• The Journal of Information Technology
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• v.9 no.4
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• pp.49-55
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• 2006

In this paper, a new fragile watermarking algorithm for digital image is presented, which makes resolving the security and forgery problem of the digital image to be possible. The most suitable watermarking method that verifies the authentication and integrity of the digital image is the Wong's method, which invokes the hash function (MD5). The algorithm is safe because this method uses the hash function of the cryptology. The operations such as modulus, complement, shift, bitwise exclusive-or, bitwise inclusive-or are necessary for calculating the value of hash function. But, in this paper, an Arithmetic encoding method that only includes the multiplication operation is adopted. This technique prints out accumulative probability interval, which is obtained by multiplying the input symbol probability interval. In this paper, the initial probability interval is determined according to the value of the key, and the input sequence of the symbols is adjusted according to the key value so that the accumulative probability interval will depend on the key value. The integrity of the algorithm has been verified by experiment. The PSNR is above the 51.13db and the verifying time is $1/3{\sim}1/4$ of the verifying time of using the hash function (MD5), so, it can be used in the real-time system.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.951-954
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• 2002

This paper presents the implementation of hash functions for IPSEC chip. There is an increasing interest in high-speed cryptographic accelerators for IPSec applications such as VPNs (virtual private networks). Because diverse algorithms are used in Internet, various hash algorithms are required for IPSec chip. Therefore, we implemented SHA-1, HAS-160 and MD5 in one chip. These hash algorithms are designed to reduce the number of gates. SHA-1 module is combined with HAS-160 module. As the result, the required logic elements are reduced by 27%. These hash algorithms have been implemented using Altera's EP20K1000EBC652-3 with PCI bus interface.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.1
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• pp.31-39
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• 2016

Hash function is a cryptographic primitive which conduct authentication, signature and data integrity. Recently, Wang et al. found collision of standard hash function such as MD5, SHA-1. For that reason, National Security Research Institute in Korea suggests a secure structure and efficient hash function, LSH. LSH consists of three steps, initialization, compression, finalization and computes hash value using addition in modulo $2^W$, bit-wise substitution, word-wise substitution and bit-wise XOR. These operation is parallelizable because each step is independently conducted at the same time. In this paper, we analyse LSH structure and implement it over SIMD-SSE, AVX and demonstrate the superiority of LSH.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.4
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• pp.55-66
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• 2002

HAVAL is a dedicated hash function of the MD family which was proposed by Zheng et al.. HAVAL compresses a message of arbitrary length into a hash value of 128, 160, 192, 224, or 256 bits. HAVAL has a parameter that controls the number of passes a message block of 1024 bits is processed. A message block can be processed in 3,4, or 5 passes. When a message block is processed in three passes, we call such a case 3-pass HAVAL. So, there are three kinds of HAVAL: 3-pass HAVAL, 4-pass HAVAL, and 5-pass HAVAL. In this paper, we study the security of reduced versions of 3-pass HAVAL. We propose a method for finding the collisions for the first two passes of 3-pass HAVAL and for the last two passes of 3-pass HAVAL. This approach of reducing the number of passes is similar to the initial attacks on MD4. We represent the first two passes of 3-pass HAVAL as HAVAL-12 and the last two passes of 3-pass HAVAL as HAVAL-23.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06d
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• pp.260-261
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• 2012

스마트 환경에 관심이 높아지면서 무선 센서 네트워크를 이용한 유비쿼터스 시스템을 실생활에 활용하려는 노력이 이어지고 있다. 무선 센서 네트워크는 무선 통신으로 정보를 수집하기 때문에 실생활에 적용할 경우 사생활 정보가 유출될 가능성을 가진다. 본 논문은 데이터 전송 과정에서 데이터가 유출되었을 때, 원본 데이터로의 해독을 어렵게 하는 해시 알고리즘을 제안한다. 제안하는 알고리즘은 단 방향 해시 함수인 MD5를 변형한 TinyMD5를 이용하여 데이터를 변환하고, MD5를 변형하면서 발생하는 해시 값 충돌 문제를 해결할 수 있는 기법을 추가하였다. 제안하는 알고리즘의 우수성을 보이기 위해 기존의 기법과 시뮬레이션을 통해 성능을 비교 평가하였다. 성능 평가 결과, 제안하는 알고리즘은 통신 에너지를 기존 알고리즘의 평균 29%만을 소모하였다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.21 no.5
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• pp.27-33
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• 2011

At FDTC'05 and CISC-W'10, the authors showed that if they decrease the number of rounds of AES and Triple-DES by using the fault injections, it is possible to recover the secret key of the target algorithms, respectively. In this paper, we propose a key recovery attack on HMAC by using the main idea of these attacks. This attack is applicable to HMAC based on MD-family hash functions and can recover the secret key with the negligible computational complexity. Particularly, the attack result on HMAC-SHA-2 is the first known key recovery attack result on this algorithm.

• The Journal of the Korea Contents Association
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• v.12 no.1
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• pp.48-58
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• 2012

With the development of sensing devices and wireless communication technologies, wireless sensor networks are composed of a large number of sensor nodes that are equipped with limited computing performance and restricted communication capabilities. Besides, the sensor nodes are deployed in hostile or unattended environments. Therefore, the wireless sensor networks are vulnerable to security. In particular, the fatal damage may be occurred when data are exposed in real world applications. Therefore, it is important for design requirements to be made so that wireless sensor networks provide the strong security. However, because the conventional security schemes in wired networks did not consider the limited performance of the sensor node, they are so hard to be applied to wireless sensor networks. In this paper, we propose a secure multipath transmission scheme based on one-way hash functions in wireless sensor networks considering the limited performance of the wireless sensor nodes. The proposed scheme converts a sensor reading based on one of one-way hash functions MD5 in order to make it harder to be cracked and snooped. And then, our scheme splits the converted data and transfers the split data to the base station using multi-path routing. The experimental results show that our proposed scheme consumes the energy of just about 6% over the existing security scheme.

• Journal of Digital Forensics
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• v.12 no.3
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• pp.97-108
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• 2018

Computer technology and Internet advances enable easy massive file transfer by messenger, email, and web hard service users this means that a child pornography file owner who is illegally possessing itself can quickly transfer that to other users However there are currently no specific ways to prevent or block the distribution of child pornography between messenger, email, and web hard service users. in this paper, we propose a method to prevent the distribution of child pornography using the MD5, SHA-1 hash value stored in the 'police Child pornography Profiling system' and to identify the child pornography suspects using the subscriber information. the user extracts the hash value of the file before distributing the file, compared it with police system, and if it has the same value, blocks the transmission of the file and sends warning to the owner. the service provider sends the subscriber information to investigation agency child pornography owners can conduct a quick and accurate investigation.

• Journal of Korea Multimedia Society
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• v.24 no.1
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• pp.58-66
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• 2021

The user's password must be encrypted one-way through the hash function and stored in the database. Widely used hash functions such as MD5 and SHA-1 have also been found to have vulnerabilities, and hash functions that are considered safe can also have vulnerabilities over time. Salt enhances password security by adding it before or after the password before putting it to the hash function. In the case of the existing Salt, even if it is randomly assigned to each user, once it is assigned, it is a fixed value in a specific column of the database. If the database is exposed to an attacker, it poses a great threat to password cracking. In this paper, we suggest variable-dynamic Salt that dynamically changes according to the user's password during the login process. The variable-dynamic Salt can further enhance password security during login process by making it difficult to know what the Salt is, even if the database or source code is exposed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.8
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• pp.1977-1985
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• 2009

An e-Seal is an active RFID device that was set on the door of a container. e-Seal provides both the state of the seal and the remote control of the device automatically. But it has vulnerabilities like eavesdrop and impersonate because of using RFID system. A secure e-Seal authentication protocol must use PRF for encryption/decryption of reader and e-Seal. The existing PRF uses simple hash function such as MD5 or SHA which is not available for e-Seal. It is required to use strong hash functions. The hash function is a essential technique used for data integrity, message authentication and encryption in the mechanism of information security. Therefore, in this paper, we propose more secure and effective hash function based on polynomial for e-Seal authentication protocol.