-rw-r--r-- 2417 cryptattacktester-20230614/column_swaps.h raw
#ifndef COLUMN_SWAPS_H
#define COLUMN_SWAPS_H

#include "bigint.h"
#include "permutation.h"
#include "bit_matrix.h"

static bit column_swaps(vector<bit> &s_prime, vector<vector<bit>> &H_prime, vector<vector<bit>> &column_map,
  bigint N,
  bigint K,
  bigint L,
  bigint X,
  bigint Y
)
{
	const bigint R = N - K;
	const bigint KK = K + L;
	const bigint RR = N - KK;

	bit success;

	// swapping X columns while maintaining "systematic form"

	for (bigint t = 0; t < 2; t++)
	{
		// permuting entries in column_map

		permutation pi_KK(KK);
		permutation pi_RR(RR);

		pi_KK.permute(column_map);
		pi_RR.permute(column_map,KK);

		// permuting rows and columns of H_prime

		pi_KK.permute(H_prime);

		for (bigint i = 0; i < KK; i++)
			pi_RR.permute(H_prime.at(i),L);

		// permuting rows of s_prime

		pi_RR.permute(s_prime,L);

		if (t == 1)
			break;

		// gaussian elimination on x rows

		vector<vector<bit>> m;

		for (bigint i = 0; i < KK + X; i++)
			m.push_back(bit_vector_extract(H_prime.at(i), L, L + X));

		m.push_back(bit_vector_extract(s_prime, L, L + X));

		vector<vector<bit>> pivots(0);
		success = bit_matrix_reduced_echelon(pivots, m, Y);

		for (bigint i = 0; i < X; i++)
			s_prime.at(i + L) = m.back().at(i);

		m.pop_back();

		for (bigint i = 0; i < KK + X; i++)
		for (bigint j = 0; j < X; j++)
			H_prime.at(i).at(j + L) = m.at(i).at(j);

		// swapping columns
	
		for (bigint i = 0; i < X; i++)
		{
			H_prime.at(KK + i)    = ram_read_write(H_prime,    i, Y, pivots.at(i), H_prime.at(KK + i));
			column_map.at(KK + i) = ram_read_write(column_map, i, Y, pivots.at(i), column_map.at(KK + i));
		}

		// maintaining systematic form

		for (bigint x = 0; x < X; x++)
		for (bigint i = 0; i < KK; i++)	
		{
			for (bigint j = 0;   j < L; j++) H_prime.at(i).at(j) ^= H_prime.at(i).at(x + L) & H_prime.at(x + KK).at(j);	
			for (bigint j = L+X; j < R; j++) H_prime.at(i).at(j) ^= H_prime.at(i).at(x + L) & H_prime.at(x + KK).at(j);	
		}

		for (bigint x = 0; x < X; x++)
		{
			for (bigint j = 0;   j < L; j++) s_prime.at(j) ^= s_prime.at(x + L) & H_prime.at(x + KK).at(j);	
			for (bigint j = L+X; j < R; j++) s_prime.at(j) ^= s_prime.at(x + L) & H_prime.at(x + KK).at(j);	
		}

		for (bigint x = KK; x < KK + X; x++)
		{
	 		for (bigint j = 0;   j < L; j++) H_prime.at(x).at(j) = bit(0);
	 		for (bigint j = L+X; j < R; j++) H_prime.at(x).at(j) = bit(0);
		}
	}

	return success;
}

#endif