• Management & Information Systems Review
• /
• v.12
• /
• pp.1-15
• /
• 2003

As a rapid development of electronic commerce transactions in these days, the security and private protection problems became more important matters under the electronic transaction base. Because electronic transaction using electronic documents be carried without direct person to person meeting, there can be the possibility to use other's identity illegally without notice, and very hard to verify authenticity of transaction as well. In addition, it is very hard to find out that the electronic documents on the process of submitting is forged documents or not, and also have much difficulty in maintaining transmitting secret. Therefore, to solve such problems on electronic commerce transactions and electronic documents, the digital signature and certification system with cryptography skill is inevitably necessary. As the wide use of digital signature together with beginning of digital government and financial transaction, not only the issuance of electronic certification, but certification market came to gradually expand. In Korea, after enacting digital signature act in 1999, the act contents were expanded to the wide range of contents complying with global standards from the end of 2001 to April, 2002, including the new clause of certification problems. And the act was put into operation now. Therefore, in this paper, we'd like to suggest development scheme through the investigation on electronic certification related problems, such as, concepts, procedures, service conditions here and abroad.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.6C
• /
• pp.651-657
• /
• 2006

This paper propose the technique for the execution authentication of digital signature with TTS(traceable trust server) to guarantee the safe execution of mobile agents. That is to say, it is focused on improving the processing speed of systems and the traffic of network which are problems in the existing studies. The digital signature is used to guarantee the efficient and safe execution and the integrity of mobile agents. The certificate of it is chained with synthesis function, cryptographic algorithm based on public key, and hash function. And white hosts can be protected against the threat of being used maliciously. Then, we prove the efficiency of system overhead and the traffic of network by the analysis. In case the certificate chain of a digital signature is used, the safe execution of mobile agents can be protected against attackers that wish to insert a newly created certificate after cutting off the chain after striking space key 2 times.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.34 no.1
• /
• pp.1-9
• /
• 2024

Multivariate Quadratic (MQ)-based digital signature schemes have advantages such as ease of implementation and small signature sizes, making them promising candidates for post-quantum cryptography. To enhance the efficiency of such MQ-based digital signature schemes, utilizing sparse matrices have been proposed, including HiMQ, which has been standardized by Korean Telecommunications Technology Association standard. However, HiMQ shares a similar key structure with Rainbow, which is a representative MQ-based digital signature scheme and was broken by the MinRank attack proposed in 2022. While HiMQ was standardized by a TTA and recommended parameters were provided, these parameters were based on cryptanalysis as of 2020, without considering recent attacks. In this paper, we examine attacks applicable to MQ-based digital signatures, specifically targeting HiMQ, and perform a security analysis. The most effective attack against HiMQ is the combined attack, an improved version of the MinRank attack proposed in 2022, and none of the three recommended parameters satisfy the desired security strength. Furthermore, HiMQ-128 and HiMQ-160 do not meet the minimum security strength requirement of 128-bit security level.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.11 no.5
• /
• pp.43-52
• /
• 2001

Y. Zheng introduced a new type of cryptograghic primitive as \"signcryption\", which combines a function of digital signature scheme with a symmetric key encryption algorithm. Signcryption doesn\`t only provide authenticity and confidentiality in a single step, but also give more efficient computation than the traditional \"signature-then-encryption\". And C. Gamage proposed a proxy-signcryption that efficiently combines a proxy signature with the signcryption. But, in the proposed signcryption schemes, one who obtains the sender\`s private key can recover the original message of a signcrypted text. That is, forward secrecy is not offered by the signcryption scheme with respect to the sender\`s private key. In this paper, we will propose a modified signcryption of Zheng\`s signcryption and a variant of proxy-signcryption with forward secrecy.ith forward secrecy.

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

• The KIPS Transactions:PartC
• /
• v.14C no.6
• /
• pp.463-470
• /
• 2007

Revocation is one of the main difficulties faced in implementing Public Key Infrastructures(PHs). Boneh, Ding and Tsudik first introduced a mediated cryptography for obtaining immediate revocation of RSA keys used in PKIs. Their method is based on the idea that each user's private key can be split into two random shares, one of which is given to the user and the other to an online security mediator(SEM). Thus any signature or decryption must be performed as a cooperation between a user and his/her associated SEM and revocation is achieved by instructing the mediator SEM to stop cooperating the user. Recently, Libert and Quisquater showed that the fast revocation method using a SEcurity Mediator(SEM) in a mRSA can be applied to the Boneh-Franklin identify based encryption and GDH signature schemes. In this paper we propose a mediated identity based signature(mIBS) with batch verification which apply the SEM architecture to an identity based signature. Libert's GDH siganture scheme is not forward secure even though forward security is an important and desirable feature for signature schemes. We propose an efficient key udating mediated signature scheme, mKUS based on mIBS and analyze its security and efficiency.

• Journal of the Korea Computer Industry Society
• /
• v.5 no.8
• /
• pp.829-840
• /
• 2004

Business model in Web environments is usually provided by digital data. Information exchange of users and service providers should be performed by encryted data. Encrypted protection. In this paper, We have prevented using contents by users is not accessed based on RBAC. in this paper, We propose a new DB encryption scheme which use RBAC and digital signature based on PMI.

• Journal of applied mathematics & informatics
• /
• v.8 no.3
• /
• pp.943-957
• /
• 2001

In this paper, we propose an efficient encryption algorithm, without exchanging session keys of a symmetric cryptosystem. The proposed scheme, called as the FAKE(Fast Asymmetric Key Encryption), first scrambles an entire input message and then encrypts small parts of the scrambled message using an asymmetric key encryption scheme. We use the all-or-nothing transform based on the hash function as a scrambling function, which was proposed by Shin, et al. Furthermore, the proposed scheme can additionally provide a digital signature service with only small overhead.

• Journal of Digital Convergence
• /
• v.12 no.2
• /
• pp.243-248
• /
• 2014

The demand for messenger service goes on growing rapidly with widespread use of smartphones. Generally, the smartphone messenger provides group communication functions in which users can make the group and communicate with each other. In the mobile meeting, the attendees can participate in the meeting with use of smartphone messengers wherever they are. To make the mobile meeting put to practical use, the mobility and privacy should be ensured to attendees. To satisfy the mobility requirement, the user which is not belong to the group members should not be able to participate in the meeting. To ensure the privacy requirement, the attendees should have not to repudiate the meeting results. In this study, the mobile meeting authentication scheme is proposed which provides mobility and privacy. The proposed scheme consists of meeting group creation, group key generation, group signature and verification protocols. All attendees should have to participate in the signature verification because it is based on the challenge-response type protocol. Thus, it's not possible to collude with malicious attendees to change the meeting results.

• The Journal of the Korea Contents Association
• /
• v.1 no.1
• /
• pp.83-92
• /
• 2001

In this study, we combine information hiding technique with digital contents protection scheme. For providing secure distribution on digital contents, a new paradigm can be proposed after considering both watermarking and fingerprinting techniques. In detail, publicly verifiable digital signature schemes are applied into digital contents. On signing digital copyrights, we can publicly verify its correctness if needed.