Question: Computation of all determinants of sub matrices of a block-matrix in modulo 2

Let A be an nrxnr binary matrix. Suppose that the nxn binary matrix B is obtained from the matrix A using the following code:

n := upperbound(A)[1]/r; 
B := Matrix(n, n, 0); 
for i to n do
 for j to n do 
  B[i, j] := SubMatrix(A, [(i-1)*r+1 .. i*r], [(j-1)*r+1 .. j*r])
 end do;
end do;

In other words, the matrix B is a decomposition of matrix A by rxr binary matrices. In the rest, we want to compute all determinants of the submatrices of B in module 2 as follows: 

u := 1; 
for k to n do
 P := choose(n, k); 
 for i to nops(P) do
  for j to nops(P) do
   W := []; 
   for ii in P[i] do 
    for jj in P[j] do
     W := [op(W), B[ii, jj]] 
    end do 
   end do;
   x := `mod`(Det(convert(blockmatrix(k, k, W), Matrix)), 2); 
  if x = 0 then 
    u := 0;
    i := nops(P)+1;
    j := nops(P)+1;
    k := n+1 
   end if 
  end do 
 end do; 
 unassign('i, j, ii, jj, W, x, P') 
end do

In the last step, we check that if the value of all sub determinants of B in module 2, are non zero, then we announce that the block matrix B is an MDS matrix

if u = 1 then print(MDS) else print(NoMDS) end if

Based on the above description I wrote the following procedure:

restart

with(LinearAlgebra); 
with(linalg, blockmatrix);
with(combinat)

MDS:=proc(A::Matrix,r::integer) 
   local n,B,i,j,u,ii,jj,k,P,W,x; 
   n:=upperbound(A)[1]/r;
   B:=Matrix(n,n,0); 
   for i to n do 
       for j to n do 
	        B[i,j]:=LinearAlgebra:-SubMatrix(A,[(i - 1)*r+1..i*r],[(j - 1)*r+1..j*r]) 
		end do 
	end do; 
	unassign('i,j');
	u:=1; 
	for k to n do
    	P:=combinat:-choose(n,k); 
		for i to nops(P) do
     		for j to nops(P) do
    			W:=[]; 
				for ii in P[i] do
    				for jj in P[j] do 
					    W:=[op(W),B[ii,jj]] 
					end do 
				end do; 
				x:=mod(Det(convert(linalg:-blockmatrix(k,k,W),Matrix)),2);
				if x=0 then 
				   u:=0;
				   i:=nops(P)+1;
				   j:=nops(P)+1;
				   k:=n+1
				end if 
			end do 
		end do; 
		unassign('i,j,ii,jj,W,x,P') 
	end do; 
	if u=1 then print(MDS) else print(NoMDS) end if 
end proc

My problem is that if A is a 64x64 binary matrix and also r=8, then the procedure MDS(A,8) takes 453 seconds to run in my computer (Maple 15 on windows 7 32bit with 4G RAM).

Is it possible to optimize the procedure such that MDS(A,8) takes less than 1 minutes.

Thanks for any help