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/*
* $Id: gost.c,v 1.2 2003/04/27 20:54:42 andrew_belov Exp $
* ---------------------------------------------------------------------------
* This file contains basic GOST encryption-related initialization data and
* code.
*
*/
#include "arj.h"
DEBUGHDR(__FILE__) /* Debug information block */
/* Makes a 1024-byte pattern for encryption */
void calc_gost_pattern()
{
int i;
for(i=0; i<256; i++)
{
pattern[0][i]=(seed[0][i>>4]<<4)|(seed[1][i&0x0F]);
pattern[1][i]=(seed[2][i>>4]<<4)|(seed[3][i&0x0F]);
pattern[2][i]=(seed[4][i>>4]<<4)|(seed[5][i&0x0F]);
pattern[3][i]=(seed[6][i>>4]<<4)|(seed[7][i&0x0F]);
}
}
/* Basic step of GOST encoding */
#ifdef WORDS_BIGENDIAN
#define _dptr(i) (dptr[3-(i)])
#else
#define _dptr(i) (dptr[ (i)])
#endif
unsigned long gost_term(unsigned long data)
{
unsigned char *dptr;
unsigned short p1, p2;
unsigned short hi, lo;
dptr=(unsigned char *)&data;
p1=(pattern[0][_dptr(3)]<<8)+pattern[1][_dptr(2)];
p2=(pattern[2][_dptr(1)]<<8)+pattern[3][_dptr(0)];
hi=(p1<<GSH_BITS)|(p2>>(16-GSH_BITS));
lo=(p2<<GSH_BITS)|(p1>>(16-GSH_BITS));
return(((unsigned long)hi<<16)+(unsigned long)lo);
}
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