• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4604-4623
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• 2014

Authentication mechanisms coupled with strong encryption techniques are used for network security purposes; however, given sufficient time, well-equipped intruders are successful for compromising system security. The authentication protocols often fail when they are analysed critically. Formal approaches have emerged to analyse protocol failures. In this study, Communicating Sequential Processes (CSP) which is an abstract language designed especially for the description of communication patterns is employed. Rank functions are also used for verification and analysis which are helpful to establish that some critical information is not available to the intruder. In order to establish this, by assigning a value or rank to each critical information, it is shown that all the critical information that can be generated within the network have a particular characterizing property. This paper presents an application of rank functions approach to an authentication protocol that combines delaying the decryption process with timed authentication while keys are dynamically renewed under pseudo-secure situations. The analysis and verification of authentication properties and results are presented and discussed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.312-313
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• 2017

Internet of Things(IoT) is an intelligent technology and service in which all objects communicate with each other through various networks. Recently Internet of Things(IoT) is one of the fields that is attracting attention as the development of ICT industry. MQTT is a protocol which is safe using TLS or adopting light packet structure for effciency of memory and power using. In this paper, when TLS is used the process of encryption / decryption in the broker occurs. We propose an efficient MQTT protocol through centralized key management by adding authentication server.

• The KIPS Transactions:PartC
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• v.10C no.7
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• pp.929-936
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• 2003

We Propose the Suity Cryptography File System to encrypt or decrypt a plaintext or an encrypted tort by using the dynamic linking mechanism In the Linux kernel. The dynamic linking mechanism gives the flexibility of the kernel without changing the kernel. The Sorority Cryptography File System uses the blowfish algorithm to encrypt or decrypt a data. To overcome the overhead of the key server, I use key generating algorithm which is installed in the same Security Cryptography File System. The Security Cryptography file System is fitted into the Linux system.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.3
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• pp.119-128
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• 2002

In case certification between user and service provider is achieved, problem that user's identity is revealed is occurring by social issue, so it was presented identity escrow scheme to solve these problem. In identity escrow scheme, the issuer who have correct user's identity transmits securely anonymity authentication information to user, and user achieves authentication phase with service provider keeping oneself anonymity using this. In this paper, we present requirement for security and trusty of identity escrow scheme and propose new mechanism that can security this. Also, propose method that service provider can deliver securely contents to user and propose mechanism that improve that support ky recovery at encryption communication that using secret key that it was generated by key agreement between users.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.5
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• pp.87-93
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• 2002

SHACAL is based on the hash standard SHA-1 used in encryption mode, as a submission to NESSIE. SHACAL uses the XOR, modular addition operation and the functions of bit-by-bit manner. These operations and functions make the differential cryptanalysis difficult, i.e, we hardly find a long differential with high probability. But, we can find short differentials with high probability. Using this fact, we discuss the security of SHACAL against the amplified boomerang attack. We find a 36-step boomerang-distinguisher and present attacks on reduced-round SHACAL with various key sizes. We can attack 39-step with 256-bit key, and 47-step with 512-bit key.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.6
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• pp.1207-1216
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• 2020

Since the server system in the cloud environments can simultaneously operate multiple OS and commonly share the memory space between users, an adversary can recover some secret information using cache side-channel attacks. In this paper, the Flush+Reload attack, a kind of cache side-channel attacks, is applied to the optimized precomputation table implementation of Korea block cipher standard ARIA. As an experimental result of attack on ARIA-128 implemented in Ubuntu environment, we show that the adversary can extract the 16 bytes last round key through Flush+Reload attack. Furthermore, the master key of ARIA can be revealed from last and first round key used in an encryption processing.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.1010-1013
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• 2007

와이브로 서비스는 고속 이동 인터넷 환경 속에서 고속으로 무선 인터넷 서비스를 제공하는 기술이다. 기존의 무선인터넷 서비스와 달리 이동성을 제공한다는 점에서 차별화를 제공한다. 이렇게 이동하는 단말에게 양질의 데이터를 안전하게 전송하기 위해서는 보안기술이 중요한 요소로 작용한다. 서비스를 제공하기 전에 단말(Mobile Station)과 RAS(Radio Access Stations)간의 인증을 바탕으로 상호 키(TEK:Traffic Encryption Key)를 분배하고 TEK를 바탕으로 데이터를 암호화해서 전송하게 된다. 기존의 인증 프로토콜에서는 RAS에서 단독으로 키를 생성하는 방식이지만, 본 논문에서는 기존의 프로토콜의 문제점으로 지적된 Replay Attack에 대해 DH(Diffie-Hellman) 키 분배(Key Distribution) 방식을 적용하는 프로토콜을 제안함으로써 취약점에 대비 하였다. 이를 통해 RAS에 집중되는 키 생성에 대한 오버헤드를 단말에 분산 시킬 수 있다. 이로써 제안된 프로토콜을 사용해서 기존의 프로토콜을 사용했을 때보다 보안강도를 높일 수 있다.

• Journal of KIISE:Information Networking
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• v.37 no.1
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• pp.72-83
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• 2010

Group communication in a wireless mesh network is complicated due to dynamic intermediate mesh points, access control for communications between different administrative domains, and the absence of a centralized network controller. Especially, many-to-many multicasting in a dynamic mesh network can be modeled by a decentralized framework where several subgroup managers control their members independently and coordinate the inter-subgroup communication. In this study, we propose a topology-matching decentralized group key management scheme that allows service providers to update and deliver their group keys to valid members even if the members are located in other network domains. The group keys of multicast services are delivered in a distributed manner using the identity-based encryption scheme. Identity-based encryption facilitates the dynamic changes of the intermediate relaying nodes as well as the group members efficiently. The analysis result indicates that the proposed scheme has the advantages of low rekeying cost and storage overhead for a member and a data relaying node in many-to-many multicast environment. The proposed scheme is best suited to the settings of a large-scale dynamic mesh network where there is no central network controller and lots of service providers control the access to their group communications independently.

• Journal of IKEEE
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• v.26 no.4
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• pp.736-741
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• 2022

Lattice-based cryptography is the most practical post-quantum cryptography because it enjoys strong worst-case security, relatively efficient implementation, and simplicity. Ring learning with errors (R-LWE) is a public key encryption (PKE) method of lattice-based encryption (LBC), and the most important operation of R-LWE is the modular polynomial multiplication of rings. This paper proposes a method for optimizing modular multipliers based on approximate computing (AC) technology, targeting the medium-security parameter set of the R-LWE cryptosystem. First, as a simple way to implement complex logic, LUT is used to omit some of the approximate multiplication operations, and the 2's complement method is used to calculate the number of bits whose value is 1 when converting the value of the input data to binary. We propose a total of two methods to reduce the number of required adders by minimizing them. The proposed LUT-based modular multiplier reduced both speed and area by 9% compared to the existing R-LWE modular multiplier, and the modular multiplier using the 2's complement method reduced the area by 40% and improved the speed by 2%. appear. Finally, the area of the optimized modular multiplier with both of these methods applied was reduced by up to 43% compared to the previous one, and the speed was reduced by up to 10%.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.6 s.336
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• pp.31-38
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• 2005

In this paper, we proposed an optical security system based on a gray-image exclusive-OR encryption using multi-phase separation and phase-wrapping method. For encryption, a gray image is sliced into binary images, which have the same pixel value, and these images are encrypted by modified XOR rules with binary random images. The XORed images and the binary images respectively combined and converted into full phase images, called an encrypted image and a key image. For decryption, when the encrypted image and key image are used as inputs on optical elements, Practically due to limited controllability of phase range in optical elements, the original gray image cannot be efficiently reconstructed by these optical elements. Therefore, by decreasing the phase ranges of the encrypted image and key image using a phase-wrapping method and separating these images into low-level phase images using multi-phase separation, the gray image can be reconstructed by optical elements which have limited control range. The decrytion process is simply implemented by interfering a multiplication result of encrypted image and key image with reference light. The validity of proposed scheme is verified and the effects, which are caused by phase limitation in decryption process, is analyzed by using computer simulations.