• KIPS Transactions on Computer and Communication Systems
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• v.11 no.8
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• pp.259-268
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• 2022

With prosperous usage of cloud services to improve management efficiency due to the explosive increase in data volume, various cryptographic techniques are being applied in order to preserve data privacy. In spite of the vast computing resources of cloud systems, decrease in storage efficiency caused by redundancy of data outsourced from multiple users acts as a factor that significantly reduces service efficiency. Among several approaches on privacy-preserving data deduplication over encrypted data, in this paper, the research results for improving efficiency of encrypted data deduplication using trusted execution environment (TEE) published in the recent USENIX ATC are analysed in terms of security and efficiency of the participating entities. We present a way to improve the stability of a key-managing server by integrating it with individual clients, resulting in secure deduplication without independent key servers. The experimental results show that the communication efficiency of the proposed approach can be improved by about 30% with the effect of a distributed key server while providing robust security guarantees as the same level of the previous research.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2007.02a
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• pp.116-119
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• 2007

In a keyword search scheme a user stores encrypted data on an untrusted server and gives a database manager a capability for a keyword which enables a database manager to find encrypted data containing the keyword without revealing the keyword to the database manager. Conjunctive keyword search scheme enables a user to obtain data containing all of several keywords through only one query. One of the security requirements of conjunctive keyword search schemes is that a malicious adversary should not be able to generate new valid capabilities from the observed capabilities. In U:5 paper we show that conjunctive keyword search schemes are not secure. In particular, given two capabilities corresponding two sets of keywords, an adversary is able to generate a new capability corresponding to the dierence set of two keywords sets.

• Journal of the Optical Society of Korea
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• v.18 no.4
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• pp.401-405
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• 2014

In this paper, we propose an accumulation encoding scheme based on double random phase encryption (DRPE) for multiple-image transmission. The proposed scheme can be used for a low-complexity DRPE system due to the simple structure of the accumulation encoder and decoder. For accumulation encoding of multiple images, all of the previously encrypted data are added, and hence the accumulation encoding can improve the security of the DRPE-encrypted data. We present a scheme for encryption and decryption for DRPE-based accumulation encoding, and a method for accumulation encoding and decoding. Finally, simulation results verify that the DRPE-based accumulation encoding scheme for multiple images is powerful in terms of data security.

• 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.

• Journal of Information Processing Systems
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• v.10 no.2
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• pp.215-222
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• 2014

In this paper, we discuss optical encryption and decryption considering wireless communication channels. In wireless communication systems, the wireless channel causes noise and fading effects of the transmitted information. Optical encryption technique such as double-random-phase encryption (DRPE) is used for encrypting transmitted data. When the encrypted data is transmitted, the information may be lost or distorted because there are a lot of factors such as channel noise, propagation fading, etc. Thus, using digital modulation and maximum likelihood (ML) detection, the noise and fading effects are mitigated, and the encrypted data is estimated well at the receiver. To the best of our knowledge, this is the first report that considers the wireless channel characteristics of the optical encryption technique.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.11
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• pp.5560-5579
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• 2019

Searchable symmetric encryption (SSE) scheme can perform search on encrypted data directly without revealing the plain data and keywords. At present, many constructive SSE schemes were proposed. However, they cannot really resist the malicious adversary, because it (i.e., the cloud server) may delete some important data. As a result, it is very likely that the returned search results are incorrect. In order to better guarantee the integrity of outsourcing data, and ensure the correction of returned search results at the same time, in this paper, we combine SSE with blockchain (BC), and propose a SSE-on-BC framework model. We then construct two concrete schemes based on the size of the data, which can better provide privacy protection and integrity verification for data. Lastly, we present their security and performance analyses, which show that they are secure and feasible.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.11
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• pp.4522-4536
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• 2020

Nowadays, cloud is the fastest emerging technology in the IT industry. We can store and retrieve data from the cloud. The most frequently occurring problems in the cloud are security and privacy preservation of data. For improving its security, secret information must be protected from various illegal accesses. Numerous traditional cryptography algorithms have been used to increase the privacy in preserving cloud data. Still, there are some problems in privacy protection because of its reduced security. Thus, this article proposes an ElGamal Elliptic Curve (EGEC) Homomorphic encryption scheme for safeguarding the confidentiality of data stored in a cloud. The Users who hold a data can encipher the input data using the proposed EGEC encryption scheme. The homomorphic operations are computed on encrypted data. Whenever user sends data access permission requests to the cloud data storage. The Cloud Service Provider (CSP) validates the user access policy and provides the encrypted data to the user. ElGamal Elliptic Curve (EGEC) decryption was used to generate an original input data. The proposed EGEC homomorphic encryption scheme can be tested using different performance metrics such as execution time, encryption time, decryption time, memory usage, encryption throughput, and decryption throughput. However, efficacy of the ElGamal Elliptic Curve (EGEC) Homomorphic Encryption approach is explained by the comparison study of conventional approaches.

• International journal of advanced smart convergence
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• v.11 no.4
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• pp.163-169
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• 2022

In this paper, we propose a data hiding technique that effectively hides confidential data in the LSB of an image pixel by using the characteristics of the neighboring pixels of the image and the encryption techniques. In the proposed technique, the boundary surface of the image and the flat surface with little change in pixel values are investigated. At the boundary surface of the image, 1 bit of confidential data is encrypted and hidden in the LSB of the boundary pixel to preserve the characteristics of the boundary surface. In the pixels of the plane where the change in pixel value is small, 2 bits secret data is encrypted and hidden in the lower 2 bits of the corresponding pixel. In this way, when confidential data is hidden in an image, the amount of confidential data hidden in the image is greatly increased while maintaining excellent image quality. In addition, the security of hidden confidential data is strongly maintained. When confidential data is hidden by applying the proposed technique, the amount of confidential data concealed increases by up to 92.2% compared to the existing LSB method. The proposed technique can be effectively used to hide copyright information in commercial images.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.4
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• pp.739-751
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• 2014

We are using our smartphone for our business as well as ours lives. Thus, user's privacy data and a company secret are stored at smartphone. By the way, the saved data on smartphone database can be exposed to a malicous attacker when a malicous app is installed in the smartphone or a user lose his/her smartphone because all data are stored as form of plaintext in the database. To prevent this disclosure of personal information, we need a database encryption method. However, if a database is encrypted, it causes of declining the performance. For example, when we search specific data in condition with encrypted database, we should decrypt all data stored in the database or search sequentially the data we want with accompanying overhead[1]. In this paper, we propose an efficient and searchable encryption method using variable length bloom filter under limited resource circumstances(e.g., a smartphone). We compare with existing searchable symmetric encryption. Also, we implemented the proposed method in android smartphone and evaluated the performance the proposed method. As a result through the implementation, We can confirm that our method has over a 50% improvement in the search speed compared to the simple search method about encrypted database and has over a 70% space saving compared to the method of fixed length bloom filter with the same false positive rate.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.3
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• pp.505-514
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• 2012

Because people usually establish their online social network based on their offline relationship, the social networks (i.e., the graph of friendship relationships) are often used to share contents. Mobile devices let it easier in these days, but it also increases the privacy risk such as access control of shared data and relationship exposure to untrusted server. To control the access on encrypted data and protect relationship from the server, M. Atallah et al. proposed a hop-based scheme in 2009. Their scheme assumed a distributed environment such as p2p, and each user in it shares encrypted data on their social network. On the other hand, it is very inefficient to keep their relationship private, so we propose an improved scheme. In this paper, among encrypted contents and relationships, some authenticated users can only access the data in distributed way. For this, we adopt 'circular-secure symmetric encryption' first. Proposed scheme guarantees the improved security and efficiency compared to the previous work.