• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.347-349
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• 2008

The primitive of Identity-Based Broadcast Encryption allows a sender to distribute session keys or messages for a dynamically changing set of receivers using the receiver's identity as a public key. We already know that the trade-off exists the efficiency between the public parameter size and the ciphertext size. So, if the ciphertext size is O(1), then the public parameter size may be O(n). Some of IBBE scheme take the public parameters as input in decryption phase. Thus, a decryption device (or client) has to store the public parameters or receive it. This means that a decryption device (or client) has to have the proper size storage. Recently, delerabl$\square$e proposed an IBBE which have the O(1) size ciphertexts and the O(n) size public parameters. In this paper, we present an IBBE scheme. In our construction the ciphertext size and the public parameter size are sub-linear in the total number of receivers, and the private key size is constant.

• Journal of KIISE:Information Networking
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• v.33 no.1
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• pp.9-15
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• 2006

While a lot of important information is being sent and received on the Internet, the information could be exposed to many threats, and the more the Multicast Service is various and generalized, the more the service range is widened. When a new member joins in or leaves from the Multicast Group, the Group Key, which the existing member use for, should be newly updated. The existing method had a problem that the performance was depreciated by the key exchanging. This paper proposes the effective group management mechanism for a secure transmission of the Multicast Data on the Multicast Group.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.5
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• pp.23-36
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• 2004

This paper presents a password based authentication and key exchange protocol which can be used for both authenticating users and exchanging session keys for a subsequent secure communication over an untrusted network. Our idea is to increase a randomness of the password verification data, i.e., we split the password, and then amplify the split passwords in the high entropy-structured password verification data. And in order to prevent the verifier-compromised attack, we construct our system such that the password verification data is encrypted with the verifier's key and the private key of verifier used to encrypt it is stored in a secure place like a smart cards. Also we propose the distributed password authentication scheme utilizing many authentication servers in order to prevent the server-compromised attack occurred when only one server is used. Furthermore, the security analysis on the proposed protocol has been presented as a conclusion.

• Journal of Internet Computing and Services
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• v.6 no.3
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• pp.17-30
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• 2005

A PAK(Password-Authenticated Key Exchange) protocol is used as a protocol to provide both the mutual authentication and allow the communication entities to share the session key for the subsequent secure communication, using the human-memorable portable short-length password, In this paper, we propose distributed key exchange protocols applicable to a smartcard using the MTI(Matsumoto, Takashima, Imai) key distribution protocol and PAK protocol. If only one server keeps the password verification data which is used for password authentication protocol. then It could easily be compromised by an attacker, called the server-compromised attack, which results in impersonating either a user or a server, Therefore, these password verification data should be distributed among the many server using the secret sharing scheme, The Object of this paper Is to present a password-based key exchange protocol which is to allow user authentication and session key distribution, using the private key in a smartcard and a password typed by a user. Moreover, to avoid the server-compromised attack, we propose the distributee key exchange protocols using the MTI key distribution protocol, And we present the security analysis of the proposed key exchange protocol and compare the proposed protocols with the existing protocols.

• The KIPS Transactions:PartC
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• v.11C no.2
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• pp.149-156
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• 2004

Broadcast encryption schemes are applied to transmit digital informations of multimedia, software, Pay-TV etc. in public network. Important thing is that only user who is permitted before only must be able to get digital information in broadcast encryption schemes. If broadcast message transfers, users who authority is get digital information to use private key given in the advance by oneself. Thus, user acquires message or session key to use key that broadcaster transmits, broadcaster need process that generation and distribution key in these process. Also, user secession new when join efficient key renewal need. In this paper, introduce about efficient key generation and distribution, key renewal method. Take advantage of two technique of proposal system. One is method that server creates key forecasting user without user's agreement, and another is method that server and user agree each other and create key Advantage of two proposal system because uses a secret key broadcast message decryption do can and renewal is available effectively using one information whatever key renewal later.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.3
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• pp.1-6
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• 2015

The IoT(Internet of things) technology enable objects around user to be connected with each other for sharing information. To support security is the mandatory requirement in IoT because it is related to the disclosure of private information but also directly related to the human safety. However, it is difficult to apply traditional security mechanism into lightweight devices. This is owing to the fact that many IoT devices are generally resource constrained and powered by battery. PSK(Pre-Shared Key) based approach, which share secret key in advance between communication entities thereafter operate security functions, is suitable for light-weight device. That is because PSK is costly efficient than a session key establishment approach based on public key algorithm. However, how to safely set a PSK of the lightweight device in advance is a difficult issue because input/output interfaces such as keyboard or display are constrained in general lightweight devices. To solve the problem, we propose and develop a secure PSK configuration scheme for resource constrained devices in IoT.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.3
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• pp.657-663
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• 2010

Today, rapid evolution of Internet makes various types of services in ubiquitous environment are intelligent and active. As a result, user's demand on high quality of life increases and health care service based on ubiquitous environment draws a lot of attention. However, user's private information used for health care service is illegally distributed and exposed, causing serious individual and social problems. Therefore, this thesis is intended to suggest a secure health care service to prevent unauthorized third party's access and to protect user's privacy in health care systems. The proposed scheme establishes a session key through communication channel between health care system and user based on explicit mutual authentication and provides secure communication and access control, improving security as one of the leading health care systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1597-1605
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• 2015

Password authenticated key exchange (PAKE) is a protocol that a client stores its password to a server, authenticates itself using its password and shares a session key with the server. In multi-server PAKE, a client splits its password and stores them to several servers separately. Unless all the servers are compromised, client's password will not be disclosed in the multi-server setting. In attribute-based encryption (ABE), a sender encrypts a message M using a set of attributes and then a receiver decrypts it using the same set of attributes. In this paper, we introduce multi-server PAKE protocol that utilizes a set of attributes of ABE as a client's password. In the protocol, the client and servers do not need to create additional public/private key pairs because the password is used as a set of public keys. Also, the client and the servers exchange only one round-trip message per server. The protocol is secure against dictionary attacks. We prove our system is secure in a proposed threat model. Finally we show feasibility through evaluating the execution time of the protocol.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5C
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• pp.737-749
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• 2004

Kerberos authenticates clients using symmetric-key cryptography, and supposed to Oust other systems of the realm in distributed network environment. But, authentication and authorization are essential elements for the security. In this paper, we design an efficient and secure authentication/authorization mechanism by introducing the public/private-key and installing the proxy privilege server to Kerberos. In the proposed mechanism, to make a system more secure, the value of the session key is changed everytime using MAC(message authentication code) algorithm with the long-term key for user-authentication and a random number exchanged through the public key. Also, we reduce the number of keys by simplifying authentication steps. Proxy privilege server certifies privilege request of client and issues a privilege attribute certificate. Application server executes privilege request of client which is included a privilege attribute certificate. Also, a privilege attribute certificate is used in delegation. We design an efficient and secure authentication/authorization algorithm with Kerberos.

• Journal of KIISE:Information Networking
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• v.34 no.1
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• pp.62-72
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• 2007

Mobile Virtual Private Network (MVPN) provides VPN services without geographical restriction to mobile workers using mobile devices. Coexistence of Mobile IP (MIP) protocol for mobility and IPsec-based VPN technology are necessary in order to provide continuous VPN service to mobile users. However, Problems like registration failure or frequent IPsec tunnel re-negotiation occur when IPsec-based VPN Gateway (GW) and MIP are used together. In order to solve these problems, IETF proposes a mechanism which uses external home agent (x-HA) located external to the corporate VPN GW. In addition, based on the IETF proposal, a mechanism that assigns x-HA dynamically in the networks where MN is currently located was also proposed with the purpose to reduce handover latency as well as end-to-end delay. However, this mechanism has problems such as exposure of a session key for dynamic Mobility Security Association (MSA) or a long latency in case of the handover between different networks. In this paper, we propose a new MVPN protocol in order to minimize handover latency, enhance the security in key exchange, and to reduce data losses cause by handover. Through a course of simulation, the performance of proposed protocol is compared with the existing mechanism.