• The Transactions of the Korea Information Processing Society
• /
• v.5 no.9
• /
• pp.2256-2270
• /
• 1998

The development of a high perfoffilance index system is crucial for the retrieval of information from large sets o[ data. In this study, a minimal perfect hash function (MPHF), which hashes m keys to m buckets with no collisions, is revisited. The MOS algorithm developed bv Heath is modified to be successful for computing MPHFs of large sets of keys Also, a system for generating MPHFs for large sets of keys is developed. This system computed MPHFs for several large sets of data more efficiently than Heath's. The application areas for this system include those for generating MPHFs for the indexing of large and infrequently changing sets of data as well as information stored in a medium whose seek time is very slow.

• Journal of Arbitration Studies
• /
• v.9 no.1
• /
• pp.367-390
• /
• 1999

The basic requirements for conducting electronic commerce include confidentiality, integrity, authentication and authorization. Cryptographic algorithms, make possible use of powerful authentication and encryption methods. Cryptographic techniques offer essential types of services for electronic commerce : authentication, non-repudiation. The oldest form of key-based cryptography is called secret-key or symmetric encryption. Public-key systems offer some advantages. The public key pair can be rapidly distributed. We don't have to send a copy of your public key to all the respondents. Fast cryptographic algorithms for generating message digests are known as one-way hash function. In order to use public-key cryptography, we need to generate a public key and a private key. We could use e-mail to send public key to all the correspondents. A better, trusted way of distributing public keys is to use a certification authority. A certification authority will accept our public key, along with some proof of identity, and serve as a repository of digital certificates. The digital certificate acts like an electronic driver's license. The Korea government is trying to set up the Public Key Infrastructure for certificate authorities. Both governments and the international business community must involve archiving keys with trusted third parties within a key management infrastructure. The archived keys would be managed, secured by governments under due process of law and strict accountability. It is important that all the nations continue efforts to develop an escrowed key in frastructure based on voluntary use and international standards and agreements.

• Journal of Advanced Marine Engineering and Technology
• /
• v.32 no.6
• /
• pp.955-963
• /
• 2008

In this paper, we propose an improved practical encryption and fault-tolerance decryption method using a non-negative value key and random function obtained with a white noise by using iterative phase wrapping method. A phase wrapping operating key, which is generated by the product of arbitrary random phase images and an original phase image. is zero-padded and Fourier transformed. Fourier operating key is then obtained by taking the real-valued data from this Fourier transformed image. Also the random phase wrapping operating key is made from these arbitrary random phase images and the same iterative phase wrapping method. We obtain a Fourier random operating key through the same method in the encryption process. For practical transmission of encryption and decryption keys via Internet, these keys should be intensity maps with non-negative values. The encryption key and the decryption key to meet this requirement are generated by the addition of the absolute of its minimum value to each of Fourier keys, respectively. The decryption based on 2-f setup with spatial filter is simply performed by the inverse Fourier transform of the multiplication between the encryption key and the decryption key and also can be used as a current spatial light modulator technology by phase encoding of the non-negative values. Computer simulations show the validity of the encryption method and the robust decryption system in the proposed technique.

• Journal of Digital Convergence
• /
• v.10 no.10
• /
• pp.325-332
• /
• 2012

Due to its communication vulnerability resulting in a range of problems, e.g. eavesdropping, information exposure, traffic analysis and spoofing, RFID system becomes the target of attackers. Accordingly, many investigators have proposed various protocols to the extent of theorem proving or verification as the implementation is challenging. This paper thus proposes a safe RFID security protocol using public keys, session keys, hashes, XORs, and random numbers. Timestamps and hashes are applied to the most vulnerable section between readers and tags to detect attacks in attack signals with time difference. Also, to prevent tag information from being exposed in the last session, hash operation is adopted before communication. Finally, in this paper, we designed a RFID security protocol using public and session keys applicable to real systems and verified the security of the proposed protocol with a differentiated formal verification technique.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.17 no.2
• /
• pp.1-9
• /
• 1980

A voltage synthesizing channel selection circuit was designed to improve on the conventional vol tape synthesizer which has been memorized each charnel's tuning vol cage itself. In the course of this study, tuning voltage was calculated by channel number entered from 10 keys. Then this circuit has tie function of direct access channel selection and rear display of channel number for the whole range of UHF and VHF, Attention was also given to realize the fine tuning by searching each commended channel, and the sequential selection by using 2keys, and the flash of channel indicator in case of inactive station.

• Journal of Korea Multimedia Society
• /
• v.20 no.5
• /
• pp.782-790
• /
• 2017

As most of the recent smart devices have NFC function the NFC mobile coupon will become one of the pervasive NFC applications. We need the secure NFC coupon protocols to issue and use NFC mobile coupon. In this paper, we analyze the security of the previous protocols and point out the problems of security. As the result of analysis, Premium M-coupon Protocol proposed by A. Alshehri and S. Schneider is the most secure but has unnecessary operations. We propose the Modified Premium M-coupon Protocol-1 with the unnecessary operations removed and show this protocol is secure by security analysis. Most of NFC mobile coupon protocols use the cryptography with the shared secret keys. We propose the Modified Premium M-coupon Protocol-2 without the shared secret keys and show this protocol is secure by security analysis.

• Journal of Korea Society of Industrial Information Systems
• /
• v.27 no.2
• /
• pp.45-51
• /
• 2022

In this paper, an universal reduced input system that can represent Korean text message, English alphabet letter, special characters, and numbers is develpoed. The reduced keyboard input system has 5 number keys and 4 special function keys to reduce the complexity of inserting characters for the severely disabled. Also, mobile application is developed for the use of easy communication for the disabled.

• Journal of applied mathematics & informatics
• /
• v.6 no.3
• /
• pp.885-899
• /
• 1999

We propose a new hash function-SMD(Strengthened Mes-sage Digest) based on the design principle of dedicated hash functions. It processes an arbitrary finite message by 512-bit block and outputs 160 bits digest and has data-dependent rotation characteristic which guar-anteens the strength against existing known attacks. Moreover we also propose a new keyed MAC(Message Authentication Code) constructed by using the proposed hash function. The proposed MAC uses a max-imum keys of 160 bits and hs an output-length less than equal to the hash result. From the viewpoint of performance the proposed MAC is only reduced about 10% comparing to the underlying hash function.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.7C
• /
• pp.1015-1023
• /
• 2004

In order to protect an exchanged data, it is indispensable to establish a peer-to-peer key between the two communicating nodes. Pre-distributing keys among the nodes is unrealistic in Ad-Hoc network environment because of the dynamic nature of its network topology and the equal authority of its nodes. This paper presents a peer-to-peer key establishment scheme without pre-distributing keys in Ad-Hoc networks. The proposed scheme is based on the Diffie-Hellman key exchange protocol. Main idea is to prevent the falsification of Diffe-Hellman values using some elements of a hash chain. As a result, it is as safe as the underlying hash function against a man-in-the-middle attack. Simulation results have shown that the proposed scheme dramatically reduces the number of messages, and has relatively higher scalability, as compared with the key pre-distribution based scheme.

• The Korea Journal of Herbology
• /
• v.30 no.4
• /
• pp.65-69
• /
• 2015

Objectives : The root ofCyanchum wifordii(CW) had been used as herbal medicine, 'Baeksuo', in Korea. However, the root ofCynanchum auriculatum(CA) had also been mis-used as 'Baeksuo' in herbal markets, due to its morphological similarity with CW. This study aimed to compare discriminative features and establish the identification-keys between two herbal medicines using microscopic methods.Methods : Microscopic preparations including fixation, rapid dehydration, paraffin infiltration, paraffin embedding, sectioning, mounting, and staining, were performed and the microscopic features between CW and CA samples were compared.Results : The starch grain of parenchymal cells, the amounts of calcium oxalate crystals, cell sizes, and the shape of phloem were not different between CW and CA samples. However, the clusters of stone cells which were conglomerated at outer cortex were apparently observed in CA sample (4~8 layers of stone cells), but not in CW sample (2~4 layers of stone cells, or not). Xylem of CW consisted of several vessels and fiber bundles which were formed as linear shapes and discontinuous radial lines, while that of CA, in which radial lines was not observed, were shaped as a wedge and scattered near cambium with comparatively few fiber bundles enclosed vessels. Especially, in the xylem of CA, fiber bundles located towards cambium were relatively more developed than those located outward cambium.Conclusions : The identification-keys established in this study would be helpful to discriminate microscopic features between CW and CA.