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Definition
Let G be a cyclic group of order n, and g be a generator for G. Given an element \(y \in G\), the discrete logarithm problem is to find an integer x such that
Background
The discrete logarithm problem has been of particular interest since Diffie and Hellman (Diffie-Hellman Key Agreement) invented a cryptographic system based on the difficulty of finding discrete logarithms (a similar system was created around the same time by Malcolm Williamson at the Government Communications Headquarters (GCHQ) in the UK, but not revealed until years later).
Theory
Any finite group may be used for a Diffie-Hellman system, but some are more secure than others. The main groups used are:
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The multiplicative subgroup of a finite field GF(q), with q a prime or a power of 2
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The points on an...
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Recommended Reading
McCurley KS (1990) The discrete logarithm problem. In: Cryptology and Computational Number Theory, pp. 49–74, AMS, Providence
Odlyzko AM (2000) Discrete logarithms: the past and the future. Design Code Cryptogr 19:129–145
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Gordon, D. (2011). Discrete Logarithm Problem. In: van Tilborg, H.C.A., Jajodia, S. (eds) Encyclopedia of Cryptography and Security. Springer, Boston, MA. https://doi.org/10.1007/978-1-4419-5906-5_445
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DOI: https://doi.org/10.1007/978-1-4419-5906-5_445
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