• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.1
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• pp.302-322
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• 2021

In the system of ciphertext policy attribute-based encryption (CP-ABE), only when the attributes of data user meets the access structure established by the encrypter, the data user can perform decryption operation. So CP-ABE has been widely used in personal health record system (PHR). However, the problem of key abuse consists in the CP-ABE system. The semi-trusted authority or the authorized user to access the system may disclose the key because of personal interests, resulting in illegal users accessing the system. Consequently, aiming at two kinds of existing key abuse problems: (1) semi-trusted authority redistributes keys to unauthorized users, (2) authorized users disclose keys to unauthorized users, we put forward a CP-ABE scheme that has authority accountability, user traceability and supports arbitrary monotonous access structures. Specifically, we employ an auditor to make a fair ruling on the malicious behavior of users. Besides, to solve the problem of user leaving from the system, we use an indirect revocation method based on trust tree to implement user revocation. Compared with other existing schemes, we found that our solution achieved user revocation at an acceptable time cost. In addition, our scheme is proved to be fully secure in the standard model.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.4028-4049
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• 2014

Attribute-based encryption (ABE) is a promising cryptographic primitive for implementing fine-grained data sharing in cloud computing. However, before ABE can be widely deployed in practical cloud storage systems, a challenging issue with regard to attributes and user revocation has to be addressed. To our knowledge, most of the existing ABE schemes fail to support flexible and direct revocation owing to the burdensome update of attribute secret keys and all the ciphertexts. Aiming at tackling the challenge above, we formalize the notion of ciphertext-policy ABE supporting flexible and direct revocation (FDR-CP-ABE), and present a concrete construction. The proposed scheme supports direct attribute and user revocation. To achieve this goal, we introduce an auxiliary function to determine the ciphertexts involved in revocation events, and then only update these involved ciphertexts by adopting the technique of broadcast encryption. Furthermore, our construction is proven secure in the standard model. Theoretical analysis and experimental results indicate that FDR-CP-ABE outperforms the previous revocation-related methods.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.7
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• pp.1935-1950
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• 2023

The arrival of the Internet of Things and 5G technology enables users to rely on edge computing platforms to process massive data. Data sharing based on edge computing refines the efficiency of data collection and analysis, saves the communication cost of data transmission back and forth, but also causes the privacy leakage of a lot of user data. Based on attribute-based encryption and blockchain technology, we design a fine-grained access control scheme for data in edge computing, which has the characteristics of verifiability, support for outsourcing decryption and user attribute revocation. User attributes are authorized by multi-attribute authorization, and the calculation of outsourcing decryption in attribute encryption is completed by edge server, which reduces the computing cost of end users. Meanwhile, We implemented the user's attribute revocation process through the dual encryption process of attribute authority and blockchain. Compared with other schemes, our scheme can manage users' attributes more flexibly. Blockchain technology also ensures the verifiability in the process of outsourcing decryption, which reduces the space occupied by ciphertext compared with other schemes. Meanwhile, the user attribute revocation scheme realizes the dynamic management of user attribute and protects the privacy of user attribute.

• Journal of Korea Multimedia Society
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• v.18 no.4
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• pp.499-505
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• 2015

Security supports are a significant factor in the design of mobile ad hoc networks. In the dynamic topology where the node changes frequently, private key generation and revocation for newly joining and leaving nodes must be considered. In addition, the identities of individual nodes must be protected as well in mobile networks to avoid personal privacy concerns. This paper proposes ID-based private key revocation scheme and non-interactive key agreement scheme in anonymous MANETs. The proposed scheme provides the user privacy using pseudonyms and private key generation and revocation schemes with consideration of dynamic user changes. Therefore, our schemes can be applied in dynamic and privacy-preserving MANETs which are helpful to share multimedia data.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.2
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• pp.41-47
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• 2003

Revocation scheme is a re-keying scheme for dynamically changing group in multicast environment. In this paper, we propose two variants of the previously proposed revocation scheme, on the purpose of reducing the amount of computations group members should perform. Also proposed is a method of allowing unlimited number of member revocations.

• The KIPS Transactions:PartC
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• v.14C no.7
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• pp.553-558
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• 2007

In this paper, we introduce a set of structures and algorithms for communication efficient public key revocation in wireless sensor networks. Unlike the traditional networks, wireless sensor network is subjected to resources constraints. Thus, traditional public key revocation mechanisms such like the ordinary certificate revocation list is unsuitable to be used. This unsuitability is due to the huge size of required representation space for the different keys' identifiers and the revocation communication as the set of revoked keys grow. In this work, we introduce two communication-efficient schemes for the certificate revocation. In the first scheme, we utilize the complete subtree mechanism for the identifiers representation which is widely used in the broadcast encryption/user revocation. In the second scheme, we introduce a novel bit vector representation BVS which uses vector of relative identifiers occurrence representation. We introduce different revocation policies and present corresponding modifications of our scheme. Finally, we show how the encoding could reduce the communication overhead as well. Simulation results and comparisons are provided to show the value of our work.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.5
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• pp.1634-1652
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• 2022

Due to the increasing need for data sharing in the age of big data, how to achieve data access control and implement user permission revocation in the blockchain environment becomes an urgent problem. To solve the above problems, we propose a novel blockchain-based data sharing scheme (BDSS) with fine-grained access control and permission revocation in this paper, which regards the medical environment as the application scenario. In this scheme, we separate the public part and private part of the electronic medical record (EMR). Then, we use symmetric searchable encryption (SSE) technology to encrypt these two parts separately, and use attribute-based encryption (ABE) technology to encrypt symmetric keys which used in SSE technology separately. This guarantees better fine-grained access control and makes patients to share data at ease. In addition, we design a mechanism for EMR permission grant and revocation so that hospital can verify attribute set to determine whether to grant and revoke access permission through blockchain, so it is no longer necessary for ciphertext re-encryption and key update. Finally, security analysis, security proof and performance evaluation demonstrate that the proposed scheme is safe and effective in practical applications.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.958-964
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• 2005

WLAN user authentication is mostly based on user password resulting in vulnerability to the notorious 'offline dictionary attack'. As a way around this problem. EAP-TTLS and PEAP protocols are increasing finding their way into WLANs, which are a sort of combination of password protocols and the TLS public-key protocol. This leads to the use of the public-key certificate of the WLAM authentication server, and naturally the concern arises about its revocation status. It seems, however, that any proper soulution has not been provided to address this concern. We propose a very efficent and proper solution to check the certificate revocation status.

• The KIPS Transactions:PartC
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• v.19C no.1
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• pp.63-70
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• 2012

To ensure privacy of individual information in remote healthcare service, health data should be protected through a secure technology such as encryption scheme. Only user who delegated decryption right can access to sensitive health data and delegator needs capability for revocating access privilege. Recently, in ubiquitous environment, CP-ABTD(Ciphertext-Policy Attribute-Based Threshold Decryption with Flexible Delegation and Revocation of User Attributes) which extends CP-ABE(Ciphertext-Policy Attribute-Based Encryption) has been proposed for these requirements. In this paper, we construct remote healthcare monitoring system with delegation and revocation capability for attribute in CP-ABTD. Finally, we analyze collusion attack between users in our system.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.6
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• pp.1281-1293
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• 2017

In 2001, Boneh and Franklin proposed Identity-Based Encryption(IBE) that does not require a certificate like Public Key Infrastructure(PKI) by using user's Identity as a public key. However, IBE has a key escrow problem because the Private Key Generator(PKG), who is a trusted authority, generates a secret key of every user. Also, it does not support efficient revocation when the user's secret key is exposed or the system needs to revoke the user. Therefore, in order to use IBE as PKI that currently used, it is necessary to solve the key escrow problem and the revocation problem. In this paper, to solve those two problems, we suggest Accountable Authority Revocable IBE(A-RIBE) based on Accountable Authority IBE that mitigates the key escrow problem and Revocable IBE that solves the revocation problem. Also, we define the security model suitable foe A-RIBE, and analyze the principle of designing A-RIBE according to based A-IBE and RIBE and their advantage and disadvantage.