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An algorithm for finding square root modulo p

General Mathematics 2021-09-01 v5

Abstract

We propose a novel algorithm for finding square roots modulo p. Although there exists a direct formula to calculate square root of an element modulo prime (3 mod 4), but calculating square root modulo prime (1 mod 4) is non trivial. Tonelli-Shanks algorithm remains the most widely used and probably the fastest when averaged over all primes [19]. This paper proposes a new algorithm for finding square roots modulo all odd primes, which shows improvement over existing method in practical terms although asymptotically gives the same run time as Tonelli-Shanks. Apart from practically efficient computation time, the proposed method does not necessarily require availability of non-residue and can work with `relative non-residue' also. Such `relative non-residues' are much easier to find ( probability 2/3) compared to non-residues ( probability 1/2).

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Cite

@article{arxiv.2008.11814,
  title  = {An algorithm for finding square root modulo p},
  author = {Rajeev Kumar},
  journal= {arXiv preprint arXiv:2008.11814},
  year   = {2021}
}

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19 pages