• The Journal of the Korea Contents Association
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• v.14 no.12
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• pp.565-573
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• 2014

We have various e-commerce like on-line banking, stock trading, shopping using a PC or SmartPhone. In e-commerce, two parties use the certificate for identification and non-repudiation but, the attack on the certificate user steadily has been increasing since 2005. The most of hacking is stealing the public certificate and private key files. After hacking, the stolen public certificate and private key file is used on e-commerce to fraud. Generally, the private key file is encrypted and saved only with the user's password, and an encrypted private key file can be used after decrypted with user password. If a password is exposed to hackers, hacker decrypt the encrypted private key file, and uses it. For this reason, the hacker attacks user equipment in a various way like installing Trojan's horse to take over the user's certificate and private key file. In this paper, I propose the management method to secure private key of PKI using One Time Password certification technique. As a result, even if the encrypted private key file is exposed outside, the user's private key is kept safely.

• The Journal of the Korea Contents Association
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• v.15 no.10
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• pp.607-615
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• 2015

Mosts user of internet and smart phone has certificate, and uses it when money transfer, stock trading, on-line shopping, etc. Mosts user stores certificate in a hard disk drive of PC, or the external storage medium. In particular, the certification agencies are encouraged for user to store certificate in external storage media such as USB memory rather than a hard disk drive. User think that the external storage medium is safe, but when it is connect to a PC, certificate may be copied easily, and can be exposed to hackers through malware or pharming site. Moreover, if a hacker knows the user's password, he can use user's certificate without restrictions. In this paper, we suggest secure management scheme of the private key file using a password of the encrypted private key file, and a USB Memory's hardware information. The private key file is protected safely even if the encrypted private key file is copied or exposed by a hacker. Also, if the password of the private key file is exposed, USB Memory's container ID, additional authentication factor keeps the private key file safe. Therefore, suggested scheme can improve the security of the external storage media for certificate.

• The Journal of the Korea Contents Association
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• v.16 no.8
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• pp.90-96
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• 2016

The 3390 million people, around 83% of the adult population in Korea use smartphone. Although the safety problem of the certificate has been occurred continuously, most of these users use the certificate. These safety issues as a solution to 'The owner of a mobile phone using SMS authentication technology', 'Biometric authentication', etc are being proposed. but, a secure and reliable authentication scheme has not been proposed for replace the certificate yet. and there are many attacks to steal the certificate and private key. For these reasons, security experts recommend to store the certificate and private key on usb flash drive, security tokens, smartphone. but smartphones are easily infected malware, an attacker can steal certificate and private key by malicious code. If an attacker snatchs the certificate, the private key file, and the password for the private key password, he can always act as valid user. In this paper, we proposed a safe way to keep the private key on smartphone using smartphone's unique information and user password. If an attacker knows the user password, the certificate and the private key, he can not know the smart phone's unique information, so it is impossible to use the encrypted private key. Therefore smartphone user use IT service safely.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.4
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• pp.35-41
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• 2017

This paper introduces a new method for storing a private key. This method can be achieved by dividing the private key into "n" pieces by a (k, n) secret sharing method, and then storing each piece into photo files utilizing a steganography method. In this way, a user can restore a private key as long as he can remember the locations of "k" photos among the entire photo files. Attackers, meanwhile, will find it extremely difficult to extract the private key if a user has hidden the pieces of the private key into numerous photo files stored in the system. It also provides a high degree of user convenience, as the user can restore the private key from his memory of k positions among n photo files. Coupled with this, a certain level of security can be guaranteed because the attacker cannot restore a private key, even if he knows k-1 photo file locations.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.1
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• pp.31-40
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• 2014

In Korea, the Public Key Infrastructure (PKI) has been introduced. For secure information transmission and identification, the electronic signature authorization system of a certificate-based is built, and then the service provide.The certificate is stored in location what users can easily access and copy. Thus, there is a risk that can be stolen by malware or web account hacking. In addition, private key passwords can be exposed by the logging tool, after keyboard security features are disabled. Each of these security weaknesses is a potential conduit for identity theft, property/asset theft, and theft of the actual certificates. The present study proposes a method to prevent the private key file access illegally. When a certificate is stored, the private key is encrypted by the dependent element of the device, and it is stored securely. If private key leakage occurs, the retrieved key could not be used on other devices.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.5
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• pp.781-793
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• 2014

A Public Key Infrastructure (PKI) is security standards to manage and use public key cryptosystem. A PKI is used to provide digital signature, authentication, public key encryption functionality on insecure channel, such as E-banking and E-commerce on Internet. A soft-token private key in PKI is leaked easily because it is stored in a file at standardized location. Also it is vulnerable to a brute-force password attack as is protected by password-based encryption. In this paper, we proposed a new method that detects private key compromise and is probabilistically secure against a brute-force password attack though soft-token private key is leaked. The main idea of the proposed method is to use a genuine signature key pair and (n-1) fake signature key pairs to make an attacker difficult to generate a valid signature with probability 1/n even if the attacker found the correct password. The proposed method provides detection and notification functionality when an attacker make an attempt at authentication, and enhances the security of soft-token private key without the additional cost of construction of infrastructure thereby extending the function of the existing PKI and SSL/TLS.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.4
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• pp.103-109
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• 2008

Many Internet application provide the PKI(public key infrastructure)-based service to provide authentication and message integrity. Several researchers proposed PKI-based p2p network framework. However, in the real world, the use of PKI is not suitable for peer to peer network, because the peer-to-peer network is an open and dynamic network. Moreover, currently there is no nation-to-nation interoperable certificate. In this paper, we designed reliable p2p file sharing application without public key infrastructure. To do this we propose reliable public key distribution mechanism to distribute public key safely without PKI infrastructure for two-tier super-peer architecture. In our system, each peer generates and distributes its public/private key pairs, and the public key is securely distributed without PKI. The proposed mechanism is safe against MITM attack. This mechanism can be applied various P2P applications such as file sharing, IPTV, distributed resource sharing and so on

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.359-362
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• 2009

Qualified certificates in online financial and security transaction area are currently used for authentication of the user. The authorized user's public key certificates are stored in binary; the private key corresponding to the user's public key certificates is encrypted by the user password, and then is stored in a file. But the present management system to access the public certificates in local has some problems. In this study, we propose that the mobile public certificate management application to avoid the exist problems.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.1
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• pp.41-55
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• 2007

The certificate is used to confirm and prove the user's identity in online finance and stocks business. A user's public key is stored in the certificate(for e.g., SignCert.der) and the private key, corresponding to public key, is stored in the private key file(for e.g., SignPri.key) after encryption using the password that he/she created for security. In this paper, we show that the certificate, deleted by the commercial certificate software, can be recovered without limitation using the commercial forensic tools. In addition, we explain the problem that the private key encryption password can be detected using the SignCert.der and the SignPri.key in off-line and propose the countermeasure about the problem.

• Journal of Korea Multimedia Society
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• v.12 no.12
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• pp.1701-1709
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• 2009

The mobile terminal system plays a key role in medical industries which require in fast and accurate diagnosis from heterogeneous acquisition equipment. The demand for PACS (picture archiving and communication systems) has continued to increase in major hospitals and private clinics. Patient care depends on how fast the medical imaging system provides images and how accurately the images are interpreted by physicians. In this paper, we propose an efficient method to decipher the hundreds of images required by physicians to accurately diagnose patients. By exploring Motion- JPEG (M-JPEG), this paper has demonstrates the possibilities for efficient management of medical images with a newly designed image file format and improvement in imaging diagnoses through the replaying of moving pictures of a patient in a mobile environment.