDS) was introduced. In this paper, we propose a generalized approach to construct CDS schemes. In our proposed CDS scheme, the user’s private key is known only to the user himself, therefore, it can eliminate the key escrow problem from the PKG. The proposed construction can be applied to all Discrete Logarithm (DL)-based signature schemes to convert a digital signature scheme into a CDS scheme. The proposed CDS scheme is secure against adaptive chosen-message attack in the random oracle model. In addition, it is also efficient in signature generation and verification.