Pohlig-Hellman (Discrete Logarithm Over Finite Fields Logarithm Calculations)

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Time Complexity

$O({2}^{\sqrt{n}})$, only for primes; does much better for composites

Space Complexity

$O({2}^{\sqrt{n}})$ (though only for primes) words

(A step in the algorithm involves using baby-steps giant-steps to compute discrete logs; the rest of the algorithm (including CRT and repeated powers) isn't as intensive)

Description

Approximate?

Exact

Randomized?

No, deterministic

Model of Computation

Word RAM

Year

1978

Reference

https://dl.acm.org/citation.cfm?id=2269283