• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.3
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• pp.473-483
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• 2012

To achieve an entire end-to-end security, the classical authentication setting such that all participants have a same password is not practical since a password is not a common secret but a personal secret depending on an individual. Thus, an efficient client to client different password-based authenticated key agreement protocol (for short, EC2C-PAKA) has been suggested in the cross-realm setting. Very recently, however, a security weakness of the EC2C-PAKA protocol has been analyzed by Feng and Xu. They have claimed that the EC2C-PAKA protocol is insecure against a password impersonation attack. They also have presented an improved version of the EC2C-PAKA protocol. In this paper, we demonstrate that their claim on the insecurity of EC2C-PAKA protocol against a password impersonation attack is not valid. We show that the EC2C-PAKA protocol is still secure against the password impersonation attack. In addition, ironically, we show that the improved protocol by Feng and Xu is insecure against an impersonation attack such that a server holding password of Alice in realm A can impersonate Bob in realm B. We also discuss a countermeasure to prevent the attack.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.3
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• pp.547-557
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• 2015

The security of all cryptographic algorithms and protocols is based on the confidentiality of secret keys. Key management mechanism is an indispensable part of the cryptographic system and this deals with the generation, exchange, storage, use, and replacement of keys. Within the key management mechanism there are key derivation functions (KDFs) which derive one or more keys from a master key. NIST specifies three families of PRF-based KDFs in SP 800-108. In this paper, we examine the difference of security models between the KDFs and the encryption modes of operations. Moreover we focus on the provable security of PRF-based KDFs according to input types of counters, and show that the counter and feedback modes of KDFs using XOR of counters are insecure, while these modes using concatenation of counters are secure.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.4
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• pp.789-801
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• 2018

Currently widely used IP cameras provide the ability to control IP cameras remotely via mobile devices. To do so, the IP camera software is installed on the website specified by the camera manufacturer, and authentication is performed through the password between the IP camera and the mobile device. However, many products currently used do not provide a secure channel between the IP camera and the mobile device, so that all IDs and passwords transmitted between the two parties are exposed. To solve these problems, we propose an authentication and key exchange protocol using ID-based signature scheme. The proposed protocol is characterized in that (1) mutual authentication is performed using ID and password built in IP camera together with ID-based signature, (2) ID and password capable of specifying IP camera are not exposed, (3) provide forward-secrecy using Diffie-Hellman key exchange, and (4) provide security against external attacks as well as an honest-but-curious manufacturer with the master secret key of the ID-based signature.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.9
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• pp.702-713
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• 2003

The importance of protection for data and information is increasing by the rapid development of information communication and network. And the concern for protecting private information is also growing due to the increasing demand for lots of services by users. Asymmetric cryptosystem is the mainstream in encryption system rather than symmetric cryptosystem by above reasons. But asymmetric cryptosystem is restricted in applying fields by the reason it takes more times to process than symmetric cryptosystem. In this paper, encryption system which executes authentication works of asymmetric cryptosystem by means of symmetric cryptosystem. The proposed cryptosystem uses an algorithms combines that combines block cipherment with stream cipherment and has a high stability in aspect of secret rate by means of transition of key sequence according to the information of plaintext while symmetric/asymmetric cryptosystem conducts encipherment/deciphermeent using a fixed key. Consequently, it is very difficult to crack although unauthenticator acquires the key information. So, the proposed encryption system which has a certification function of asymmetric cryptosystem and a processing time equivalent to symmetric cryptosystems will be highly useful to authorize data or exchange important information.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.1
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• pp.3-11
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• 2009

Forward secrecy in an e-mail system means that the compromising of the long-term secret keys of the mail users and mail servers does not affect the confidentiality of the previous e-mail messages. Previous forward-secure e-mail protocols used the certified public keys of the users and thus needed PKI(Public Key Infrastructure). In this paper, we propose a password-based authenticated e-mail protocol providing forward secrecy. The proposed protocol does not require certified public keys and is sufficiently efficient to be executed on resource-restricted mobile devices.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3086-3092
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• 2014

The FTP that provides file transfer capabilities to/from another station cannot provides data confidentialities. The FTPS and SFTP can support a security functionalities. The FTPS needs a SSL layer and SFTP use a functions of SSH. And therefore the FTPS or SFTP needs an additional modules such as SSL or SSH. In this paper, we propose a new Secured FTP protocol that can support the security functions without extra security system. The Secured FTP uses Diffie-Hellman key agreement algorithm for shared secret key generation and AES-Counter algorithm for data encryption algorithm. Our designed Secured FTP is implemented in Linux environments and the proper operations of implemented Secured FTP is verified.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.7 s.349
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• pp.32-40
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• 2006

It is very important to establish a pairwise key securely in wireless sensor networks. Because sensor networks consist of devices with weak physical security, they are likely to be compromised by an attacker. However, some approaches using key pre-distribution and other approaches using one hop local keys are known to be very vulnerable to threats caused by compromised nodes, even a small number. This paper proposes a scheme where each node establishes three hop local keys and employs them for a later pairwise key establishment. When any two nodes agree a pairwise key, all nodes on the route between two nodes contribute to the agreement of the pairwise key. Here, the initial three hop local keys are employed for encrypting a secret key delivered from a node to other nodes. Therefore, the proposed scheme bothers attackers to compromise much more nodes than the scheme using one hop local keys only. The simulation results have proven that the proposed scheme provides better performance and higher security than the scheme using one hop local keys in terms of message exchange, the number of encryption and decryption, and pairwise key exposure rate.

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

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.1_2
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• pp.27-40
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• 2004

The OSGi service platform has several characteristics as in the followings. First, the service is deployed in the form of self-installable component called service bundle. Second, the service is dynamic according to its life-cycle and has interactions with other services. Third, the system resources of a home gateway are restricted. Due to these characteristics of a home gateway, there are a lot of rooms for malicious services can be Installed, and further, the nature of service can be changed. It is possible for those service bundles to influence badly on service gateways and users. However, there is no service bundle authentication mechanism considering those characteristics for the home gateway In this paper, we propose a service bundle authentication mechanism considering those characteristics for the home gateway environment. We design the mechanism for sharing a key which transports a service bundle safely in bootstrapping step that recognize and initialize equipments. And we propose the service bundle authentication mechanism based on MAC that use a shared secret created in bootstrapping step. Also we verify the safety of key sharing mechanism and service bundle authentication mechanism using a BAN Logic. This service bundle authentication mechanism Is more efficient than PKI-based service bundle authentication mechanism or RSH protocol in the service platform which has restricted resources such as storage spaces and operations.