des.cpp

DES加密解密的算法

/* des: duplicate the NBS Data Encryption Standard in software.
 * usage: des <file>
 * prompts for the password
 * If the filename ends in ".n" it will be decrypted with the key;
 * otherwise it will be encrypted.
 *
 * Permutation algorithm:
 *	The permutation is defined by its effect on each of the 16 nibbles
 *	of the 64-bit input.  For each nibble we give an 8-byte bit array
 *	that has the bits in the input nibble distributed correctly.  The
 *	complete permutation involves ORing the 16 sets of 8 bytes designated
 *	by the 16 input nibbles.  Uses 16*16*8 = 2K bytes of storage for
 *	each 64-bit permutation.  32-bit permutations (P) and expansion (E)
 *	are done similarly, but using bytes instead of nibbles.
 *	Should be able to use long ints, adding the masks, at a
 *	later pass.  Tradeoff: can speed 64-bit perms up at cost of slowing 
 *	down expansion or contraction operations by using 8K tables here and
 *	decreasing the size of the other tables.
 * The compressions are pre-computed in 12-bit chunks, combining 2 of the
 *	6->4 bit compressions.
 * The key schedule is also precomputed.
 * Compile with VALIDATE defined to run the NBS validation suite.
 *
 * Jim Gillogly, May 1977
 * Modified 8/84 by Jim Gillogly and Lauren Weinstein to compile with
 *   post-1977 C compilers and systems
 *
 * This program is now officially in the public domain, and is available for
 * any non-profit use as long as the authorship line is retained.
 */

#include <stdio.h>
#include "des.h"

int getcomp(int k,int v);
void expand(char *right, char *bigright);
void contract(char *in48, char *out32);
void perm32(char *inblock, char *outblock);

char iperm[16][16][8],fperm[16][16][8]; /* inital and final permutations*/
char s[4][4096];			/* S1 thru S8 precomputed	*/
char p32[4][256][4];			/* for permuting 32-bit f output*/
char kn[16][6];				/* key selections		*/

void permute(char *inblock, char perm[16][16][8], char *outblock)		/* permute inblock with perm	*/
		/* result into outblock,64 bits */
			/* 2K bytes defining perm.	*/
{	register int i,j;
	register char *ib, *ob;		/* ptr to input or output block */
	register char *p, *q;

	for (i=0, ob = outblock; i<8; i++)
		*ob++ = 0;		/* clear output block		*/
	ib = inblock;
	for (j = 0; j < 16; j += 2, ib++) /* for each input nibble	*/
	{	ob = outblock;
		p = perm[j][(*ib >> 4) & 017];
		q = perm[j + 1][*ib & 017];
		for (i = 0; i < 8; i++)   /* and each output byte	*/
			*ob++ |= *p++ | *q++;   /* OR the masks together*/
	}
}

char ip[]				/* initial permutation P	*/
= {	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	};

char fp[]				/* final permutation F	  */
= {	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	};

/* expansion operation matrix   */	/* rwo: unused	*/
/* char ei[] = {	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  };	*/

char pc1[]				/* permuted choice table (key)  */
= {	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	};

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

char pc1m[56];			  /* place to modify pc1 into	*/
char pcr[56];			   /* place to rotate pc1 into	*/

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

char si[8][64]			  /* 48->32 bit compression tables*/
= {					/* S[1]			 */
	14,  4, 13,  1,  2, 15, 11,  8,  3, 10,  6, 12,  5,  9,  0,  7,
	 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,
					/* S[2]			 */
	15,  1,  8, 14,  6, 11,  3,  4,  9,  7,  2, 13, 12,  0,  5, 10,
	 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,
					/* S[3]			 */
	10,  0,  9, 14,  6,  3, 15,  5,  1, 13, 12,  7, 11,  4,  2,  8,
	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,
					/* S[4]			 */
	 7, 13, 14,  3,  0,  6,  9, 10,  1,  2,  8,  5, 11, 12,  4, 15,
	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,
					/* S[5]			 */
	 2, 12,  4,  1,  7, 10, 11,  6,  8,  5,  3, 15, 13,  0, 14,  9,
	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,
					/* S[6]			 */
	12,  1, 10, 15,  9,  2,  6,  8,  0, 13,  3,  4, 14,  7,  5, 11,
	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,
					/* S[7]			 */
	 4, 11,  2, 14, 15,  0,  8, 13,  3, 12,  9,  7,  5, 10,  6,  1,
	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,
					/* S[8]			 */
	13,  2,  8,  4,  6, 15, 11,  1, 10,  9,  3, 14,  5,  0, 12,  7,
	 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	};

char p32i[]				/* 32-bit permutation function  */
= {	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	};

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

int nibblebit[] = { 010,04,02,01 };

void sinit()				 /* initialize s1-s8 arrays		*/
{	register int i,j;

	for (i=0; i<4; i++)		/* each 12-bit position		*/
		for (j=0; j<4096; j++)  /* each possible 12-bit value   */
			s[i][j]=(getcomp(i*2,j>>6)<<4) |
				(017&getcomp(i*2+1,j&077));
					/* store 2 compressions per char*/
}

int getcomp(int k,int v)				/* 1 compression value for sinit*/
{	register int i,j;		/* correspond to i and j in FIPS*/

	i=((v&040)>>4)|(v&1);		/* first and last bits make row */
	j=(v&037)>>1;			/* middle 4 bits are column	*/
	return (int) si[k][(i<<4)+j];   /* result is ith row, jth col   */
}

void kinit(char *key)				/* initialize key schedule array*/
				/* 64 bits (will use only 56)   */
{	register int i,j,l;
	int m;

	for (j=0; j<56; j++)		/* convert pc1 to bits of key   */
	{	l=pc1[j]-1;		/* integer bit location		*/
		m = l & 07;		/* find bit			*/
		pc1m[j]=(key[l>>3] &	/* find which key byte l is in  */
			bytebit[m])	/* and which bit of that byte   */
			? 1 : 0;	/* and store 1-bit result	*/
	}

	for (i=0; i<16; i++)		/* for each key sched section   */
		for (j=0; j<6; j++)	/* and each byte of the kn	*/
			kn[i][j]=0;	/* clear it for accumulation	*/
	for (i=0; i<16; i++)		/* key chunk for each iteration */
	{	for (j=0; j<56; j++)	/* rotate pc1 the right amount  */
			pcr[j] = pc1m[(l=j+totrot[i])<(j<28? 28 : 56) ? l: l-28];
				/* rotate left and right halves independently   */
		for (j=0; j<48; j++)	/* select bits individually	*/
			if (pcr[pc2[j]-1])	/* check bit that goes to kn[j] */
				{	l= j & 07;
					kn[i][j>>3] |= bytebit[l];
				}		/* mask it in if it's there	*/
	}