• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.1
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• pp.53-62
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• 2009

H. Gilbert et al. proposed a collision attack on 7-round reduced Rijndael[5]. Applying this attack, we propose collision attacks on 8-round reduced Crypton, 8-round reduced mCrypton in this paper. Attacks on Crypton requires $2^{161.6}$ time complexity with $2^{96}$ chosen plaintexts, respectively. The attack on mCrypton requires $2^{81.6}$ time complexity with $2^{48}$ chosen plaintexts. These results are the best attacks on Crypton and mCrypton in published literatures.

• Journal of Internet of Things and Convergence
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• v.6 no.2
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• pp.93-100
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• 2020

Although various home services are developed as increasing the number of home devices with wire and wireless connection, privacy infringement and private information leakage are occurred by unauthorized remote connection. It is almost caused by without of device authentication and protection of transmission data. In this paper, the devices' secret value are stored in a safe memory of a smartphone. A smartphone processes device authentication. In order to prevent leakage of a device's password, a shadow password multiplied a password by the private key is stored in a device. It is proposed mutual authentication between a smartphone and a device, and session key agreement for devices using recovered passwords on SRP. The proposed protocol is resistant to eavesdropping, a reply attack, impersonation attack.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.3
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• pp.251-255
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• 2008

In most file systems, if a file is deleted, only the metadata of the file is deleted or modified and the file's data is still stored on the physical media. Some users require that deleted files no longer be accessible. This requirement is more important in embedded systems that employ flash memory as a storage medium. In this paper, we propose a secure deletion method for NAND flash file system and apply the method to YAFFS. Our method uses encryption to delete files and forces all keys of a specific file to be stored in the same block. Therefore, only one erase operation is required to securely delete a file. Our simulation results show that the amortized number of block erases is smaller than the simple encryption method. Even though we apply our method only to the YAFFS, our method can be easily applied to other NAND flash file systems.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.33 no.3
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• pp.363-374
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• 2023

A white-box environment refers to a situation where the internal information of an algorithm is disclosed. The AES white-box encryption was first announced in 2002, and in 2016, a side-channel analysis for white-box encryption called Differential Computation Analysis (DCA) was proposed. DCA analysis is a powerful side-channel attack technique that uses the memory information of white-box encryption as side-channel information to find the key. Although various countermeasure studies against DCA have been published domestically and internationally, there were no evaluated or analyzed results from experiments applying the hiding technique using dummy operations to DCA analysis. Therefore, in this paper, we insert LU T-shaped dummy operations into the WBC-AES algorithm proposed by S. Chow in 2002 and quantitatively evaluate the degree of change in DCA analysis response depending on the size of the dummy. Compared to the DCA analysis proposed in 2016, which recovers a total of 16 bytes of the key, the countermeasure proposed in this paper was unable to recover up to 11 bytes of the key as the size of the dummy decreased, resulting in a maximum decrease in attack performance of about 68.8%, which is about 31.2% lower than the existing attack performance. The countermeasure proposed in this paper confirms that the attack performance significantly decreases as smaller dummy sizes are inserted and can be applied in various fields.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.6
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• pp.1117-1127
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• 2014

Differential Fault Analysis(DFA) is widely known for one of the most powerful method for analyzing block cipher. it is applicable to block cipher such as DES, AES, ARIA, SEED, and lightweight block cipher such as PRESENT, HIGHT. In this paper, we introduce a differential fault analysis on the lightweight block cipher LEA for the first time. we use 300 chosen fault injection ciphertexts to recover 128-bit master key. As a result of our attack, we found a full master key within an average of 40 minutes on a standard PC environment.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.12
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• pp.569-576
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• 2013

Cloud computing has been receiving increasing attention recently. Despite this attention, security is the main problem that still needs to be addressed for cloud computing. In general, a cloud computing environment protects data by using distributed servers for data storage. When the amount of data is too high, however, different pieces of a secret key (if used) may be divided among hundreds of distributed servers. Thus, the management of a distributed server may be very difficult simply in terms of its authentication, encryption, and decryption processes, which incur vast overheads. In this paper, we proposed a efficiently data storage and recovery scheme using XOR and RAID in Hadoop environment.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.3
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• pp.53-64
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• 2005

In this paper, proposes Kerberos certification mechanism that improve certification service of PKINIT base that announce in IETF CAT Working Croup. Also proposed Authentication Mechanism for reusability of Ticket that after Ticket's Lifetime is ended, message exchange that Local Client receives Remote Server's service. Since my suggestion to regional services are not described in Kerberos, authentication between regions can be performed via PKINIT(Public Key Cryptography for Initial Authentication) presented by IETF(Internet Engineering Task Force) CAT working group. The new protocol is better than the authentication mechanism proposed by IETF CAT Working group in terms of communication complexity and mechanism according to simplified Ticket issue processing.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.5
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• pp.167-174
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• 2009

Recently, Li et al. proposed a new differential fault analysis(DFA) attack on the block cipher ARIA using about 45 ciphertexts. In this paper, we apply their DFA skill on AES and improve attack method and its analysis. The basic idea of our DFA method is that we recover intermediate ciphertexts in last round using final faulty ciphertexts and find out last round secret key. In addition, we present detail DFA procedure on AES and analysis of complexity. Furthermore computer simulation result shows that we can recover its 128-bit secret key by introducing a correct ciphertext and 2 faulty ciphertexts.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.33 no.4
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• pp.591-599
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• 2023

Due to the recent attack by Castryck-Decru, the private key of SIDH can be recovered in polynomial time so several methods have been proposed to prevent the attack. Among them, M-SIDH proposed by Fouotsa et al, counteracts the attack by masking the torsion point information during the key exchange. In this paper, we implement M-SIDH and evaluate its performance. To the best of our knowledge, this is the first implementation of M-SIDH in C language. Toward that end, we propose a method to select parameters for M-SIDH instantiation and propose a 1024-bit prime for implementation. We implemented the square-root Velu formula over the extension field for further optimization. As a result, 1129 ms is required for a key exchange in the case of MSIDH-1024, providing the classic 64-bit security level.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.6
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• pp.21-26
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• 2023

Recently, cryptocurrencies such as Ethereum and Bitcoin, which are called digital assets, Cryptocurrency has completely different characteristics from real assets and must be handled carefully and safely. But The disadvantage of digital assets is that anyone who knows the private key of the wallet can easily steal the digital assets. If the seed card is lost, stolen, or exposed when used, you can use the wallet by recovering the private key using the seed card acquired by someone else. In this paper We aim to safely protect encrypted assets by using QR codes when providing mnemonic words needed to create seed cards.