• Journal of KIISE:Information Networking
• /
• v.30 no.4
• /
• pp.484-493
• /
• 2003

Proxy signature scheme is a cryptographic protocol that an original signer delegates her signing capability to a proxy signer, and then the proxy signer is able to create signatures on behalf of the original signer. In general, there is time-limit for which the signing capability of the proxy signer is valid. One of methods to limit the valid delegation time is to make public delegation information contain the expiration date of the delegation. however, in this method we cannot prevent the proxy signer from signing after the valid delegation is expired because no one knows the exact time when the proxy signer signed a message. The validity of the past legal signatures cannot be preserved in case that the proxy singer´s key is compromised during the delegation period. In this paper, we propose a new scheme, time-limited forward-secure proxy signature protocol, which prevents the proxy singer from signing after the valid delegation is expired and which preserves the validity of the past legal signatures even if the signing key is compromised. The proposed scheme does not require the exact time-information by making an original signer control time-related parameters and satisfies the forward-security property in each update-period of the proxy signing key. The time-period is determined according to the application characteristics or security policies.

• Journal of KIISE:Computer Systems and Theory
• /
• v.31 no.8
• /
• pp.465-472
• /
• 2004

Proxy signatures is a signature scheme that an original signer delegates one's signature capability to a proxy signer, and then the proxy signer creates a signature on behalf of the original signer. Delegation of authority is a common practice in the real world, in particular, it happens naturally in hierarchical groups such as company, bank and army, etc. In this paper, we propose a new dynamic multi-proxy signature scheme allowing repetitive delegations in a hierarchical group. We adopt multi-proxy signatures to enhance the security of proxy signature. In multi-proxy signatures, plural proxy signers can generate a valid proxy signature collectively on behalf of one original signer. In our scheme, the proxy group is not fixed but constructed dynamically according to some situations. Delegations are processed from higher level to lower level in the hierarchy using delegation tickets. When the original signer wants to delegate one's signature authority, the original signer generates a delegation ticket based on secret sharing and Diffie-Hellman problems. The delegation ticket is shared among proxy signers and then all the proxy signers can generate a valid proxy signature collectively by reconstructing the original signer's delegation ticket. If a certain proxy signer can not attend the proxy signature generating protocol, the proxy signer can also delegate repetitively his partial signature authority to the lower level participants, and then the proxies are constructed dynamically.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
• /
• 1997.11a
• /
• pp.34-40
• /
• 1997

By proxy signatures, proposed by Mambo, a designated signer can sign original's signature instead of original signer. This paper presents new types of digital proxy signatures called partial delegation with threshold delegation. In proxy signatures for partial delegation with threshold delegation, the proxy signer's power to sign messages is shared. In conclusion, we construct proxy signature schemes satisfying our conditions.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.17 no.3
• /
• pp.17-25
• /
• 2007

Delegation of signing capability is a common practice in various applications. Mambo et al. proposed a proxy signatures as a solutions for delegation of signing capability. Proxy signatures allow a designated proxy signer to sign on behalf of an original signer. After the concept of proxy signature scheme is proposed, many variants are proposed to support more general delegation setting. To capture all possible delegation structures, the concept of delegation network was proposed by Aura. ID-based cryptography, which is suited for flexible environment, is desirable to construct a delegation network. Chow et al proposed an ID-based delegation network. In the computational point of view, their solution requires E pairing operations and N elliptic curve scalar multiplications where E and N are the number of edges and nodes in a delegation structure, respectively. In this paper, we proposed an efficient ID-based delegation network which requires only E pairing operations. Moreover, we can design a modified delegation network that requires only N pairing operations.

• Convergence Security Journal
• /
• v.4 no.2
• /
• pp.35-41
• /
• 2004

Proxy signature scheme based on delegation of warrant is studied in these days. Proxy signature Is a signature scheme that the original signer delegates his signing warrant to the proxy signer, and the proxy signer creates a signature on behalf of the original signer. For using this scheme, the security for protecting from the forgeability or misuse is necessary. There are several security requirements for using the proxy signature schemes. In this paper we suggest the proxy-register protocol scheme that original signer registers to the verifier about the proxy related information. In our scheme, verifier verifies the signature that original signer creates about the proxy information and sets the warrant of proxy signer, validity period for proxy signature and some limitation. Finally, we will show the advantages of our suggestion by comparing with the previous proxy signature schemes.

• The KIPS Transactions:PartC
• /
• v.10C no.6
• /
• pp.739-746
• /
• 2003

In real life, we frequently use th proxy signatrue by delegating one's own privileges. It is necessary to distribute the data related to privilege delegation securely in order to use such a proxy signature in the Internet. However, inorder to use the secure proxy signature, we need to have some mechanism to prevent a proxy signer from misuse of privileges by applying proxy certificate and a privilege delegation mechanism to manage information with related to privilege delegarion. In addition, we have implemented the prototype to demonstrate the possible proxy signature service using proxy certificate.

• Proceedings of the IEEK Conference
• /
• summer
• /
• pp.52-56
• /
• 2004

Computing today is becoming ubiquitous. In such ubiquitous computing environments, entities expect to access resources and services at any time from anywhere. Therefore, the question rises of how to establish trust relationship in previously unknown devices or resources with such environment. After reviewing a model to delegate trust to communicating entities in ubiquitous environment and its security problems, we present a new model for secure delegation over communication entities. We adopt two-party signature scheme as cryptographic primitives. Additionally, we apply threshold cryptosystems to our model for more secure enhancement.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.2
• /
• pp.361-365
• /
• 2005

Proxy signature schemes which allows original signer to delegate proxy signer to sign message on its behalf have a considerable amount of interest from researchers since Mambo[1] and have found many practical applications such as distributed network, Grid computing and electronic commerce. Araki[6] extended them to multi-level proxy signature. But it could not satisfy some security requirement. In this paper we propose a protocol to delegate signing right to another entity for multi-level proxy signature. Our protocol do not require secure channel and guarantee that nobody is able to repudiate delegation or acceptance of signing right, it is impossible for anyone to generate signature except designed and original signer can withdraw the delegation before expiration if it is necessary.

• Journal of Digital Convergence
• /
• v.12 no.1
• /
• pp.389-395
• /
• 2014

In a biometric signature scheme, a user's biometric key is used to sign the document. It also requires the user be authenticated with biometric recognition method, prior to signing the document. Because the biometric recognition is launched every time the signature session started, it is not suitable for electronic commerce applications such as shopping malls where large number of documents to sign are required. Therefore, to commercialize biometric based signature schemes, the new proxy signature scheme is needed to ease the burden of the signer. In the proxy signature scheme, the signer can delegate signing activities to trustful third parties. In this study, the biometric based signature delegation method is proposed. The proposed scheme is suitable for applications where a lot of signing are required. It is consisted of biometric key generation, PKI based mutual authentication, signature generation and verification protocols.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.47 no.1
• /
• pp.91-98
• /
• 2010

This paper proposes authority delegation for secure social community creation and mutual authentication scheme between the community members using proxy signature in community-based ubiquitous networks. In community-based ubiquitous network, User's context-awareness information is collected and used to provide context-awareness network service and application service for someone who need it. For the many reason, i.e. study, game, information sharing, business and conference, social community could be created by members of a social group. However, in community-based ubiquitous network, this kind of the context-awareness information could be abused and created by a malicious nodes for attack the community. Also, forgery community could be built up to attack the community members. The proposed scheme using the proxy signature provides a mutual authentication and secure secret key exchange between community members, and supports secure authority delegation that can creates social community. Also, when delegation of signing authority and mutual authentication, this scheme reduces total computation time compared to the RSA signature scheme.