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Toru Nakanishi - One of the best experts on this subject based on the ideXlab platform.
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efficient blacklistable Anonymous Credential system with reputation using a pairing based accumulator
Iet Information Security, 2020Co-Authors: Toru Nakanishi, Takeshi KanataniAbstract:As privacy-enhancing authentications without any TTP (Trusted Third Party), blacklistable Anonymous Credential systems with reputation have been proposed. However, the previous systems have the efficiency problem: The authentication data size is O ( L ) or O ( K ) , where L is the reputation list, and K is the size of a window indicating the most recent K authentications of the user. Therefore, the previous systems suffer from O ( L ) or O ( K ) -size data in each authentication. In addition, the authentication needs the computation of O ( L ) or O ( K ) exponentiations. In this paper, an efficient blacklistable Anonymous Credential system with reputation is proposed. In our system, the data size of the authentication is O ( 1 ) . Furthermore, although the computational costs in the authentication depend on some parameters, the parameter-related costs are only multiplications instead of exponentiations. Compared to the previously proposed blacklistable system FARB with the constant computational and communication costs, our system has the advantage that the clear/redeem protocol only has to be executed every interval instead of every session. For constructing our system, we newly introduce the concept of an accumulator for reputation, and propose an efficient construction.
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an Anonymous Credential system with constant size attribute proofs for cnf formulas with negations
International Workshop on Security, 2019Co-Authors: Ryo Okishima, Toru NakanishiAbstract:To enhance the user’s privacy in electronic ID, Anonymous Credential systems have been researched. In the Anonymous Credential system, a trusted issuing organization first issues a certificate certifying the user’s attributes to a user. Then, in addition to the possession of the certificate, the user can Anonymously prove only the necessary attributes. Previously, an Anonymous Credential system was proposed, where CNF (Conjunctive Normal Form) formulas on attributes can be proved. The advantage is that the attribute proof in the authentication has the constant size for the number of attributes that the user owns and the size of the proved formula. Thus, various expressive logical relations on attributes can be efficiently verified. However, the previous system has a limitation: the proved CNF formulas cannot include any negation. Therefore, in this paper, we propose an Anonymous Credential system with constant-size attribute proofs such that the user can prove CNF formulas with negations. For the proposed system, we extend the previous accumulator for the limited CNF formulas to verify CNF formulas with negations.
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An efficient blacklistable Anonymous Credentials without TTP of tracing authority using pairing-based accumulator
'Institute of Electronics Information and Communications Engineers (IEICE)', 2019Co-Authors: Yuu Aikou, Sadiah Shahidatul, Toru NakanishiAbstract:In conventional ID-based user authentications, privacy issues may occur, since users’ behavior histories are collected in Service Providers (SPs). Although Anonymous authentications such as group signatures have been proposed, these schemes rely on a Trusted Third Party (TTP) capable of tracing misbehaving users. Thus, the privacy is not high, because the TTP of tracing authority can always trace users. Therefore, the Anonymous Credential system using a blacklist without the TTP of tracing authority has been proposed, where blacklisted Anonymous users can be blocked. Recently, an RSA-based blacklistable Anonymous Credential system with efficiency improvement has been proposed. However, this system still has an efficiency problem: The data size in the authentication is O(K0), where K0 is the maximum number of sessions in which the user can conduct. Furthermore, the O(K0)-size data causes the user the computational cost of O(K0) exponentiations. In this paper, a blacklistable Anonymous Credential system using a pairing-based accumulator is proposed. In the proposed system, the data size in the authentication is constant for parameters. Although the user’s computational cost depends on parameters, the dependent cost is O(δBL · K) multiplications, instead of exponentiations, where δBL is the number of sessions added to the blacklist after the last authentication of the user, and K is the number of past sessions of the user. The demerit of the proposed system is O(n)-size public key, where n corresponds to the total number of all sessions of all users in the system. But, the user only has to download the public key once
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an efficient blacklistable Anonymous Credential system with reputation using pairing based accumulator
Trust Security And Privacy In Computing And Communications, 2018Co-Authors: Toru Nakanishi, Takeshi KanataniAbstract:To achieve the privacy-enhancing authentications without any TTP (Trusted Third Party), blacklistable Anonymous Credential systems have been proposed. In conventional blacklistable Anonymous Credential systems, a user is blacklisted after the user misbehaves once. Since it is too harsh to be of practical use, extended blacklistable Anonymous Credential systems based on reputation have been proposed. In the reputation-based system, each behavior of a user is given a score. The service provider publishes a reputation list of correspondences between session ID and the score. In the authentication, a user can Anonymously prove the total of his own scores. However, the previously proposed systems have the efficiency problem: The authentication data size is O(|L|) or O(K), where |L| is the size of the reputation list L, and K is the size of the following window. In the window type of systems, the authentication is based on a window with most recent K authentications of the user. When a past authentication becomes outside the window, the misbehaving of the authentication is forgiven. Thus, K should be as large as possible. Therefore, the previous systems suffer from O(|L|) or O(K)-size data in each authentication. In addition, in the previous systems, the authentication needs the computation of O(|L|) or O(K) exponentiations, which is heavy. In this paper, an efficient blacklistable Anonymous Credential system with reputation is proposed. In our system, the data size of the authentication does not depend on parameters such as |L| and K, and is O(1). Furthermore, although the computational costs in the authentication depend on some parameters, the parameter-related costs are only multiplications instead of exponentiations. For constructing our system, we newly introduce the concept of an accumulator for reputation, and show an efficient pairing-based construction. Using the accumulator, we construct the efficient blacklistable Anonymous Credential system with reputation.
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reduction of certificates in an Anonymous Credential system with proofs for monotone formulas on attributes
International Conference on Consumer Electronics, 2016Co-Authors: Shahidatul Sadiah, Toru NakanishiAbstract:Anonymous Credential systems enable a user to assure a service provider Anonymously the ownership of his certified attributes. We have previously proposed an Anonymous Credential system to prove that user's attributes satisfy a monotone formula, i.e., a logic relation with any AND/OR combinations without negations. However, this system has a limitation where the user can prove the formula only using a certificate of minimum attribute set, which is a subset of user's attribute set that contains one satisfying attribute for each OR relation. Thus, he is issued with 2|U| signatures of all subsets of U, where U is the set of user's attributes. In this paper, we propose an improvement to reduce the number of signatures to approximately √2|U| by dividing set U into two sets. We implemented the system using a fast pairing library, and measured the processing times and data sizes to show the effectiveness.
Nobuo Funabiki - One of the best experts on this subject based on the ideXlab platform.
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Anonymous Credential system with efficient proofs for monotone formulas on attributes
International Workshop on Security, 2015Co-Authors: Shahidatul Sadiah, Toru Nakanishi, Nobuo FunabikiAbstract:An Anonymous Credential system allows a user to convince a service provider Anonymously that he/she owns certified attributes. Previously, a system to prove AND and OR relations simultaneously by CNF formulas was proposed. To achieve a constant-size proof of the formula, this system adopts an accumulator that compresses multiple attributes into a single value. However, this system has a problem: the proof generation requires a large computational time in case of lots of OR literals in the formula. One of the example formulas consists of lots of birthdate attributes to prove age. This greatly increases the public parameters correspondent to attributes, which causes a large delay in the accumulator computation due to multiplications of lots of parameters. In this paper, we propose an Anonymous Credential system with constant-size proofs for monotone formulas on attributes, in order to obtain more efficiency in the proof generation. The monotone formula is a logic formula that contains any combination of AND and OR relations. Our approach to prove the monotone formula is that the accumulator is extended to be adapted to the tree expressing the monotone formula. Since the use of monotone formulas increases the expression capability of the attribute proof, the number of public parameters multiplied in the accumulator is greatly decreased, which impacts the reduction of the proof generationi¾?time.
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implementation of Anonymous Credential system with efficient proofs for monotone formulas on attributes excluding restriction
International Symposium on Computing and Networking, 2014Co-Authors: Shahidatul Sadiah, Toru Nakanishi, Nobuo FunabikiAbstract:An Anonymous Credential system allows a user to convince a service provider Anonymously that he/she owns certified attributes. Previously, we proposed an Anonymous Credential system to prove user's attributes to satisfy a monotone formula, i.e., A logic relation with any combination of AND/OR relations. However, this system has a restriction that the user can prove the monotone formula when only one attribute is true for any OR relation. Recently, we proposed the improved system to overcome the restriction, by adopting Linear Homonorphic (LH) signature scheme to generate a certificate that contains the minimum attribute set as required in the verification. However, the improved system has never been implemented, and thus the practicality is not evaluated. In this paper, we implement the system using a fast pairing library, and measure the processing times and data sizes, when changing the number of user's attributes and the size of the proved relation.
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An Implementation of a Pairing-Based Anonymous Credential System with Constant Complexity
2014Co-Authors: Amang Sudarsono, Toru Nakanishi, Nobuo FunabikiAbstract:Abstract—An Anonymous Credential system allows the user to convince a verifier of the possession of a certificate issued by the issuing authority Anonymously. One of the applications is the privacy-enhancing electronic ID (eID). A previously proposed Anonymous Credential system achieves the constant complexity for the number of user’s attributes. However, due to the use of RSA-based cryptography, it still suffers from a high cost computation. Recently, we proposed an Anonymous Credential system with the constant complexity using a pairingbased accumulator, where more efficient ECC (Elliptic Curve Cryptography) can be used instead of the RSA. In this paper, we present an implementation of the Anonymous Credential system in the application to the eID. We show the practicality of the system from experimental results that the processing times are constantly less than a second. Index Terms—Authentications, privacy, Anonymous Credentials, electronic ID, pairings A. Backgrounds I
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efficient proofs for cnf formulas on attributes in pairing based Anonymous Credential system
IEICE Transactions on Fundamentals of Electronics Communications and Computer Sciences, 2013Co-Authors: Nasima Begum, Toru Nakanishi, Nobuo FunabikiAbstract:To enhance user privacy, Anonymous Credential systems allow the user to convince a verifier of the possession of a certificate issued by the issuing authority Anonymously. In the systems, the user can prove relations on his/her attributes embedded into the certificate. Previously, a pairing-based Anonymous Credential system with constant-size proofs in the number of attributes of the user was proposed. This system supports the proofs of the inner product relations on attributes, and thus can handle the complex logical relations on attributes as the CNF and DNF formulas. However this system suffers from the computational cost: The proof generation needs exponentiations depending on the number of the literals in OR relations. In this paper, we propose a pairing-based Anonymous Credential system with the constant-size proofs for CNF formulas and the more efficient proof generation. In the proposed system, the proof generation needs only multiplications depending on the number of literals, and thus it is more efficient than the previously proposed system. The key of our construction is to use an extended accumulator, by which we can verify that multiple attributes are included in multiple sets, all at once. This leads to the verification of CNF formulas on attributes. Since the accumulator is mainly calculated by multiplications, we achieve the better computational costs.
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reducing public key size in an Anonymous Credential system for cnf formulas with constant size proofs
IEEE Global Conference on Consumer Electronics, 2013Co-Authors: Nasima Begum, Toru Nakanishi, Nobuo FunabikiAbstract:To enhance the user privacy at authentications, an Anonymous Credential system has been designed to allow a user to Anonymously convince a verifier of the possession of a certificate issued by the issuing authority. In this system, a user can prove relations on his/her attributes embedded into the certificate. Previously, we have proposed an Anonymous Credential system with constant-size proofs and faster proof generations for CNF formulas than the existing system. In the system, in the verification, some value should be included in some set Φ. Unfortunately, this system has a problem of requiring long public parameters that is proportional to the size of the set Φ. In this paper, we propose an extension to reduce the public key by separating this set Φ into two sets Φ1 and Φ2 with logarithmic sizes such that u1 ϵ Φ1 and u2 ϵΦ2 if and only if u1 + u2 ϵ Φ. Furthermore, we evaluate the efficiency based on the implementation.
Xiangguo Cheng - One of the best experts on this subject based on the ideXlab platform.
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a privacy preserving smart metering scheme using linkable Anonymous Credential
IEEE Transactions on Smart Grid, 2015Co-Authors: Feng Diao, Fangguo Zhang, Xiangguo ChengAbstract:Smart grid, as the next power grid, can efficiently monitor, predicate, and control energy generation/consumption by using the real-time users' electricity information. However, the fine-grained user energy consumption information may reveal the private information of the user. In this paper, we construct a linkable Anonymous Credential protocol based on Camenisch-Lysyanskaya (CL) signature. Then, we propose a privacy preserving smart metering scheme based on the new linkable Anonymous Credential. In addition to providing privacy protection for the user, our protocol also has the security properties of message authentication and traceability of fault smart metering. And there are some other useful features in our protocol, such as no need of trust-third party, dynamic users' enrollment and revocation, and complex statistical analysis of the energy use information. The computation cost and communication overhead of our scheme is O(1), which is independent of the user number. The simulation results show that our scheme is efficient.
Mohsen Guizani - One of the best experts on this subject based on the ideXlab platform.
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Blockchain-Based Anonymous Authentication With Selective Revocation for Smart Industrial Applications
IEEE Transactions on Industrial Informatics, 2020Co-Authors: Yanqi Zhao, Lianhai Wang, Mohsen GuizaniAbstract:Personal privacy disclosure is one of the most serious challenges in smart industrial applications. Anonymous authentication is an effective solution to protect personal privacy. However, the existing Anonymous Credential protocols are not perfectly suitablefor smart industrial environments such as smart vehicles in the sense that the Credential revocation issue is not well-solved. In this article, we propose a Blockchain-based Anonymous authentication with Selective revocation for Smart industrial applications (BASS) for smart industrial applications supporting attribute privacy, selective revocation, Credential soundness, and multishowing-unlinkability. Specifically, an efficient selective revocation mechanism is proposed based on dynamic accumulators and the signature algorithm due to Pointcheval and Sanders as the overlay of the BASS. According to the diverse demands of Credential authorities, BASS can selectively provide revocation of Credentials or revocation of users. We extend BASS from single-attribute privacy to multiattribute privacy as well. Finally, we implement a prototype to evaluate the cryptographic core primitives of BASS by deploying smart contracts in Ethereum to demonstrate the validity of BASS in smart industrial applications.
Feng Diao - One of the best experts on this subject based on the ideXlab platform.
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a privacy preserving smart metering scheme using linkable Anonymous Credential
IEEE Transactions on Smart Grid, 2015Co-Authors: Feng Diao, Fangguo Zhang, Xiangguo ChengAbstract:Smart grid, as the next power grid, can efficiently monitor, predicate, and control energy generation/consumption by using the real-time users' electricity information. However, the fine-grained user energy consumption information may reveal the private information of the user. In this paper, we construct a linkable Anonymous Credential protocol based on Camenisch-Lysyanskaya (CL) signature. Then, we propose a privacy preserving smart metering scheme based on the new linkable Anonymous Credential. In addition to providing privacy protection for the user, our protocol also has the security properties of message authentication and traceability of fault smart metering. And there are some other useful features in our protocol, such as no need of trust-third party, dynamic users' enrollment and revocation, and complex statistical analysis of the energy use information. The computation cost and communication overhead of our scheme is O(1), which is independent of the user number. The simulation results show that our scheme is efficient.