#include <stdio.h>

static int keyout[17][48];

void des_init(),lshift(),cypher(),des_encrypt(),des_descrypt();

void des_init(unsigned char *key){
 unsigned char c[28],d[28];
 static int pc1[56] = {57,49,41,33,25,17,9,
		      01,58,50,42,34,26,18,
		      10,02,59,51,43,35,27,
		      19,11,03,60,52,44,36,
		      63,55,47,39,31,23,15,
		      07,62,54,46,38,30,22,
		      14,06,61,53,45,37,29,
		      21,13,05,28,20,12,04};
 static int pc2[48] = {14,17,11,24,1,5,
		      3,28,15,6,21,10,
		      23,19,12,4,26,8,
		      16,7,27,20,13,2,
		      41,52,31,37,47,55,
		      30,40,51,45,33,48,
		      44,49,39,56,34,53,
		      46,42,50,36,29,32};
 static int nls[17] = {
  0,1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1};

 static int cd[56],keyb[64];
 static int cnt,n=0;
 register int i,j;

 for(i=0;i<8;i++) /*Read in key*/
  for(j=0;j<8;j++) keyb[n++]=(key[i]>>j&0x01);

 for(i=0;i<56;i++) /*Permuted choice 1*/
  cd[i]=keyb[pc1[1]-1];
 for(i=0;i<28;i++){
  c[i]=cd[i];
  d[i]=cd[i+28];
 }
 for(cnt=1;cnt<=16;cnt++){
  for(i=0;i<nls[cnt];i++){
   lshift(c); lshift(d);
  }
  for(i=0;i<28;i++){
   cd[i]=c[i];
   cd[i+28]=d[i];
  }
  for(i=0;i<48;i++) /*Permuted Choice 2*/
   keyout[cnt][i]=cd[pc2[i]-1];
 }
}

static void lshift(unsigned char shft[]){
 register int temp,i;

 temp=shft[0];
 for(i=0;i<27;i++) shft[i]=shft[i+1];
 shft[27]=temp;
}

static void cypher(int *r, int cnt, int *fout){
 static int expand[48],b[8][6],sout[8],pin[48];
 register int i,j;
 static int n,row,col,scnt;
 static int p[32]={
	16,7,20,21,29,12,28,17,1,15,23,26,
	 5,18,31,10,2,8,24,14,32,27,3,9,
	19,13,30,6,22,11,4,25};

 static int   e[48] = {32,1,2,3,4,5,
		      4,5,6,7,8,9,
		      8,9,10,11,12,13,
		      12,13,14,15,16,17,
		      16,17,18,19,20,21,
		      20,21,22,23,24,25,
		      24,25,26,27,28,29,
		      28,29,30,31,32,1};

 static char s[8][64] = {
	14,4,13,1,2,15,11,8,3,10,6,12,5,9,0,7, /*s1*/
	 0,15,7,4,14,2,13,1,10,6,12,11,9,5,3,8,
	 4,1,14,8,13,6,2,11,15,12,9,7,3,10,5,0,
	15,12,8,2,4,9,1,7,5,11,3,14,10,0,6,13,
	15,1,8,14,6,11,3,4,9,7,2,13,12,0,5,10, /*s2*/
	 3,13,4,7,15,2,8,14,12,0,1,10,6,9,11,5,
	 0,14,7,11,10,4,13,1,5,8,12,6,9,3,2,15,
	13,8,10,1,3,15,4,2,11,6,7,12,0,5,14,9,
	10,0,9,14,6,3,15,5,1,13,12,7,11,4,2,8, /*s3*/
	13,7,0,9,3,4,6,10,2,8,5,14,12,11,15,1,
	13,6,4,9,8,15,3,0,11,1,2,12,5,10,14,7,
	 1,10,13,0,6,9,8,7,4,15,14,3,11,5,2,12,
	 7,13,14,3,0,6,9,10,1,2,8,5,11,12,4,15,/*s4*/
	13,8,11,5,6,15,0,3,4,7,2,12,1,10,14,9,
	10,6,9,0,12,11,7,13,15,1,3,14,5,2,8,4,
	 3,15,0,6,10,1,13,8,9,4,5,11,12,7,2,14,
	 2,12,4,1,7,10,11,6,8,5,3,15,13,0,14,9,/*s5*/
	14,11,2,12,4,7,13,1,5,0,15,10,3,9,8,6,
	 4,2,1,11,10,13,7,8,15,9,12,5,6,3,0,14,
	11,8,12,7,1,14,2,13,6,15,0,9,10,4,5,3,
	12,1,10,15,9,2,6,8,0,13,3,4,14,7,5,11, /*s6*/
	10,15,4,2,7,12,9,5,6,1,13,14,0,11,3,8,
	 9,14,15,5,2,8,12,3,7,0,4,10,1,13,11,6,
	 4,3,2,12,9,5,15,10,11,14,1,7,6,0,8,13,
	 4,11,2,14,15,0,8,13,3,12,9,7,5,10,6,1,/*s7*/
	13,0,11,7,4,9,1,10,14,3,5,12,2,15,8,6,
	 1,4,11,13,12,3,7,14,10,15,6,8,0,5,9,2,
	 6,11,13,8,1,4,10,7,9,5,0,15,14,2,3,12,
	13,2,8,4,6,15,11,1,10,9,3,14,5,0,12,7, /*s8*/
	 1,15,13,8,10,3,7,4,12,5,6,11,0,14,9,2,
	 7,11,4,1,9,12,14,2,0,6,10,13,15,3,5,8,
	 2,1,14,7,4,10,8,13,15,12,9,0,3,5,6,11
 };

 for(i=0;i<48;i++) expand[i]=r[e[i]-1]; /*Expansion Function*/
 for(i=n=0;i<8;i++) {
  for(j=0;j<6;j++,n++) b[i][j]=expand[n]^keyout[cnt][n];
 }

 /*Selection functions*/

  for(scnt=n=0;scnt<8;scnt++){
   row=(b[scnt][0]<<1)+b[scnt][5];
   col=(b[scnt][1]<<3)+(b[scnt][2]<<2)+(b[scnt][3]<<1)+b[scnt][4];
   sout[scnt]=s[scnt][(row<<4)+col];
   for(i=3;i>=0;i--){
    pin[n]=sout[scnt]>>i;
    sout[scnt]=sout[scnt]-(pin[n++]<<i);
   }
  }
  for(i=0;i<32;i++) fout[i]=pin[p[i]-1]; /*Permutation Function*/
}

static int p[64] = {58,50,42,34,26,18,10,2,
		      60,52,44,36,28,20,12,4,
		      62,54,46,38,30,22,14,6,
		      64,56,48,40,32,24,16,8,
		      57,49,41,33,25,17,9,1,
		      59,51,43,35,27,19,11,3,
		      61,53,45,37,29,21,13,5,
		      63,55,47,39,31,23,15,7};

static int invp[64]={
 40, 8,48,16,56,24,64,32,39, 7,47,15,55,23,63,31,
 38, 6,46,14,54,22,62,30,37, 5,45,13,53,21,61,29,
 36, 4,44,12,52,20,60,28,35, 3,43,11,51,19,59,27,
 34, 2,42,10,50,18,58,26,33, 1,41, 9,49,17,57,25};

void des_encrypt(unsigned char *input){
 static unsigned char out[64];
 static int inputb[64],lr[64],l[32],r[32];
 static int fn[32];
 static int cnt,n;
 register int i,j;

 for(i=n=0;i<8;i++)
  for(j=0;j<8;j++) inputb[n++]=(input[i]>>j&0x01);

 for(i=0;i<64;i++){ /*Initial Permutation*/
  lr[i]=inputb[p[i]-1];
  if(i<32) l[i]=lr[i];
  else r[i-32]=lr[i];
 }
 for(cnt=1;cnt<=16;cnt++){ /*Main encryption loop*/
  cypher(r,cnt,fn);
  for(i=0;i<32;i++){
   j=r[i];
   r[i]=l[i]^fn[i];
   l[i]=j;
  }
 }
 for(i=0;i<32;i++){
  lr[i]=r[i];
  lr[i+32]=l[i];
 }
 for(i=0;i<64;i++) out[i]=lr[invp[i]-1]; /*Inverse IP*/

 for(i=1;i<=8;i++)
  for(j=1;j<=8;j++) input[i-1]=(input[i-1]<<1)|out[i*8-j];
}

void des_decrypt(unsigned char *input){
 static unsigned char out[64];
 static int inputb[64],lr[64],l[32],r[32];
 static int fn[32];
 static int cnt,rtemp,n;
 register int i,j;

 for(i=n=0;i<8;i++)
  for(j=0;j<8;j++) inputb[n++]=(input[i]>>j&0x01);

 for(i=0;i<64;i++){ /*Initial Permutation*/
  lr[i]=inputb[p[i]-1];
  if(i<32) l[i]=lr[i];
  else r[i-32]=lr[i];
 }
 for(cnt=16;cnt>0;cnt--){ /*Main decryption loop*/
  cypher(r,cnt,fn);
  for(i=0;i<32;i++){
   rtemp=r[i];
   if(l[i]==1 && fn[i]==1) r[i]=0;
   else r[i]=(l[i] || fn[i]);
   l[i]=rtemp;
  }
 }
 for(i=0;i<32;i++){
  lr[i]=r[i];
  lr[i+32]=l[i];
 }
 for(i=0;i<64;i++) out[i]=lr[invp[i]-1]; /*Inverse IP*/

 for(i=1;i<=8;i++)
  for(j=1;j<=8;j++) input[i-1]=(input[i-1]<<1) | out[i*8-j];
}

int main(int argc, char *argv[]){
 unsigned char *key;
 unsigned char data[8];
 int n;
 FILE *in;
 FILE *out;

 if (argc!=4) {
  printf("\r\nUsage:  des [e][d] <source file> <destination file>\r\n");
  return 1;
 }

 key=(unsigned char*)getpass("Enter Key:");
 des_init(key);

 if((in=fopen(argv[2],"rb"))==NULL){
  fprintf(stderr,"\r\nCould not open input file: %s",argv[2]);
  return 2;
 }

 if((out=fopen(argv[3],"wb"))==NULL){
  fprintf(stderr,"\r\nCould not open output file: %s",argv[3]);
  return 3;
 }

 if(argv[1][0]=='e'){
  while ((n=fread(data,1,8,in)) >0){
   des_encrypt(data);
   printf("data enctyted");
   if(fwrite(data,1,8,out) < 8){
    fprintf(stderr,"\r\nError writing to output file\r\n");
    return(3);
   }
  }
 }

 if(argv[1][0]=='d'){
  while ((n=fread(data,1,8,in)) >0){
   des_decrypt(data);
   if(fwrite(data,1,8,out) < 8){
    fprintf(stderr,"\r\nError writing to output file\r\n");
    return(3);
   }
  }
 }

 fclose(in); fclose(out);
 return 0;
}