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Modifications to the number field sieve. (English) Zbl 0806.11071
The number field sieve, due to Lenstra et al. and Buhler et al., is a routine for factoring integers. The running time of this algorithm is estimated at $$e^{1.923+ \sigma(1) (\log N)^{1/3} (\log\log N)^{2/3}}$$, where $$N$$ is the number to be factored and $$\sigma(1)$$ tends to 0 as $$N\to\infty$$.
The paper gives a brief description of the sieve method and describes a modification which reuses the computations of the initial sieve to reduce the exponent in the running time expression from 1.923 to 1.902.
Furthermore, the same ideas are used to describe a way to precompute tables which are useful in factoring any integers in a large range. Ignoring the cost of the precomputations, an individual integer can be factored in time $$e^{1.639+ \sigma(1) (\log N)^{1/3} (\log\log N)^{2/3}}$$. This substantial decrease in the time for factoring integers could have implications for the choice of prime parameters in cryptography.

##### MSC:
 11Y05 Factorization 11Y16 Number-theoretic algorithms; complexity 94A60 Cryptography
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##### References:
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