/* Portable C code to create DES key schedules from user-provided keys
 * This doesn't have to be fast unless you're cracking keys or UNIX
 * passwords
 */

#include <string.h>

/* Key schedule-related tables from FIPS-46 */

/* permuted choice table (key) */
static unsigned char pc1[] = {
	57, 49, 41, 33, 25, 17,  9,
	 1, 58, 50, 42, 34, 26, 18,
	10,  2, 59, 51, 43, 35, 27,
	19, 11,  3, 60, 52, 44, 36,

	63, 55, 47, 39, 31, 23, 15,
	 7, 62, 54, 46, 38, 30, 22,
	14,  6, 61, 53, 45, 37, 29,
	21, 13,  5, 28, 20, 12,  4
};

/* number left rotations of pc1 */
static unsigned char totrot[] = {
	1,2,4,6,8,10,12,14,15,17,19,21,23,25,27,28
};

/* permuted choice key (table) */
static unsigned char pc2[] = {
	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
};

/* End of DES-defined tables */


/* bit 0 is left-most in byte */
static int bytebit[] = {
	0200,0100,040,020,010,04,02,01
};


/* Generate key schedule for encryption or decryption
 * depending on the value of "decrypt"
 */
static void
deskey(k,key/*,decrypt*/)
unsigned long k[16][2];		/* Key schedule array */
const unsigned char *key;	/* 64 bits (will use only 56) */
/*int decrypt;*/		/* 0 = encrypt, 1 = decrypt */
{
	unsigned char pc1m[56];		/* place to modify pc1 into */
	unsigned char pcr[56];		/* place to rotate pc1 into */
	register int i,j,l;
	int m, n;
	unsigned char ks[8];

	for (j=0; j<56; j++) {		/* convert pc1 to bits of key */
		l=pc1[j]-1;		/* integer bit location	 */
		m = l & 07;		/* find bit		 */
		n = key[l >> 3] & bytebit[m];
		pc1m[j]=n ? 1 : 0;	/* find which key byte l is in */
					/* and which bit of that byte */
					/* and store 1-bit result */
	}
	for (i=0; i<16; i++) {		/* key chunk for each iteration */
		memset(ks,0,sizeof(ks));	/* Clear key schedule */
		for (j=0; j<56; j++) {	/* rotate pc1 the right amount */
			l=j+totrot[/*decrypt? 15-i :*/ i];
			pcr[j] = pc1m[l<(j<28? 28 : 56) ? l: l-28];
			/* rotate left and right halves independently */
		}
		for (j=0; j<48; j++){	/* select bits individually */
			/* check bit that goes to ks[j] */
			if (pcr[pc2[j]-1]){
				/* mask it in if it's there */
				l= j % 6;
				ks[j/6] |= bytebit[l] >> 2;
			}
		}
		/* Now convert to packed odd/even interleaved form */
		k[i][0] = ((long)ks[0] << 24)
		 | ((long)ks[2] << 16)
		 | ((long)ks[4] << 8)
		 | ((long)ks[6]);
		k[i][1] = ((long)ks[1] << 24)
		 | ((long)ks[3] << 16)
		 | ((long)ks[5] << 8)
		 | ((long)ks[7]);
	}
}