Browsing by Author "Tzeng, Wen-Guey"

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A Cooperative Game-Theoretic Model in Cloud Storage Auditing
(2020-01-01)
Lin, Chung-Yi
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
In the traditional cloud storage auditing, users individually audit the cloud storage provider (CSP). However, users may pay the redundant auditing cost when they have similar auditing results. For example, a lot of users may get fail results when the CSP's service occurs accidents. In the worst case, the overall auditing cost linearly increases with the number of users. We propose a cooperative auditing model to let user share their auditing results in a friendship-based social network so that their overall auditing cost can be reduced. Furthermore, we design an auditing coalition game based on cooperative game theory, where not only users' individual interest but their entire benefit is c onsidered. We present two algorithms to find out an optimal way of forming auditing coalitions. The first algorithm determines an optimal coalition in one iteration. In the second algorithm, after iteratively adjusting users' trust relationships, users may change to join another coalition if they receive wrong auditing results. The results of the one-iteration experiment show that the more number of users, the more auditing cost reduction. Specifically, the auditing cost can be reduced by 96% with respect to the original non-cooperative auditing model. In the multi-iteration experiment, the accuracy of users' auditing results can be improved from 88% to 100%.
A Decentralized Repair Mechanism for Decentralized Erasure Code based Storage Systems
(2011-01-01)
Lin, Hsiao-Ying
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Tzeng, Wen-Guey
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Lin, Bao-Shuh
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資訊工程學系
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Department of Computer Science
Erasure code based distributed storage systems provide data robustness by storing encoded-fragments over servers. To maintain data robustness, a repair mechanism recovers a storage system from server failures by repairing encoded-fragments. For decentralized erasure code based storage systems, we propose a decentralized repair mechanism. Our mechanism has the following features. Firstly, an encoded-fragment is replenished by a combination of a number u of encoded-fragments that are randomly chosen. Secondly, the number u depends on the number of the available encoded-fragments and is independent of the pattern of missing encoded-fragments. Thirdly, multiple encoded-fragments are simultaneously replenished in parallel. We measure the communication cost in terms of the number u of required network connections for replenishing an encoded-fragment. We then conducted a numerical analysis by using traces of real systems. We find that our requirement on u is smaller than that from existing methods. Both theoretical and numerical results show that our decentralized repair mechanism outperforms existing ones in terms of the communication cost under the same consideration of efficiency cost for storage.
A light-weight bit commitment protocol based on unpredictable channel noise
(2019-01-10)
Guan, Albert
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
Bit commitment is an important tool in the design of many secure cryptographic protocols, such as coin flipping, zero-knowledge proof, and secure computation. In this paper, we present a computationally light-weight bit commitment protocol over a noisy channel. For the security of the proposed protocol, we show that the receiver has almost no information about the committer's secret due to unpredictability of the noises in the communication channel. Hence, the security of our bit commitment protocol does not depend on hard problems; it is information-theoretically secure. Furthermore, the protocol needs only exclusive-or operations. Thus, it is computationally light-weight, and it can be used in the devices whose computing resources are limited. (C) 2018 Elsevier B.V. All rights reserved.
A Public-Key Traitor Tracing Scheme with an Optimal Transmission Rate
(2009)
Chen, Yi-Ruei
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
The way of transmitting the encrypted digital content, to the legitimate subscribers over a broadcast channel has wide commercial applications; such as Pay-TV, DVD, etc In order to discourage the legitimate subscribers from giving away their decryption keys, the traitor tracing scheme collies up In this paper, we propose a public-key traitor tracing scheme that has optimal transmission rate In other words, our scheme enables everyone to transmit the encrypted digital contents almost, without, any redundancy As for tracing, our scheme supports black-box tracing, i.e., identifying colluders without opening the pirate decode Moreover, in our scheme, the storage requirement, for legitimate subscribers and digital content broadcasters is smaller than that of previous schemes
A Robust Algorithm for Predicting Attacks Using Collaborative Security Logs
(2020-05-01)
Rezapour, Amir
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
As networks become ubiquitous in our daily lives, users rely more on networks for exchanging data and communication. However, numerous new and sophisticated attacks that endanger security of users have been reported. In practice, blacklisting illicit sources has been a fundamental defense strategy in recent years. In this paper, we propose a predictor that is based on the observations from a centralized log-sharing infrastructure. Our observations include the direct relation between attackers and victims, victim similarities, and attacker correlations. We compile a customized blacklist for each Dshield.org contributor using a weighted function of direct and indirect relations between victims and attackers. This list not only offers a significantly higher prediction ratio, but also includes source addresses with potentially higher threats. We evaluate our predictor using two months of malicious activities acquired from Dshield.org. The experimental results demonstrate a significant improvement over previous algorithms.
A Secure Decentralized Erasure Code for Distributed Networked Storage
(2010-11-01)
Lin, Hsiao-Ying
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
Distributed networked storage systems provide the storage service on the Internet. We address the privacy issue of the distributed networked storage system. It is desired that data stored in the system remain private even if all storage servers in the system are compromised. The major challenge of designing these distributed networked storage systems is to provide a better privacy guarantee while maintaining the distributed structure. To achieve this goal, we introduce secure decentralized erasure code, which combines a threshold public key encryption scheme and a variant of the decentralized erasure code. Our secure distributed networked storage system constructed by the secure decentralized erasure code is decentralized, robust, private, and with low storage cost.
A Secure Decentralized Erasure Code for Distributed Networked Storage
(2010-11-01)
Lin, Hsiao-Ying
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
Distributed networked storage systems provide the storage service on the Internet. We address the privacy issue of the distributed networked storage system. It is desired that data stored in the system remain private even if all storage servers in the system are compromised. The major challenge of designing these distributed networked storage systems is to provide a better privacy guarantee while maintaining the distributed structure. To achieve this goal, we introduce secure decentralized erasure code, which combines a threshold public key encryption scheme and a variant of the decentralized erasure code. Our secure distributed networked storage system constructed by the secure decentralized erasure code is decentralized, robust, private, and with low storage cost.
A Secure Erasure Code-Based Cloud Storage System with Secure Data Forwarding
(2012-06-01)
Lin, Hsiao-Ying
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
A cloud storage system, consisting of a collection of storage servers, provides long-term storage services over the Internet. Storing data in a third party's cloud system causes serious concern over data confidentiality. General encryption schemes protect data confidentiality, but also limit the functionality of the storage system because a few operations are supported over encrypted data. Constructing a secure storage system that supports multiple functions is challenging when the storage system is distributed and has no central authority. We propose a threshold proxy re-encryption scheme and integrate it with a decentralized erasure code such that a secure distributed storage system is formulated. The distributed storage system not only supports secure and robust data storage and retrieval, but also lets a user forward his data in the storage servers to another user without retrieving the data back. The main technical contribution is that the proxy re-encryption scheme supports encoding operations over encrypted messages as well as forwarding operations over encoded and encrypted messages. Our method fully integrates encrypting, encoding, and forwarding. We analyze and suggest suitable parameters for the number of copies of a message dispatched to storage servers and the number of storage servers queried by a key server. These parameters allow more flexible adjustment between the number of storage servers and robustness.
An Effective Integrity Check Scheme for Secure Erasure Code-Based Storage Systems
(2015-09-01)
Shen, Shiuan-Tzuo
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Lin, Hsiao-Ying
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
In the application of cloud storage, a user no longer possesses his files in his local depository. Thus, he is concerned about the security of the stored files. Data confidentiality and data robustness are the main security issues. For data confidentiality, the user can first encrypt files and then store the encrypted files in a cloud storage. For data robustness, there are two concerns: service failure, and service corruption. We are concerned about data robustness in cloud storage services. Lin and Tzeng proposed a secure erasure code-based storage system with multiple key servers recently. Their system supports a repair mechanism, where a new storage server can compute a new ciphertext from the ciphertexts obtained from the remaining storage servers. Their system considers data confidentiality in the cloud, and data robustness against storage server failure. In this paper, we propose an integrity check scheme for their system to enhance data robustness against storage server corruption, which returns tampered ciphertexts. With our integrity check scheme, their storage system can deal with not only the problem of storage server failure, but also the problem of storage server corruption. The challenging part of our work is to have homomorphic integrity tags. New integrity tags can be computed from old integrity tags by storage servers without involvement of the user\'s secret key or backup servers. We prove the security of our integrity check scheme formally, and establish the parameters for achieving an overwhelming probability of a successful data retrieval.
An Online Subject-Based Spam Filter Using Natural Language Features
(2017-01-01)
Lee, Chih-Ning
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Chen, Yi-Ruei
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
This paper proposes an online subject-based spam filter built upon an extended version of weighted naive Bayesian (WNB) classifier. The spam filter checks email subjects only. It is faster than spam filters that scan whole body of emails and useful even spam senders temper email bodies to avoid filtering. In addition to the widely used bag-of-word feature, we further consider statistical and nature language features to discover new characteristics from email subjects. In online learning, we use an extended WNB classifier. It is not only computationally efficient, but also more adaptive to the changes of spams with new malicious campaigns. The proposed classifier is immune to the spams with malicious campaigns beyond contemplation. We evaluate the performance of our spam filter on 8 well-known ham-spam email datasets from TREC and Enron-Spam corpus. Our approach achieves 94.85% of accuracy and 95.8% of F1-measure on TREC datasets, and 95.74% of accuracy and 97.2% of F1-measure on Enron-Spam datasets. Compared with previous works of the same line, our approach has 2.43%, 2.3%, and 3.2% improvements on accuracy, true positive rate, and false positive rate, respectively.
An Optimal Data Hiding Scheme With Tree-Based Parity Check
(2011-03-01)
Hou, Chung-Li
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Lu, ChangChun
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Tsai, Shi-Chun
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Tzeng, Wen-Guey
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資訊工程學系
Reducing distortion between the cover object and the stego object is an important issue for steganography. The tree-based parity check method is very efficient for hiding a message on image data due to its simplicity. Based on this approach, we propose a majority vote strategy that results in least distortion for finding a stego object. The lower embedding efficiency of our method is better than that of previous works when the hidden message length is relatively large.
Anonymous Password Based Authenticated Key Exchange with Sub-Linear Communication
(2009-05-01)
Lin, Hsiao-Ying
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
In this paper we propose a new anonymous password-based authenticated key exchange protocol. The communication cost of our protocol is sub-linear O(root N), which improves a previous one of O(N) cost, where N is the number Of users in the system. We show that the session key is secure against an active adversary in the random oracle model and identity anonymity is secure against a semi-honest adversary in the standard model.
Cheating prevention in visual cryptography
(2007-01-01)
Hu, Chih-Ming
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
Visual cryptography (VC) is a method of encrypting a secret image into shares such that stacking a sufficient number of shares reveals the secret image. Shares are usually presented in transparencies. Each participant holds a transparency. Most of the previous research work on VC focuses on improving two parameters: pixel expansion and contrast. In this paper, we studied the cheating problem in VC and extended VC. We considered the attacks of malicious adversaries who may deviate from the scheme in any way. We presented three cheating methods and applied them on attacking existent VC or extended VC schemes. We improved one cheat-preventing scheme. We proposed a generic method that converts a VCS to another VCS that has the property of cheating prevention. The overhead of the conversion is near optimal in both contrast degression and pixel expansion.
Conditional oblivious cast
(2006)
Chu, Cheng-Kang
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
We introduce a new notion of conditional oblivious cast (COC), which involves three parties: a sender S and two receivers A and B. Receivers A and B own their secrets x and y, respectively, and the sender S holds the message m. In a COC scheme for the predicate Q (Q-COC), A and B send x and y in a masked form to S, and then S sends m to A and B such that they get m if and only if Q(x, y) = 1. Besides, the secrets x and y can not be revealed to another receiver nor the sender. We also extend COC to 1-out-of-2 COC (COC(2)/(1)) in which S holds two messages m(0) and m(1), and A and B get m(1) if Q(x, y) = 1 and m(0) otherwise. We give the definitions for COC and COC(2)/(1), and propose several COC and COC(2)/(1) schemes for "equality", "inequality", and "greater than" predicates. These are fundamental schemes that are useful in constructing more complex secure interactive protocols. Our schemes are efficiently constructed via homomorphic encryption schemes and proved secure under the security of these encryption schemes.
Delegable Provable Data Possession for Remote Data in the Clouds
(2011)
Shen, Shiuan-Tzuo
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
Many storage systems need to do authorized verification for data integrity. For example, a user stores his data into cloud storage servers and shares his data with his friends. They check data integrity periodically to ensure data intact. However, they don't want a stranger to check data integrity on their data. Therefore, public verification is undesired in this situation. The user can share his private key to his friends for private verification. However, his friends may reveal his private key to others. In this paper, we proposed the delegable provable data possession (delegable PDP) model to solve this problem. Delegable PDP allows a user to control who can check data integrity of his data, and guarantee that delegated verifiers cannot re-delegate this verification capability to others. Delegable PDP enjoys advantage of authorized verification and convenience of public verification. We define a delegable PDP model and provide a construction for it. User U generates verifiable tags of his data and the delegation key dk(upsilon ->nu) for delegated verifier nu, upsilon uploads his data, tags, and dk(upsilon ->nu) to storage servers. When integrity check, storage servers can use dku v to transform U's tags into the form that V can verify with his private key sky. Our model allows U to revoke V's verification capability by removing dku v from storage servers directly. We prove our protocol secure in the random oracle model. Our protocol achieves proof unforgeability, proof indistinguishability, and delegation key unforgeability.
Effective Botnet Detection Through Neural Networks on Convolutional Features
(2018-01-01)
Chen, Shao-Chien
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Chen, Yi-Ruei
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
Botnet is one of the major threats on the Internet for committing cybercrimes, such as DDoS attacks, stealing sensitive information, spreading spams, etc. It is a challenging issue to detect modern botnets that are continuously improving for evading detection. In this paper, we propose a machine learning based botnet detection system that is shown to be effective in identifying P2P botnets. Our approach extracts convolutional version of effective flow-based features, and trains a classification model by using a feed-forward artificial neural network. The experimental results show that the accuracy of detection using the convolutional features is better than the ones using the traditional features. It can achieve 94.7% of detection accuracy and 2.2% of false positive rate on the known P2P botnet datasets. Furthermore, our system provides an additional confidence testing for enhancing performance of botnet detection. It further classifies the network traffic of insufficient confidence in the neural network. The experiment shows that this stage can increase the detection accuracy up to 98.6% and decrease the false positive rate up to 0.5%.
Efficient Encoding and Decoding with Permutation Arrays
(2008)
Lin, Te-Tsung
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Tsai, Shi-Chun
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
An (n, d) permutation array (PA) is a subset of S(n) with the property that the distance (under any distance metric, such as Hamming) between any two permutations in the array is at least d, which becomes popular recently for communication over power line. We use l(infinity)-norm to measure the distance between permutations, and give a construction of permutation arrays under l(infinity)-norm together with efficient encoding and decoding algorithms. This construction is the first of its kind.
Efficient Identity-Committable Signature and Group-Oriented Ring Signature Schemes
(2009-09-01)
Chu, Cheng-Kang
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
The identity of "Deep Throat", a pseudonym of the information source in the Watergate scandal, remained mysterious for more than three decades. In 2005, an ex-FBI official claimed that he was the anonymous source. Nevertheless, some are still inconvinced. In this paper, we introduce a new notion of identity-committable signatures (ICS) to ensure the anonymity of "Deep Throat" inside a group. A member of an organization can sign a message on behalf of himself (regular signature) or the organization (identity-committed signature). In the latter case, the signer's identity is hidden from anyone, and can be opened by himself only. We describe the requirements of ICS and give the formal definition of it. Then we extend the notion of ICS to group-oriented ring signatures (GRS) which further allow the signer to hide his identity behind multiple groups. Since the signer can include the whole members of a group at a time, our GRS scheme is more efficient and practical than general ring signature schemes. Finally, we provide concrete constructions of ICS and GRS with information-theoretic anonymity, that is, the identity of the signer is fully-protected.
Efficient k-out-of-n oblivious transfer schemes
(2008)
Chu, Cheng-Kang
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Tzeng, Wen-Guey
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交大名義發表
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National Chiao Tung University
Oblivious transfer is an important cryptographic protocol in various security applications. For example, in on-line transactions, a k-out-of-n oblivious transfer scheme allows a buyer to privately choose k-out of n digital goods from a merchant without learning information about other n-k goods. In this paper, we propose several efficient two-round k-out-of-n oblivious transfer schemes, in which the receiver R sends O(k) messages to the sender S, and S sends O( n) messages back to R. The schemes provide unconditional security for either sender or receiver. The computational security for the other side is based on the Decisional Diffie-Hellman (DDH) or Chosen-Target Computational Diffie-Hellman (CT-CDH) problems. Our schemes have the nice property of universal parameters, that is, each pair of R and S need not hold any secret before performing the protocol. The system parameters can be used by all senders and receivers without any trapdoor specification. In some cases, our OT(n)(k) schemes are the most efficient ones in terms of the communication cost, either in rounds or the number of messages. Moreover, one of our schemes is extended to an adaptive oblivious transfer scheme. In that scheme, S sends O( n) messages to R in one round in the commitment phase. For each query of R, only O( 1) messages are exchanged and O( 1) operations are performed. The preliminary version of this paper was published at PKC ' 05 [ Chu and Tzeng 2005].
Efficient large-scale distributed key generation against burst interruption
(2007)
Ou, Jheng-Ru
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Tsai, Shi-Chun
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Tzeng, Wen-Guey
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資訊工程學系
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Department of Computer Science
A distributed key generation scheme allows the key servers to distributively share a secret key and then compute the corresponding public key. Canny and Sorkin (Canny and Sorkin, 2004) proposed a probabilistic threshold distributed key generation scheme that is suitable for the case that the number of key servers is large. The communication cost of their scheme is much less than that of previous schemes. Nevertheless, it is possible to improve their scheme in some aspects. In this paper we employ the randomness technique to cope with some problems encountered by their scheme. Our contribution is twofold. Firstly, our scheme is secure against a large cluster of dishonest key servers. Secondly, our scheme has better performance in some aspects. We support this point by a series of simulation experiments. As a result, our scheme and Canny and Sorkin's scheme can be used in different situations.