• The KIPS Transactions:PartC
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• v.11C no.1
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• pp.21-30
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• 2004

Most applications using the PKI allows a user to execute the certificate validation processing. The efficiency of user system can be declined by the user-side processing resulting the overhead and low speed of the validation processing. Therefore, in this paper, we propose a new certificate validation processing method can decrease the overhead on user by allowing CAs of the hierarchical PKI to participate in the validation processing. Therefore, our proposed scheme can not only reduce the considerable overhead caused by the user-side whole processing without a new implementation of the delegated server but also improve the time spent for the processing by the reduction of the validation processing job on user.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.6
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• pp.55-65
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• 2003

To perform the certificate validation processing on the user-side application induces the very considerable overhead because of the complex and time-consuming characteristic of the validation processing. Especially, the verification for digital signature over a certificate can be the major reason of the overhead, since the verification accompanies with the cryptographic calculation over each certificate on the certificate path. In this paper, we propose a new certificate validation scheme can reduce the overhead caused by user-side certificate validation processing and improve the utilization of CAs. As the result, our proposed scheme can not only reduces the overhead for the validation processing by decreasing the cryptographic calculation but also improves the utilization of CAs by employing them to the validation processing.

• Journal of Internet Computing and Services
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• v.4 no.4
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• pp.53-64
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• 2003

To perform the certificate validation on the user-side application induces the very considerable overhead on the user-side system because of the complex and time-consuming characteristic of the validation processing. Most of the time spend for performing the validation processing is required for the digital signature verification, since the verification accompanies with the cryptographic calculation over each certificate on the certificate path. In this paper, we propose a new certificate validation scheme using DSVP(Delegated Signature Validation Protocol) which can reduce the overhead for the user-side certificate validation processing. It is achieved by delegating the digital signature verification to CAs of the PKI domain. As the proposed DSVP is the protocol performed between a user and CAs, it is applied to the hierarchical PKI efficiently and used for delegating the digital signature verification reliably and safely, our proposed scheme can not only reduces the overhead for the validation processing by decreasing the cryptographic calculation but also improves the utilization of CAs by employing them to the validation processing.

• The KIPS Transactions:PartC
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• v.10C no.4
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• pp.433-440
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• 2003

According as the real economic activities are carried out in the cyber world and the identity problem of a trade counterpart emerges, digital signature has been diffused. Due to the weakness for real-time validation using the validation method of digital signature, Certificate Revocation List, On-line Certificate Status Protocol was introduced. In this case, every transaction workload requested to verify digital signature is concentrated of a validation server node. Currently this method has been utilized on domestic financial transactions, but sooner or later the limitation will be revealed. In this paper, the validation method will be introduced which not only it can guarantee real-time validation but also the requesting node of certificate validation can maintain real-time certificate status information. This method makes the revocation management node update the certificate status information in real-time to the validation node while revoking certificate. The characteristic of this method is that the revocation management node should memorize the validation nodes which a certificate holder uses. If a certificate holder connects a validation node for the first time, the validation node should request its certificate status information to the above revocation management node and the revocation management node memorizes the validation node at the time. After that, the revocation management node inform the revocation information in real-time to all the validation node registered when a request of revocation happens. The benefits of this method are the fact that we can reduce the validation time because the certificate validation can be completed at the validation node and that we can avoid the concentration of requesting certificate status information to a revocation node.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.12C
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• pp.1722-1728
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• 2004

To discover a certificate path is a very important topic in the PKI with a lot of candidate paths. The certificate path discovery processing is executed via many verifications and as the number of verification times increases, the validity of the discovered path becomes high. The selection of the path with high validity provides high-speed certificate validation by reducing the number of repetition times of path discovery and validation processing. Otherwise, there is a problem that the speed and computation overheads are increased. In this paper, we propose an efficient certificate path discovery algorithm can make high the certificate validity with low overhead.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9C
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• pp.908-922
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• 2003

The Public Key Infrastructure (PKI) trends to delegate the certificate path processing to the Delegated Path Discovery (DPD) Server and Delegated Path Validation (DPV) server recently. The most critical factor for the selection of the delegated server is to allow the server to be equipped with a high reliability through a low cost, and simple implementation. In this paper, we propose a new certificate path processing scheme employed the trusted CA as the DPD/DPV server by adding the capability of the Validation Authority (VA) to the trusted CA. Since our proposed scheme uses the existing trusted CA as validation server, we can achieve a high trust through a simple implementation for the processing. Besides, we propose an additional scheme for reducing an overhead on the trusted CA. it is obtained by delegating digital signature verification to CAs on the path and by skipping the repeated path processing. As the result, our proposed validation scheme can be performed efficiently with high speed and low computational overhead.

• The Journal of the Korea Contents Association
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• v.5 no.1
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• pp.45-53
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• 2005

With the rapid progress of research to offer a convenience of mobile communication, the mobile users can use not only the services of voice call but also the variety services of data communication using Internet. These include Internet Searching, Internet Shopping and Internet banking and Internet stock exchange and electronic payment and so on, based on PKI. Also, the need of data communication between the mobile users has been increased. As it is possible for mobile users to do user authentication, key distribution, encryption, decryption and so on, it is needed the certificate status validation between the mobile users. However due to the PCS(Personal Communication System) had been only designed and implemented for voice call between the mobile users, it is not easy to apply data communication between the mobile users on PKI. Therefore the study of for the data communication between the mobile users in PCS is a few. It is for the data transfer between the mobile users to communicate using call processing of PCS. So, we propose how to process the certificate status validation during call processing for data communication between the mobile users in the PCS.

• The KIPS Transactions:PartC
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• v.13C no.2 s.105
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• pp.147-154
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• 2006

The certificate status validation mechanism is a critical component of a public key infrastructure based on certificate system. The most generally mechanisms used these days are the use of the certificate revocation list and the real-time certificate status protocol. But the certificate revocation list can not give the real-time certificate status because the certificate is being delivered periodically, and the real-time certificate status protocol method will generate a concentrated load to the server because the protocol in the central server will be accessed whenever a certification is necessary. It will also take a long time to validate the certificate because each trade has to send mass information through the network. This paper will present that real-time validation is guaranteed as the real-time certificate status protocol method and the traffic congestion in the network Is reduced in a way that the certification would be requested using the user information hash value and would be validated using the user information kept in the certification authorities and the service providers. Based on the this study, we suggest a real-time certificate status validation mechanism which can reduce the certificate status validation time using the signed user information hash value. And we confirm speed of certificate status verification faster than existing CRL(Certificate Revocation List) and OCSP(Online Certificate Status Protocol) method by test.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1107-1110
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• 2004

PKI(Public key Infrastructure)기반에서 CA(Certificate Authority)는 사용자를 인증하기 위해서 인증서를 생성하고, 인증서의 상태를 검증하기위해서 CRL(Certificate Revocation List)를 발행하여 인증서 취소 상태를 확인하도록 한다. CRL을 사용할 경우 사용자의 증가로 인하여 CRL의 크기가 증가 함으로써 많은 부담과 실시간 처리가 어렵다. 이와 같은 단점을 보안하기 위해서 최근에는 실시간 처리가 가능한 OCSP(Online Certificate Status Protocol)방법이 제안되었지만 이 또한 사용자의 급증으로 하나의 OCSP 서버에 집중화 됨으로써 OCSP 서버의 부하가 많이 생긴다. 본 논문에서는 집중 OCSP 서버에서 생기는 부하를 줄이기 위해 여러 개의 OCSP 서버를 두고, 각 OCSP 서버의 응답 처리 시간을 빠르게 하기 위해서 CA가 실시간으로 인증서 취소 정보를 해당 OCSP 서버에게 분배하여 전달하고 Front Server를 둠으로써 각 OCSP의 Load를 모니터링하여 부하가 적게 걸린 OCSP에게 인증서 상태 검증을 함으로써 신뢰성과 각 OCSP 서버의 부하를 줄이는 방안을 제시한다.

• Journal of Information Processing Systems
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• v.1 no.1 s.1
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• pp.86-95
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• 2005

Location-based services or LBS refer to value-added service by processing information utilizing mobile user location. With the rapidly increasing wireless Internet subscribers and world LBS market, the various location based applications are introduced such as buddy finder, proximity and security services. As the killer application of the wireless Internet, the LBS have reconsidered technology about location determination technology, LBS middleware server for various application, and diverse contents processing technology. However, there are fears that this new wealth of personal location information will lead to new security risks, to the invasion of the privacy of people and organizations. This paper describes a novel security approach on open LBS service to validate certificate based on current LBS platform environment using XKMS (XML Key Management Specification) and SAML (Security Assertion Markup Language), XACML (extensible Access Control Markup Language) in XML security mechanism.