• Journal of the Korea Institute of Information Security & Cryptology
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• v.11 no.4
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• pp.55-66
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• 2001

In this paper, we analyze the security of OFB encryption mode which is one of the basic modes of operation for the block cipher and the security of 3GPP f8 encryption mode used to provide the data confidentiality over a radio access link of W-CDMA IMT-2000. We provide the lower bound and the upper bound on security of both modes in random function model and random permutation model, respectively, by means of the left-or-right security notion, and prove the security of both modes using a pseudorandom function and a pseudorandom permutation, respectively.

• ETRI Journal
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• v.38 no.4
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• pp.724-734
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• 2016

To achieve confidentiality, integrity, authentication, and non-repudiation simultaneously, the concept of signcryption was introduced by combining encryption and a signature in a single scheme. Certificate-based encryption schemes are designed to resolve the key escrow problem of identity-based encryption, as well as to simplify the certificate management problem in traditional public key cryptosystems. In this paper, we propose a new certificate-based signcryption scheme that has been proved to be secure against adaptive chosen ciphertext attacks and existentially unforgeable against chosen-message attacks in the random oracle model. Our scheme is not based on pairing and thus is efficient and practical. Furthermore, it allows a signcrypted message to be immediately verified by the public key of the sender. This means that verification and decryption of the signcrypted message are decoupled. To the best of our knowledge, this is the first signcryption scheme without pairing to have this feature.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.11
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• pp.2928-2940
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• 2013

Key exposure is a major threat to secure cryptosystems. To mitigate the impact caused by key-compromise attacks, a key-insulated cryptographic mechanism is a better alternative. For securing the large message communication in peer-to-peer networks, in this paper, we propose the first novel identity-based key-insulated encryption (IB-KIE) scheme with message linkages. Our scheme has the properties of unbounded time periods and random-access key-updates. In the proposed scheme, each client can periodically update his private key while the corresponding public one remains unchanged. The essential security assumption of our proposed scheme is based on the well-known bilinear Diffie-Hellman problem (BDHP). To ensure the practical feasibility, we also formally prove that the proposed scheme achieves the security requirement of confidentiality against indistinguishability under adaptive chosen-ciphertext attacks (IND-CCA2) in the random oracle model.

• Journal of information and communication convergence engineering
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• v.10 no.4
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• pp.343-348
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• 2012

ZigBee Network is enabling technology for home automation, surveillance and monitoring system. For better secure network environment, secure and robust security model is important. The paper proposes an application, attribute-based proxy re-encryption on ZigBee networks. The method can distribute the authority to designated sensor nodes to decrypt re-encrypted ciphertext with associated attributes. However, a previous method is required to compute complex pairing operations. The high complexity is not suited to low resource device sensor networks, and it does not provide routing security either. To resolve these problems, we present a novel mechanism. The method can reduce overhead by imposing overhead to full function devices and ensure routing paths as well.

• Journal of information and communication convergence engineering
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• v.7 no.1
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• pp.24-29
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• 2009

Sahai and Waters first introduced the concept of Fuzzy Identity Based Encryption (FIBE) to provide an error-tolerance property for Identity Based Encryption (IBE) in 2005. Yang et al. extended this idea and introduced the concept of Fuzzy Identity Based Signature (FIBS) in 2008, and constructed a FIBS scheme based on Sahai and Waters's FIBE scheme. In this paper, we further formalize the notion and security model of FIBS scheme and propose a new construction of FIBS scheme based on bilinear pairing. The proposed FIBS scheme not only provide shorter public parameters, private key and signature, but also have useful structures which result in more efficient key extraction, signing and verification than that of Yang et al.'s FIBS scheme.

• Journal of Korea Multimedia Society
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• v.8 no.5
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• pp.679-690
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• 2005

Business model in Web environments is usually provided by multimedia data. Information exchange between users and service providers should be made in encrypted data. Encrypted data are secure from being hacked. Application of DB encryption is a main technology for contents protection. We have applied the access control based on RBAC and prevented the unauthorized users from using the contents. In this paper, we propose a new DB encryption scheme which uses RHAC and digital signature based on PMI.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.2
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• pp.428-439
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• 2011

The main challenge in building efficient broadcast systems is to encrypt messages with short ciphertexts. In this paper, we present a new construction based on the identity. Our construction contains the desirable features, such as constant size ciphertexts and private keys, short public keys and not fixing the total number of possible users in the setup. In addition, the proposed scheme achieves the full security which is stronger than the selective-identity security. Furthermore we show that the proof of security does not rely on the random oracles. To the best our knowledge, it is the first efficient scheme that is full security and achieves constant size ciphertexts and private keys which solve the trade-off between the ciphertext size and the private key size.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.9
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• pp.3401-3420
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• 2021

We provide a traceable ciphertext-policy attribute based encryption (CP-ABE) construction for monotone access structures (MAS) based on composite order bilinear groups, which is secure adaptively under the standard model. We construct this scheme by making use of an "encoding technique" which represents the MAS by their minimal sets to encrypt the messages. To date, for all traceable CP-ABE schemes, their encryption costs grow linearly with the MAS size, the decryption costs grow linearly with the qualified rows in the span programs. However, in our traceable CP-ABE, the ciphertext is linear with the minimal sets, and decryption needs merely three bilinear pairing computations and two exponent computations, which improves the efficiency extremely and has constant decryption. At last, the detailed security and traceability proof is given.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.5
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• pp.2718-2731
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• 2019

Conjunctive keyword search encryption is an important technique for protecting sensitive data that is outsourced to cloud servers. However, the process of searching outsourced data may facilitate the leakage of sensitive data. Thus, an efficient data search approach with high security is critical. To solve this problem, an efficient conjunctive keyword search scheme based on ciphertext-policy attribute-based encryption is proposed for cloud storage environment. This paper proposes an efficient mechanism for removing the secure channel and resisting off-line keyword-guessing attacks. The storage overhead and the computational complexity are regardless of the number of keywords. This scheme is proved adaptively secure based on the decisional bilinear Diffie-Hellman assumption in the standard model. Finally, the results of theoretical analysis and experimental simulation show that the proposed scheme has advantages in security, storage overhead and efficiency, and it is more suitable for practical applications.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.4
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• pp.1307-1329
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• 2022

This paper proposes an improved Pseudorandom Sequence Generator (PRSG) based on the concept of modular arithmetic systems with non-integral numbers. The generated random sequence use in various cryptographic applications due to its unpredictability. Here the mathematical model is designed to solve the problem of the non-uniform distribution of the sequences. In addition, PRSG has passed the standard statistical and empirical tests, which shows that the proposed generator has good statistical characteristics. Finally, image encryption has been performed based on the sort-index method and diffusion processing to obtain the encrypted image. After a thorough evaluation of encryption performance, there has been no direct association between the original and encrypted images. The results show that the proposed PRSG has good statistical characteristics and security performance in cryptographic applications.