32 lines
686 B
C++
32 lines
686 B
C++
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#include "decoding.h"
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void syndrome_decode (bvector&syndrome, gf2m&fld, polynomial& goppa,
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std::vector<polynomial>& sqInv, bvector&ev)
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{
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ev.clear();
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ev.resize (fld.n, 0);
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if (syndrome.zero() ) return;
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polynomial p;
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syndrome.to_poly (p, fld);
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p.inv (goppa, fld); // p=S^-1 mod goppa
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p[1] = fld.add (1, p[1]); //p is now tau
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p.sqrt (sqInv, fld); //tau = sqrt(T+x) mod goppa
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polynomial a, b;
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p.mod_to_fracton (a, b, goppa, fld);
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a.square (fld);
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b.square (fld);
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b.shift (1);
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a.add (b, fld); //new a = a^2 + x b^2
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a.make_monic (fld); //now it is the error locator.
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for (uint i = 0; i < fld.n; ++i) {
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if (0 == a.eval (i, fld) ) ev[i] = 1;
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}
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}
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