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An Efficient Offline Electronic Cash System Based On The Representation Problem
, 1993
"... We present a new offline electronic cash system based on a problem, called the representation problem, of which little use has been made in literature thus far. Our system is the first to be based entirely on discrete logarithms. Using the representation problem as a basic concept, some technique ..."
Abstract

Cited by 151 (3 self)
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We present a new offline electronic cash system based on a problem, called the representation problem, of which little use has been made in literature thus far. Our system is the first to be based entirely on discrete logarithms. Using the representation problem as a basic concept, some techniques are introduced that enable us to construct protocols for withdrawal and payment that do not use the cut and choose methodology of earlier systems. As a consequence, our cash system is much more efficient in both computation and communication complexity than previously proposed systems. Another
Cascade Ciphers: The Importance of Being First
, 1993
"... The security of cascade ciphers, in which by definition the keys of the component ciphers are independent, is considered. It is shown by a counterexample that the intuitive result, formally stated and proved in the literature, that a cascade is at least as strong as the strongest component cipher, ..."
Abstract

Cited by 31 (3 self)
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The security of cascade ciphers, in which by definition the keys of the component ciphers are independent, is considered. It is shown by a counterexample that the intuitive result, formally stated and proved in the literature, that a cascade is at least as strong as the strongest component cipher, requires the uninterestingly restrictive assumption that the enemy cannot exploit information about the plaintext statistics. It is proved, for very general notions of breaking a cipher and of problem difficulty, that a cascade is at least as difficult to break as the first component cipher. A consequence of this result is that, if the ciphers commute, then a cascade is at least as difficult to break as the mostdifficulttobreak component cipher, i.e., the intuition that a cryptographic chain is at least as strong as its strongest link is then provably correct. It is noted that additive stream ciphers do commute, and this fact is used to suggest a strategy for designing secure practical ci...