/*
  This file is for public-key generation
*/
// 20221231 djb: remove unused min definition
// 20221231 djb: more 0 initialization to clarify data flow; tnx thom wiggers
// 20221230 djb: add linker lines

// linker define pk_gen
// linker use fft vec_inv vec_mul

#include "pk_gen.h"

#include "controlbits.h"
#include "uint64_sort.h"
#include "transpose.h"
#include "params.h"
#include "benes.h"
#include "util.h"
#include "fft.h"
#include "crypto_declassify.h"
#include "crypto_uint64.h"

static crypto_uint64 uint64_is_equal_declassify(uint64_t t,uint64_t u)
{
  crypto_uint64 mask = crypto_uint64_equal_mask(t,u);
  crypto_declassify(&mask,sizeof mask);
  return mask;
}

static crypto_uint64 uint64_is_zero_declassify(uint64_t t)
{
  crypto_uint64 mask = crypto_uint64_zero_mask(t);
  crypto_declassify(&mask,sizeof mask);
  return mask;
}

#include <stdint.h>

static void de_bitslicing(uint64_t * out, const vec in[][GFBITS])
{
	int i, j, r;

	for (i = 0; i < (1 << GFBITS); i++)
		out[i] = 0 ;

	for (i = 0; i < 128; i++)
	for (j = GFBITS-1; j >= 0; j--)
	for (r = 0; r < 64; r++) 
	{ 
		out[i*64 + r] <<= 1; 
		out[i*64 + r] |= (in[i][j] >> r) & 1; 
	}
}

static void to_bitslicing_2x(vec out0[][GFBITS], vec out1[][GFBITS], const uint64_t * in)
{
	int i, j, r;

	for (i = 0; i < 128; i++)
	{
		for (j = 0;j < GFBITS;++j) out0[i][j] = out1[i][j] = 0;

		for (j = GFBITS-1; j >= 0; j--)
		for (r = 63; r >= 0; r--)
		{
			out1[i][j] <<= 1;
			out1[i][j] |= (in[i*64 + r] >> (j + GFBITS)) & 1;
		}
        
		for (j = GFBITS-1; j >= 0; j--)
		for (r = 63; r >= 0; r--)
		{
			out0[i][GFBITS-1-j] <<= 1;
			out0[i][GFBITS-1-j] |= (in[i*64 + r] >> j) & 1;
		}
	}
}

/* return number of trailing zeros of in */
static inline int ctz(uint64_t in)
{
	int i, b, m = 0, r = 0;

	for (i = 0; i < 64; i++)
	{
		b = (in >> i) & 1;
		m |= b;
		r += (m^1) & (b^1);
	}

	return r;
}

static inline uint64_t same_mask(uint16_t x, uint16_t y)
{
        uint64_t mask;

        mask = x ^ y;
        mask -= 1;
        mask >>= 63;
        mask = -mask;

        return mask;
}

static int mov_columns(uint64_t mat[][ ((SYS_N + 63) / 64) ], int16_t * pi, uint64_t * pivots)
{
	int i, j, k, s, block_idx, row;
	uint64_t buf[64], ctz_list[32], t, d, mask, one = 1; 
       
	row = PK_NROWS - 32;
	block_idx = row/64;

	// extract the 32x64 matrix

	for (i = 0; i < 32; i++)
		buf[i] = mat[ row + i ][ block_idx ];
        
	// compute the column indices of pivots by Gaussian elimination.
	// the indices are stored in ctz_list

	*pivots = 0;

	for (i = 0; i < 32; i++)
	{
		t = buf[i];
		for (j = i+1; j < 32; j++)
			t |= buf[j];

		if (uint64_is_zero_declassify(t)) return -1; // return if buf is not full rank

		ctz_list[i] = s = ctz(t);
		*pivots |= one << ctz_list[i];

		for (j = i+1; j < 32; j++) { mask = (buf[i] >> s) & 1; mask -= 1;    buf[i] ^= buf[j] & mask; }
		for (j = i+1; j < 32; j++) { mask = (buf[j] >> s) & 1; mask = -mask; buf[j] ^= buf[i] & mask; }
	}
   
	// updating permutation
  
	for (j = 0;   j < 32; j++)
	for (k = j+1; k < 64; k++)
	{
			d = pi[ row + j ] ^ pi[ row + k ];
			d &= same_mask(k, ctz_list[j]);
			pi[ row + j ] ^= d;
			pi[ row + k ] ^= d;
	}
   
	// moving columns of mat according to the column indices of pivots

	for (i = 0; i < PK_NROWS; i++)
	{
		t = mat[ i ][ block_idx ];
                 
		for (j = 0; j < 32; j++)
		{
			d  = t >> j;
			d ^= t >> ctz_list[j];
			d &= 1;
        
			t ^= d << ctz_list[j];
			t ^= d << j;
		}
                
		mat[ i ][ block_idx ] = t;
	}

	return 0;
}

int pk_gen(unsigned char * pk, const unsigned char * irr, uint32_t * perm, int16_t * pi, uint64_t * pivots)
{
	const int nblocks_H = (SYS_N + 63) / 64;
	const int nblocks_I = (PK_NROWS + 63) / 64;
	int tail = PK_NROWS % 64;

	int i, j, k;
	int row, c;
	
	uint64_t mat[ PK_NROWS ][ nblocks_H ];

	uint64_t mask;	

	vec irr_int[2][ GFBITS ];

	vec consts[ 128 ][ GFBITS ];
	vec eval[ 128 ][ GFBITS ];
	vec prod[ 128 ][ GFBITS ];
	vec tmp[ GFBITS ];

	uint64_t list[1 << GFBITS];

	// compute the inverses 

	irr_load(irr_int, irr);

	fft(eval, irr_int);

	vec_copy(prod[0], eval[0]);

	for (i = 1; i < 128; i++)
		vec_mul(prod[i], prod[i-1], eval[i]);

	vec_inv(tmp, prod[127]);

	for (i = 126; i >= 0; i--)
	{
		vec_mul(prod[i+1], prod[i], tmp);
		vec_mul(tmp, tmp, eval[i+1]);
	}

	vec_copy(prod[0], tmp);

	// fill matrix 

	de_bitslicing(list, prod);

	for (i = 0; i < (1 << GFBITS); i++)
	{	
		list[i] <<= GFBITS;
		list[i] |= i;	
		list[i] |= ((uint64_t) perm[i]) << 31;
	}

	uint64_sort(list, 1 << GFBITS);

	for (i = 1; i < (1 << GFBITS); i++)
		if (uint64_is_equal_declassify(list[i-1] >> 31,list[i] >> 31))
			return -1;

	to_bitslicing_2x(consts, prod, list);

	for (i = 0; i < (1 << GFBITS); i++)
		pi[i] = list[i] & GFMASK;

	for (j = 0; j < nblocks_H; j++)
	for (k = 0; k < GFBITS; k++)
		mat[ k ][ j ] = prod[ j ][ k ];

	for (i = 1; i < SYS_T; i++)
	for (j = 0; j < nblocks_H; j++)
	{
		vec_mul(prod[j], prod[j], consts[j]);

		for (k = 0; k < GFBITS; k++)
			mat[ i*GFBITS + k ][ j ] = prod[ j ][ k ];
	}

	// gaussian elimination

	for (row = 0; row < PK_NROWS; row++)
	{
		i = row >> 6;
		j = row & 63;

		if (row == PK_NROWS - 32)
		{
			if (mov_columns(mat, pi, pivots))
				return -1;
		}

		for (k = row + 1; k < PK_NROWS; k++)
		{
			mask = mat[ row ][ i ] >> j;
			mask &= 1;
			mask -= 1;

			for (c = 0; c < nblocks_H; c++)
				mat[ row ][ c ] ^= mat[ k ][ c ] & mask;
		}

                if ( uint64_is_zero_declassify((mat[ row ][ i ] >> j) & 1) ) // return if not systematic
		{
			return -1;
		}

		for (k = 0; k < row; k++)
		{
			mask = mat[ k ][ i ] >> j;
			mask &= 1;
			mask = -mask;

			for (c = 0; c < nblocks_H; c++)
				mat[ k ][ c ] ^= mat[ row ][ c ] & mask;
		}

		for (k = row+1; k < PK_NROWS; k++)
		{
			mask = mat[ k ][ i ] >> j;
			mask &= 1;
			mask = -mask;

			for (c = 0; c < nblocks_H; c++)
				mat[ k ][ c ] ^= mat[ row ][ c ] & mask;
		}
	}

	for (i = 0; i < PK_NROWS; i++)	
	{
		store_i(pk, mat[i][ nblocks_I-1 ] >> tail, (64-tail)/8);
		pk += (64-tail)/8;

		for (j = nblocks_I; j < nblocks_H; j++)
		{
			store8(pk, mat[i][j]);
			pk += 8;
		}
	}

	//

	return 0;
}

