• Journal of Information Processing Systems
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• 제6권4호
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• pp.453-480
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• 2010

Cryptographic hash functions reduce inputs of arbitrary or very large length to a short string of fixed length. All hash function designs start from a compression function with fixed length inputs. The compression function itself is designed from scratch, or derived from a block cipher or a permutation. The most common procedure to extend the domain of a compression function in order to obtain a hash function is a simple linear iteration; however, some variants use multiple iterations or a tree structure that allows for parallelism. This paper presents a survey of 17 extenders in the literature. It considers the natural question whether these preserve the security properties of the compression function, and more in particular collision resistance, second preimage resistance, preimage resistance and the pseudo-random oracle property.

• 한국멀티미디어학회논문지
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• 제10권12호
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• pp.1663-1670
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• 2007

One-way hash chains are important cryptographic primitives and have been used as building blocks of various cryptographic applications. Advantages of one-way hash chains are their simplicity and efficiency for generation based on low-powered processors with short time. However, a drawback of one-way hash chains is their difficulty of control to compute interval values of one-way hash chains. That is, when hash values in one-way hash chain are used as encryption keys, if one hash value is compromised, then the attacker can compute other encryption keys from the compromised hash value. Therefore, direct use of one-way hash chains as encryption keys is limited to many cryptographic applications, such as pay per view system and DRM system. In this paper, we propose a new concept which is called interval hash chain using a hash function. In particular, proposed hash chains are made for only computing interval hash values by using two different one-way hash chains. The proposed scheme can be applied to contents encryption scheme for grading and partially usable contents in DRM system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권12호
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• pp.6161-6176
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• 2018

Pseudorandom numbers are useful in cryptographic operations for using as nonce, initial vector, secret key, etc. Security of the cryptosystem relies on the secret key parameters, so a good pseudorandom number is needed. In this paper, we have proposed a new approach for generation of pseudorandom number. This method uses the three dimensional combinational puzzle Rubik Cube for generation of random numbers. The number of possible combinations of the cube approximates to 43 quintillion. The large possible combination of the cube increases the complexity of brute force attack on the generator. The generator uses cryptographic hash function. Chaotic map is being employed for increasing random behavior. The pseudorandom sequence generated can be used for cryptographic applications. The generated sequences are tested for randomness using NIST Statistical Test Suite and other testing methods. The result of the tests and analysis proves that the generated sequences are random.

• Journal of Information Processing Systems
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• 제12권2호
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• pp.310-321
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• 2016

TCS_SHA-3 is a family of four cryptographic hash functions that are covered by a United States patent (US 2009/0262925). The digest sizes are 224, 256, 384 and 512 bits. The hash functions use bijective functions in place of the standard compression functions. In this paper we describe first and second preimage attacks on the full hash functions. The second preimage attack requires negligible time and the first preimage attack requires $O(2^{36})$ time. In addition to these attacks, we also present a negligible time second preimage attack on a strengthened variant of the TCS_SHA-3. All the attacks have negligible memory requirements. To the best of our knowledge, there is no prior cryptanalysis of any member of the TCS_SHA-3 family in the literature.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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• pp.948-950
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• 2002

IPSec authentication provides support for data integrity and authentication of IP packets. Authentication is based on the use of a message authentication code(MAC). Hash function algorithm is used to produce MAC , which is referred to HMAC. In this paper, we propose a cryptographic accelerator using FPGA implementations. The accelator consists of a hash function mechanism based on MD5 algorithm, and a public-key generator based on a Elliptiv Curve algorithm with small scale of circuits. The accelator provides a messsage authentification as well as a digital signature. Implementation results show the proposed cryptographic accelerator can be applied to IPSec authentications.

• 전기전자학회논문지
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• 제22권1호
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• pp.38-45
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• 2018

ARIA, AES 블록암호와 Whirlpool 해시함수를 단일 하드웨어 구조로 통합하여 효율적으로 구현한 크립토 프로세서에 대해 기술한다. ARIA, AES, Whirlpool의 알고리듬 특성을 기반으로 치환계층과 확산계층의 하드웨어 자원이 공유되도록 설계를 최적화하였다. Whirlpool 해시의 라운드 변환과 라운드 키 확장을 위해 라운드 블록이 시분할 방식으로 동작하도록 설계하였으며, 이를 통해 하드웨어 경량화를 이루었다. ARIA-AES-Whirlpool 통합 크립토 프로세서는 Virtex5 FPGA에 구현하여 하드웨어 동작을 검증하였으며, $0.18{\mu}m$ CMOS 셀 라이브러리로 합성한 결과 68,531 GE로 구현되었다. 80 MHz 클록 주파수로 동작하는 경우에, ARIA, AES 블록암호는 각각 602~787 Mbps, 682~930 Mbps, 그리고 Whirpool 해시는 512 Mbps의 성능을 갖는 것으로 예측되었다.

• 정보과학회 논문지
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• 제41권11호
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• pp.885-891
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• 2014

해시 함수는 암호 모듈, 암호 제품에서 무결성, 인증, 전자서명 등의 기능을 제공하기 위해 필수적으로 사용되는 암호 프리미티브이다. 본 논문에서는 암호 알고리즘이 제대로 구현되었는지 평가하는 암호 알고리즘 구현 적합성 검정 프로그램(CAVP)이라는 개념과 테스트 방법을 이용하여 SHA-3로 선정된 KECCAK 알고리즘의 구현 적합성 검정 프로그램을 개발하였다. 또한 SHA-3의 구조 분석을 통해 CAVP에 맞는 SHA-3 알고리즘을 16bit-UICC상에 구현하였으며 현재 표준 해시 함수인 SHA-2 알고리즘과의 효율성 비교 분석을 수행하였다.

• 정보보호학회논문지
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• 제31권3호
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• pp.323-330
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• 2021

최근에는 양자 컴퓨터의 빠른 연산의 장점이 알려지면서 큐비트를 활용한 양자회로에 대한 관심이 높아지고 있다. 그루버 알고리즘은 n-bit의 보안 레벨의 대칭키 암호와 해시 함수를 n/2-bit 보안 레벨까지 낮출 수 있는 양자 알고리즘이다. 그루버 알고리즘은 양자 컴퓨터상에서 동작하기 때문에 적용 대상이 되는 대칭키 암호와 해시함수는 양자 회로로 구현되어야 한다. 이러한 연구 동기로, 최근 들어 대칭키 암호 또는 해시 함수를 양자 회로로 구현하는 연구들이 활발히 수행되고 있다. 하지만 현재는 큐비트의 수가 제한적인 상황으로 최소한의 큐비트 개수로 구현하는 것에 관심을 가지고 효율적인 구현을 목표로 하고 있다. 본 논문에서는 국산 해시함수 LSH 구현에 큐빗 재활용, 사전 연산을 통해 사용 큐빗 수를 줄였다. 또한, Mix, Final 함수와 같은 핵심 연산들을 IBM에서 제공하는 양자 프로그래밍 툴인 ProjectQ를 사용하여 양자회로로 효율적으로 구현하였고 이에 필요한 양자 자원들을 평가하였다.

• Asia pacific journal of information systems
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• 제30권1호
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• pp.21-30
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• 2020

Bitcoin (BTC) is a type of cryptocurrency that supports transaction/payment of virtual money between BTC users without the presence of a central authority or any third party like bank. It uses some cryptographic techniques namely public- and private-keys, digital signature and cryptographic-hash functions, and they are used for making secure transactions and maintaining distributed public ledger called blockchain. In BTC system, each transaction signed by sender is broadcasted over the P2P (Peer-to-Peer) Bitcoin network and a set of such transactions collected over a period is hashed together with the previous block/other values to form a block known as candidate block, where the first block known as genesis-block was created independently. Before a candidate block to be the part of existing blockchain (chaining of blocks), a computation-intensive hard problem needs to be solved. A number of miners try to solve it and a winner earns some BTCs as inspiration. The miners have high computing and hardware resources, and they play key roles in BTC for blockchain formation. This paper mainly analyses the underlying cryptographic techniques, identifies some weaknesses and proposes their enhancements. For these, two modifications of BTC are suggested ― (i) All BTC users must use digital certificates for their authentication and (ii) Winning miner must give signature on the compressed data of a block for authentication of public blocks/blockchain.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(1)
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• pp.297-300
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• 2004

In cellular communication, subscriber authentication is an essential technique. The mobile station should operate in conjunction with the base station to authenticate the identity. In CDMA system, authentication is the process by which information is exchanged between a mobile station and base station for the purpose of confirming the mobile station. A successful authentication process means that the mobile station and base station process identical sets of shared secret data(SSD). SSD can be generated by authentication algorithms. The cryptographic hash function is a practical way of authentication algorithms. In this paper, we propose and implement MD5 and SHA-1 with modified structure.