public Matrix GetBasisOfWeight(Matrix B, int weight, int num)
{
Matrix res = new Matrix(), Bchange, B_copy = new Matrix(B);
while (res.size[0] < num)
{
Bchange = MatrixFuncs.GenNoise(B.size[0]);
B_copy = Bchange * B_copy;
for (int i = 0; i < B.size[0]; ++i)
{
if (Common.wt(B_copy.data[i]) == weight)
{
if (MatrixFuncs.Gauss(res & new Vector(B_copy.data[i])) == res.size[0] + 1)
{
;
}
res &= new Vector(B_copy.data[i]);
}
if (res.size[0] == num)
{
break;
}
}
}
return(res);
}
public static Matrix operator *(Code C1, Code C2)
{
if (C1.n != C2.n)
{
return(null);
}
List <List <int> > new_basis = new List <List <int> >();
List <int> item = new List <int>();
for (int i = 0; i < C1.k; ++i)
{
for (int j = 0; j < C2.k; ++j)
{
item = new List <int>();
for (int s = 0; s < C2.n; ++s)
{
item.Add(C1.G.data[i][s] * C2.G.data[j][s]);
}
new_basis.Add(item);
}
}
Matrix res = new Matrix(new_basis);
MatrixFuncs.Gauss(res);
return(res);
}
// Generate a random invertible matrix
public static Matrix GenNoise(int size)
{
Matrix res = new Matrix(size, size);
do
{
for (int i = 0; i < size; ++i)
{
for (int j = 0; j < size; ++j)
{
res.data[i][j] = Common.GetRand() & 1;
}
}
} while (MatrixFuncs.Gauss(new Matrix(res)) < size);
return(res);
}
public double AttackRM(out Matrix N1, out Matrix P1)
{
int k = Gp.size[0], n = Gp.size[1];
N1 = new Matrix(k, k); P1 = new Matrix(n, n);
Code code = new Code(Gp); Code Gp_reduced;
// Compute r, m
int r = -1, m = (int)Math.Log(n, 2), k1 = 0;
while (k1 < k)
{
++r;
k1 += Common.C(m, r);
}
RM rm = new RM(r, m);
Stopwatch t = new Stopwatch(); t.Start();
// Reduction
//2 * r >= m => reduction on dual code
if (2 * r < m || m - r == 1)
{
Gp_reduced = new Code(code.G);
}
else
{
Gp_reduced = new Code(code.H);
r = m - r - 1;
}
while (r > 1)
{
Gp_reduced = AttackFuncs.Reduction(Gp_reduced, r, m);
--r;
}
// Matrix P
Matrix Tmp; int idx = -1;
Vector e = new Vector(Enumerable.Repeat(1, n).ToList());
do
{
++idx;
Tmp = (new Matrix(Gp_reduced.G) - idx) & e;
}while (MatrixFuncs.Gauss(Tmp) < m + 1);
Tmp = Gp_reduced.G; Tmp -= idx; Matrix RM_1 = (new RM(1, m)).G -= 0;
IEnumerable <int> tmp1, tmp2;
Matrix P1_inv = new Matrix(n, n);
for (int j = 0; j < n; ++j)
{
tmp1 = Tmp.data.Select(x => x[j]);
for (int jj = 0; jj < n; ++jj)
{
tmp2 = RM_1.data.Select(x => x[jj]);
if (tmp1.SequenceEqual(tmp2))
{
P1.data[jj][j] = 1;
P1_inv.data[j][jj] = 1;
break;
}
}
}
// Matrix N
code.G = code.G * P1_inv;
N1 = MatrixFuncs.Transp(MatrixFuncs.SolveEq(MatrixFuncs.Transp(rm.G), MatrixFuncs.Transp(code.G)));
t.Stop();
return(t.ElapsedMilliseconds / 1000.00);
}
// Reduction on r-parameter (for RM-codes)
public static Code Reduction(Code code_r, int r, int m)
{
int k = code_r.G.size[0], n = code_r.G.size[1];
Matrix res = new Matrix();
int sz = code_r.G.size[0] - Common.C(m, r);
Vector x; List <int> ind_f = new List <int>(); List <List <int> > ind_sets = new List <List <int> >();
int w = 1 << (m - r), wmin = (1 << r) - 1;
Matrix H_short;
while (res.size[0] < sz)
{
x = Code.FindWeight_simple(code_r.G, w);
H_short = new Matrix(n - k, n - w);
int c = 0; ind_f.Clear();
for (int j = 0; j < n; ++j)
{
if (x.data[j] == 0)
{
for (int i = 0; i < code_r.H.size[0]; ++i)
{
H_short.data[i][c] = code_r.H.data[i][j];
}
ind_f.Add(j);
++c;
}
}
MatrixFuncs.Gauss(H_short); //выделяем максимальную л.н. подсистему
Ind_set(H_short, ind_f, r, m, (long)n, ind_sets);
List <Vector> vecs = new List <Vector>();
for (int i = 0; i < wmin; ++i)
{
vecs.Add(new Vector(n));
for (int j = 0; j < w; j++)
{
vecs[i].data[ind_sets[i][j]] = 1;
}
}
for (int i = 0; i < wmin; ++i)
{
for (int j = 0; j < n; j++)
{
if (x.data[j] != 0)
{
vecs[i].data[j] = 1;
}
}
if (code_r.IsCodeWord(vecs[i]))
{
if (res.size[0] == 0 || MatrixFuncs.Gauss(res & vecs[i]) == res.size[0] + 1)
{
res &= vecs[i];
}
}
if (res.size[0] == sz)
{
return(new Code(res));
}
}
ind_f.Clear();
}
return(new Code(res));
}
