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D.12.3.32 factorLenstraECM
Procedure from library crypto.lib (see crypto_lib).
- Usage:
- factorLenstraECM(N,S,B); optional: factorLenstraECM(N,S,B,d);
d+1 the number of loops in the algorithm (default d=0)
- Return:
- a factor of N or the message no factor found
- Note:
- - computes a factor of N using Lenstra's ECM factorization
- the idea is that the fact that N is not prime is detected using
the operations on the elliptic curve
- is similarly to Pollard's p-1-factorization
Example:
| | LIB "crypto.lib";
list L=primList(1000);
factorLenstraECM(181*32003,L,10,5);
==> 181
bigint h=10;
h=h^30+25;
factorLenstraECM(h,L,4,3);
==> 13
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