Abstract
This chapter concludes the theory needed to describe the cryptography in Chap. 9. The key concept is that of the order of a unit b modulo m, and Euler’s Theorem, which places a constraint on the possible values of the order of b. When m is prime, Euler’s Theorem is the same as Fermat’s Theorem, which is given a proof using the Binomial Theorem. The final section describes an efficient algorithm for computing a high power of a number modulo m. This algorithm will have both an obvious use in using the cryptosystems presented in Chaps. 9 and 13 and a less obvious use to help construct cryptosystems in the last section of Chap. 9.
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Childs, L.N. (2019). Orders and Euler’s Theorem. In: Cryptology and Error Correction. Springer Undergraduate Texts in Mathematics and Technology. Springer, Cham. https://doi.org/10.1007/978-3-030-15453-0_8
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DOI: https://doi.org/10.1007/978-3-030-15453-0_8
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