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check matrix

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This commit is contained in:
Mirek Kratochvil 2012-04-04 23:01:55 +02:00
parent 171c660d3d
commit 19225c3665
2 changed files with 72 additions and 35 deletions
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4
include/codecrypt.h
View file

@ -120,13 +120,15 @@ public:
void strip();
int degree() const;
bool zero() const;
uint eval (uint, gf2m&) const;
void add (const polynomial&, gf2m&);
void mod (const polynomial&, gf2m&);
void mult (const polynomial&, gf2m&);
polynomial gcd (polynomial, gf2m&);
bool is_irreducible (gf2m&);
bool is_irreducible (gf2m&) const;
void generate_random_irreducible (uint s, gf2m&, prng&);
bool compute_square_root_matrix (std::vector<polynomial>&, gf2m&);
void compute_goppa_check_matrix (matrix&, gf2m&);
};
/*

55
lib/polynomial.cpp
View file

@ -3,14 +3,6 @@
using namespace ccr;
#include <iostream>
using namespace std;
void dump (const polynomial&t)
{
for (uint i = 0; i < t.size(); ++i) cout << t[i] << ' ';
cout << endl;
}
int polynomial::degree() const
{
int r = -1;
@ -45,6 +37,7 @@ void polynomial::mod (const polynomial&f, gf2m&fld)
for (d = degree(); d >= df; --d)
if (item (d) ) {
uint t = fld.mult (item (d), hi);
for (int i = 0; i <= df; ++i)
item (i + d - df) = fld.add (item (i + d - df),
fld.mult (t, f[i]) );
@ -82,7 +75,7 @@ polynomial polynomial::gcd (polynomial b, gf2m&fld)
return polynomial();
}
bool polynomial::is_irreducible (gf2m&fld)
bool polynomial::is_irreducible (gf2m&fld) const
{
//Ben-Or irreducibility test
polynomial xi; //x^(2^i) in our case
@ -103,7 +96,7 @@ bool polynomial::is_irreducible (gf2m&fld)
t.add (xmodf, fld);
t = t.gcd (*this, fld);
if (t.degree() != 0) //gcd(f,x^2^i - x mod f) != 1
if (t.degree() > 0) //gcd(f,x^2^i - x mod f) is polynomial
return false;
}
return true;
@ -191,3 +184,45 @@ for(int c=0;c<d;++c) {\
}
return true;
}
uint polynomial::eval (uint x, gf2m&fld) const
{
uint r = 0;
//horner
for (int i = degree(); i >= 0; --i)
r = fld.add (item (i), fld.mult (r, x) );
return r;
}
void polynomial::compute_goppa_check_matrix (matrix&r, gf2m&fld)
{
if (degree() < 0) return; //wrongly initialized polynomial
uint t = degree();
vector<vector<uint> > yz, h;
uint i, j, k;
yz.resize (t);
h.resize (t);
for (i = 0; i < t; ++i) {
yz[i].resize (fld.n);
h[i].resize (fld.n, 0);
}
//create Y*Z
for (i = 0; i < fld.n; ++i) yz[0][i] = fld.inv (eval (i, fld) );
for (i = 1; i < t; ++i) for (j = 0; j < fld.n; ++j)
yz[i][j] = fld.mult (yz[i-1][j], j);
//X*Y*Z = h
for (i = 0; i < t; ++i)
for (j = 0; j < fld.n; ++j)
for (k = 0; k <= i; ++k)
h[i][j] = fld.add (h[i][j], fld.mult
(yz[k][j],
item (t + k - i) ) );
//now convert to binary
r.resize (fld.n);
for (i = 0; i < fld.n; ++i) {
r[i].resize (fld.m * t, 0);
for (j = 0; j < fld.m * t; ++j)
r[i][j] = (h[j/fld.m][i] >> (j % fld.m) ) & 1;
}
}