The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Tomoyuki Yamakami - One of the best experts on this subject based on the ideXlab platform.
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Computational Indistinguishability Between Quantum States and Its Cryptographic Application
Journal of Cryptology, 2012Co-Authors: Akinori Kawachi, Takeshi Koshiba, Harumichi Nishimura, Tomoyuki YamakamiAbstract:We introduce a computational problem of distinguishing between two specific quantum states as a new Cryptographic problem to design a quantum Cryptographic scheme that is “secure” against any polynomial-time quantum adversary. Our problem, QSCD_ff, is to distinguish between two types of random coset states with a hidden permutation over the symmetric group of finite degree. This naturally generalizes the commonly-used distinction problem between two probability distributions in computational cryptography. As our major contribution, we show that QSCD_ff has three properties of Cryptographic interest: (i) QSCD_ff has a trapdoor; (ii) the average-case hardness of QSCD_ff coincides with its worst-case hardness; and (iii) QSCD_ff is computationally at least as hard as the graph automorphism problem in the worst case. These Cryptographic properties enable us to construct a quantum public-key cryptosystem which is likely to withstand any chosen plaintext attack of a polynomial-time quantum adversary. We further discuss a generalization of QSCD_ff, called QSCD_cyc, and introduce a multi-bit encryption scheme that relies on similar Cryptographic properties of QSCD_cyc.
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Computational Indistinguishability Between Quantum States and Its Cryptographic Application
Journal of Cryptology, 2011Co-Authors: Akinori Kawachi, Takeshi Koshiba, Harumichi Nishimura, Tomoyuki YamakamiAbstract:We introduce a computational problem of distinguishing between two specific quantum states as a new Cryptographic problem to design a quantum Cryptographic scheme that is "secure" against any polynomial-time quantum adversary. Our problem, QSCDff, is to distinguish between two types of random coset states with a hidden permutation over the symmetric group of finite degree. This naturally generalizes the commonly-used distinction problem between two probability distributions in computational cryptography. As our major contribution, we show that QSCDff has three properties of Cryptographic interest: (i) QSCDff has a trapdoor; (ii) the average-case hardness of QSCDff coincides with its worst-case hardness; and (iii) QSCDff is computationally at least as hard as the graph automorphism problem in the worst case. These Cryptographic properties enable us to construct a quantum public-key cryptosystem, which is likely to withstand any chosen plaintext attack of a polynomial-time quantum adversary. We further discuss a generalization of QSCDff, called QSCDcyc, and introduce a multi-bit encryption scheme that relies on similar Cryptographic properties of QSCDcyc.Comment: 24 pages, 2 figures. We improved presentation, and added more detail proofs and follow-up of recent wor
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computational indistinguishability between quantum states and its Cryptographic Application
Theory and Application of Cryptographic Techniques, 2005Co-Authors: Akinori Kawachi, Takeshi Koshiba, Harumichi Nishimura, Tomoyuki YamakamiAbstract:We introduce a problem of distinguishing between two quantum states as a new underlying problem to build a computational Cryptographic scheme that is ”secure” against quantum adversary. Our problem is a natural generalization of the distinguishability problem between two probability distributions, which are commonly used in computational cryptography. More precisely, our problem QSCDff is the computational distinguishability problem between two types of random coset states with a hidden permutation over the symmetric group. We show that (i) QSCDff has the trapdoor property; (ii) the average-case hardness of QSCDff coincides with its worst-case hardness; and (iii) QSCDff is at least as hard in the worst case as the graph automorphism problem. Moreover, we show that QSCDff cannot be efficiently solved by any quantum algorithm that naturally extends Shor's factorization algorithm. These Cryptographic properties of QSCDff enable us to construct a public-key cryptosystem, which is likely to withstand any attack of a polynomial-time quantum adversary.
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EUROCRYPT - Computational indistinguishability between quantum states and its Cryptographic Application
Lecture Notes in Computer Science, 2005Co-Authors: Akinori Kawachi, Takeshi Koshiba, Harumichi Nishimura, Tomoyuki YamakamiAbstract:We introduce a problem of distinguishing between two quantum states as a new underlying problem to build a computational Cryptographic scheme that is ”secure” against quantum adversary. Our problem is a natural generalization of the distinguishability problem between two probability distributions, which are commonly used in computational cryptography. More precisely, our problem QSCDff is the computational distinguishability problem between two types of random coset states with a hidden permutation over the symmetric group. We show that (i) QSCDff has the trapdoor property; (ii) the average-case hardness of QSCDff coincides with its worst-case hardness; and (iii) QSCDff is at least as hard in the worst case as the graph automorphism problem. Moreover, we show that QSCDff cannot be efficiently solved by any quantum algorithm that naturally extends Shor's factorization algorithm. These Cryptographic properties of QSCDff enable us to construct a public-key cryptosystem, which is likely to withstand any attack of a polynomial-time quantum adversary.
Mayank Varia - One of the best experts on this subject based on the ideXlab platform.
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obfuscation of hyperplane membership
Theory of Cryptography Conference, 2010Co-Authors: Ran Canetti, Guy N Rothblum, Mayank VariaAbstract:Previous work on program obfuscation gives strong negative results for general-purpose obfuscators, and positive results for obfuscating simple functions such as equality testing (point functions). In this work, we construct an obfuscator for a more complex algebraic functionality: testing for membership in a hyperplane (of constant dimension). We prove the security of the obfuscator under a new strong variant of the Decisional Diffie-Hellman assumption. Finally, we show a Cryptographic Application of the new obfuscator to digital signatures.
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TCC - Obfuscation of hyperplane membership
Theory of Cryptography, 2010Co-Authors: Ran Canetti, Guy N Rothblum, Mayank VariaAbstract:Previous work on program obfuscation gives strong negative results for general-purpose obfuscators, and positive results for obfuscating simple functions such as equality testing (point functions). In this work, we construct an obfuscator for a more complex algebraic functionality: testing for membership in a hyperplane (of constant dimension). We prove the security of the obfuscator under a new strong variant of the Decisional Diffie-Hellman assumption. Finally, we show a Cryptographic Application of the new obfuscator to digital signatures.
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Studies in program obfuscation
2010Co-Authors: Ran Canetti, Mayank VariaAbstract:Program obfuscation is the software analog to the problem of tamper-proofing hardware. The goal of program obfuscation is to construct a compiler, called an "obfuscator," that garbles the code of a computer program while maintaining its functionality. Commercial products exist to perform this procedure, but they do not provide a rigorous security guarantee. Over the past decade, program obfuscation has been studied by the theoretical cryptography community, where rigorous definitions of security have been proposed and obfuscators have been constructed for sonic, families of programs. This thesis presents three contributions based on the virtual black-box security definition of Barak et al [10]. First, we show tight connections between obfuscation and symmetric-key encryption. Specifically, obfuscation can be used to construct an encryption scheme with strong leakage resilience and key-dependent message security. The converse is also true, and these connections scale with the level of security desired. As a result, the known constructions and impossibility results for each primitive carry over to the other. Second, we present two new security definitions that augment the virtual black-box property to incorporate non-malleability. The virtual black-box definition does not prevent an adversary from modifying an obfuscated program intelligently. By contrast, our new definitions provide software with the same security guarantees as tamper-proof and tamper-evident hardware, respectively. The first definition prohibits tampering, and the second definition requires that tampering is detectable after the fact. We construct non-malleable obfuscators of both flavors for some program families of interest. Third, we present an obfuscator for programs that test for membership in a hyperplane. This generalizes prior works that obfuscate equality testing. We prove the security of the obfuscator under a new strong variant of the Decisional Diffie-Hellman assumption that holds in the generic group model. Additionally, we show a Cryptographic Application of the new obfuscator to leakage- resilient one-time digital signatures. The thesis also includes a survey of the prior results in the field. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)
Akinori Kawachi - One of the best experts on this subject based on the ideXlab platform.
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Computational Indistinguishability Between Quantum States and Its Cryptographic Application
Journal of Cryptology, 2012Co-Authors: Akinori Kawachi, Takeshi Koshiba, Harumichi Nishimura, Tomoyuki YamakamiAbstract:We introduce a computational problem of distinguishing between two specific quantum states as a new Cryptographic problem to design a quantum Cryptographic scheme that is “secure” against any polynomial-time quantum adversary. Our problem, QSCD_ff, is to distinguish between two types of random coset states with a hidden permutation over the symmetric group of finite degree. This naturally generalizes the commonly-used distinction problem between two probability distributions in computational cryptography. As our major contribution, we show that QSCD_ff has three properties of Cryptographic interest: (i) QSCD_ff has a trapdoor; (ii) the average-case hardness of QSCD_ff coincides with its worst-case hardness; and (iii) QSCD_ff is computationally at least as hard as the graph automorphism problem in the worst case. These Cryptographic properties enable us to construct a quantum public-key cryptosystem which is likely to withstand any chosen plaintext attack of a polynomial-time quantum adversary. We further discuss a generalization of QSCD_ff, called QSCD_cyc, and introduce a multi-bit encryption scheme that relies on similar Cryptographic properties of QSCD_cyc.
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Computational Indistinguishability Between Quantum States and Its Cryptographic Application
Journal of Cryptology, 2011Co-Authors: Akinori Kawachi, Takeshi Koshiba, Harumichi Nishimura, Tomoyuki YamakamiAbstract:We introduce a computational problem of distinguishing between two specific quantum states as a new Cryptographic problem to design a quantum Cryptographic scheme that is "secure" against any polynomial-time quantum adversary. Our problem, QSCDff, is to distinguish between two types of random coset states with a hidden permutation over the symmetric group of finite degree. This naturally generalizes the commonly-used distinction problem between two probability distributions in computational cryptography. As our major contribution, we show that QSCDff has three properties of Cryptographic interest: (i) QSCDff has a trapdoor; (ii) the average-case hardness of QSCDff coincides with its worst-case hardness; and (iii) QSCDff is computationally at least as hard as the graph automorphism problem in the worst case. These Cryptographic properties enable us to construct a quantum public-key cryptosystem, which is likely to withstand any chosen plaintext attack of a polynomial-time quantum adversary. We further discuss a generalization of QSCDff, called QSCDcyc, and introduce a multi-bit encryption scheme that relies on similar Cryptographic properties of QSCDcyc.Comment: 24 pages, 2 figures. We improved presentation, and added more detail proofs and follow-up of recent wor
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computational indistinguishability between quantum states and its Cryptographic Application
Theory and Application of Cryptographic Techniques, 2005Co-Authors: Akinori Kawachi, Takeshi Koshiba, Harumichi Nishimura, Tomoyuki YamakamiAbstract:We introduce a problem of distinguishing between two quantum states as a new underlying problem to build a computational Cryptographic scheme that is ”secure” against quantum adversary. Our problem is a natural generalization of the distinguishability problem between two probability distributions, which are commonly used in computational cryptography. More precisely, our problem QSCDff is the computational distinguishability problem between two types of random coset states with a hidden permutation over the symmetric group. We show that (i) QSCDff has the trapdoor property; (ii) the average-case hardness of QSCDff coincides with its worst-case hardness; and (iii) QSCDff is at least as hard in the worst case as the graph automorphism problem. Moreover, we show that QSCDff cannot be efficiently solved by any quantum algorithm that naturally extends Shor's factorization algorithm. These Cryptographic properties of QSCDff enable us to construct a public-key cryptosystem, which is likely to withstand any attack of a polynomial-time quantum adversary.
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EUROCRYPT - Computational indistinguishability between quantum states and its Cryptographic Application
Lecture Notes in Computer Science, 2005Co-Authors: Akinori Kawachi, Takeshi Koshiba, Harumichi Nishimura, Tomoyuki YamakamiAbstract:We introduce a problem of distinguishing between two quantum states as a new underlying problem to build a computational Cryptographic scheme that is ”secure” against quantum adversary. Our problem is a natural generalization of the distinguishability problem between two probability distributions, which are commonly used in computational cryptography. More precisely, our problem QSCDff is the computational distinguishability problem between two types of random coset states with a hidden permutation over the symmetric group. We show that (i) QSCDff has the trapdoor property; (ii) the average-case hardness of QSCDff coincides with its worst-case hardness; and (iii) QSCDff is at least as hard in the worst case as the graph automorphism problem. Moreover, we show that QSCDff cannot be efficiently solved by any quantum algorithm that naturally extends Shor's factorization algorithm. These Cryptographic properties of QSCDff enable us to construct a public-key cryptosystem, which is likely to withstand any attack of a polynomial-time quantum adversary.
Adam Smith - One of the best experts on this subject based on the ideXlab platform.
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fuzzy extractors how to generate strong keys from biometrics and other noisy data
arXiv: Cryptography and Security, 2006Co-Authors: Yevgeniy Dodis, Leonid Reyzin, Rafail Ostrovsky, Adam SmithAbstract:We provide formal definitions and efficient secure techniques for - turning noisy information into keys usable for any Cryptographic Application, and, in particular, - reliably and securely authenticating biometric data. Our techniques apply not just to biometric information, but to any keying material that, unlike traditional Cryptographic keys, is (1) not reproducible precisely and (2) not distributed uniformly. We propose two primitives: a "fuzzy extractor" reliably extracts nearly uniform randomness R from its input; the extraction is error-tolerant in the sense that R will be the same even if the input changes, as long as it remains reasonably close to the original. Thus, R can be used as a key in a Cryptographic Application. A "secure sketch" produces public information about its input w that does not reveal w, and yet allows exact recovery of w given another value that is close to w. Thus, it can be used to reliably reproduce error-prone biometric inputs without incurring the security risk inherent in storing them. We define the primitives to be both formally secure and versatile, generalizing much prior work. In addition, we provide nearly optimal constructions of both primitives for various measures of ``closeness'' of input data, such as Hamming distance, edit distance, and set difference.
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fuzzy extractors how to generate strong keys from biometrics and other noisy data
Theory and Application of Cryptographic Techniques, 2004Co-Authors: Yevgeniy Dodis, Leonid Reyzin, Adam SmithAbstract:We provide formal definitions and efficient secure techniques for turning biometric information into keys usable for any Cryptographic Application, and reliably and securely authenticating biometric data.
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fuzzy extractors how to generate strong keys from biometrics and other noisy data
Lecture Notes in Computer Science, 2004Co-Authors: Yevgeniy Dodis, Leonid Reyzin, Adam SmithAbstract:We provide formal definitions and efficient secure techniques for - turning biometric information into keys usable for any Cryptographic Application, and - reliably and securely authenticating biometric data. Our techniques apply not just to biometric information, but to any keying material that, unlike traditional Cryptographic keys, is (1) not reproducible precisely and (2) not distributed uniformly. We propose two primitives: a fuzzy extractor extracts nearly uniform randomness R from its biometric input; the extraction is error-tolerant in the sense that R will be the same even if the input changes, as long as it remains reasonably close to the original. Thus, R can be used as a key in any Cryptographic Application. A secure sketch produces public information about its biometric input w that does not reveal w, and yet allows exact recovery of w given another value that is close to w. Thus, it can be used to reliably reproduce error-prone biometric inputs without incurring the security risk inherent in storing them. In addition to formally introducing our new primitives, we provide nearly optimal constructions of both primitives for various measures of closeness of input data, such as Hamming distance, edit distance, and set difference.
Ran Canetti - One of the best experts on this subject based on the ideXlab platform.
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obfuscation of hyperplane membership
Theory of Cryptography Conference, 2010Co-Authors: Ran Canetti, Guy N Rothblum, Mayank VariaAbstract:Previous work on program obfuscation gives strong negative results for general-purpose obfuscators, and positive results for obfuscating simple functions such as equality testing (point functions). In this work, we construct an obfuscator for a more complex algebraic functionality: testing for membership in a hyperplane (of constant dimension). We prove the security of the obfuscator under a new strong variant of the Decisional Diffie-Hellman assumption. Finally, we show a Cryptographic Application of the new obfuscator to digital signatures.
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TCC - Obfuscation of hyperplane membership
Theory of Cryptography, 2010Co-Authors: Ran Canetti, Guy N Rothblum, Mayank VariaAbstract:Previous work on program obfuscation gives strong negative results for general-purpose obfuscators, and positive results for obfuscating simple functions such as equality testing (point functions). In this work, we construct an obfuscator for a more complex algebraic functionality: testing for membership in a hyperplane (of constant dimension). We prove the security of the obfuscator under a new strong variant of the Decisional Diffie-Hellman assumption. Finally, we show a Cryptographic Application of the new obfuscator to digital signatures.
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Studies in program obfuscation
2010Co-Authors: Ran Canetti, Mayank VariaAbstract:Program obfuscation is the software analog to the problem of tamper-proofing hardware. The goal of program obfuscation is to construct a compiler, called an "obfuscator," that garbles the code of a computer program while maintaining its functionality. Commercial products exist to perform this procedure, but they do not provide a rigorous security guarantee. Over the past decade, program obfuscation has been studied by the theoretical cryptography community, where rigorous definitions of security have been proposed and obfuscators have been constructed for sonic, families of programs. This thesis presents three contributions based on the virtual black-box security definition of Barak et al [10]. First, we show tight connections between obfuscation and symmetric-key encryption. Specifically, obfuscation can be used to construct an encryption scheme with strong leakage resilience and key-dependent message security. The converse is also true, and these connections scale with the level of security desired. As a result, the known constructions and impossibility results for each primitive carry over to the other. Second, we present two new security definitions that augment the virtual black-box property to incorporate non-malleability. The virtual black-box definition does not prevent an adversary from modifying an obfuscated program intelligently. By contrast, our new definitions provide software with the same security guarantees as tamper-proof and tamper-evident hardware, respectively. The first definition prohibits tampering, and the second definition requires that tampering is detectable after the fact. We construct non-malleable obfuscators of both flavors for some program families of interest. Third, we present an obfuscator for programs that test for membership in a hyperplane. This generalizes prior works that obfuscate equality testing. We prove the security of the obfuscator under a new strong variant of the Decisional Diffie-Hellman assumption that holds in the generic group model. Additionally, we show a Cryptographic Application of the new obfuscator to leakage- resilient one-time digital signatures. The thesis also includes a survey of the prior results in the field. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)