Two topics in cryptography [Elektronisk resurs] lattice problems and the security of protocols
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Trolin, Mårten, 1974- (författare)
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Håstad, Johan (preses)
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KTH Skolan för datavetenskap och kommunikation (CSC) (utgivare)
- Publicerad: Stockholm : KTH, 2005
- Engelska x, 129
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Serie: Trita-NA, 0348-2952 0348-2952 ; 0504
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- In this thesis we present new results in two areas – cryptographic protocols and lattice problems. • We present a new protocol for electronic cash which is designed to function on hardware with limited computing power. The scheme has provable security properties and low computational requirements, but it still gives a fair amount of privacy. Another feature of the system is that there is no master secret that could be used for counterfeiting money if stolen. • We introduce the notion of hierarchical group signatures. This is a proper generalization of group signatures, which allows multiple group managers organized in a tree with the signers as leaves. For a signer that is a leaf of the subtree of a group manager, the group manager learns which of its children that (perhaps indirectly) manages the signer. We provide definitions for the new notion and construct a scheme that is provably secure given the existence of a family of trapdoor permutations. We also present a construction which is relatively practical, and prove its security in the random oracle model under the strong RSA assumption and the DDH assumption. • We show a weakness in the specification for offline capable EMV payment cards. The weakness, which applies to cards without RSA capability, enables an attacker to duplicate a card and make transactions that cannot be tied to the original card. • We give a method for approximating any n-dimensional lattice with a lattice Λ whose factor group Z n /Λ has n - 1 cycles of equal length with arbitrary precision. We also show that a direct consequence of this is that the Shortest Vector Problem and the Closest Vector Problem cannot be easier for this type of lattices than for general lattices.
Ämnesord
- Natural Sciences (hsv)
- Computer and Information Sciences (hsv)
- Computer Sciences (hsv)
- Naturvetenskap (hsv)
- Data- och informationsvetenskap (hsv)
- Datavetenskap (datalogi) (hsv)
- TECHNOLOGY (svep)
- Information technology (svep)
- Computer science (svep)
- Computer science (svep)
- TEKNIKVETENSKAP (svep)
- Informationsteknik (svep)
- Datavetenskap (svep)
- Datalogi (svep)
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- government publication (marcgt)
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