md2c.c

算法源代码比较经典

/* Modifications Copyright (c) J.S.A.Kapp 1994 - 1995.

	 MD2 Component Of RSAEURO using RSA Data Security, Inc.
	 MD2 Message Digest Algorithm.

	 All Trademarks Acknowledged.

	 Future versions may not use this modified RSADSI implementation
	 of MD2.
*/

/* Copyright (C) 1990-2, RSA Data Security, Inc. Created 1990. All
	 rights reserved.

	 License to copy and use this software is granted for
	 non-commercial Internet Privacy-Enhanced Mail provided that it is
	 identified as the "RSA Data Security, Inc. MD2 Message Digest
	 Algorithm" in all material mentioning or referencing this software
	 or this function.

	 RSA Data Security, Inc. makes no representations concerning either
	 the merchantability of this software or the suitability of this
	 software for any particular purpose. It is provided "as is"
	 without express or implied warranty of any kind.

	 These notices must be retained in any copies of any part of this
	 documentation and/or software.
*/

#include "rsaeuro.h"
#include "md2.h"

static void MD2Transform PROTO_LIST
	((unsigned char [16], unsigned char [16], unsigned char [16]));

/* Permutation of 0..255 constructed from the digits of pi. It gives a
	 "random" nonlinear byte substitution operation.
*/
static unsigned char PI_SUBST[256] = {
  41, 46, 67, 201, 162, 216, 124, 1, 61, 54, 84, 161, 236, 240, 6,
  19, 98, 167, 5, 243, 192, 199, 115, 140, 152, 147, 43, 217, 188,
  76, 130, 202, 30, 155, 87, 60, 253, 212, 224, 22, 103, 66, 111, 24,
  138, 23, 229, 18, 190, 78, 196, 214, 218, 158, 222, 73, 160, 251,
	245, 142, 187, 47, 238, 122, 169, 104, 121, 145, 21, 178, 7, 63,
  148, 194, 16, 137, 11, 34, 95, 33, 128, 127, 93, 154, 90, 144, 50,
  39, 53, 62, 204, 231, 191, 247, 151, 3, 255, 25, 48, 179, 72, 165,
	181, 209, 215, 94, 146, 42, 172, 86, 170, 198, 79, 184, 56, 210,
  150, 164, 125, 182, 118, 252, 107, 226, 156, 116, 4, 241, 69, 157,
  112, 89, 100, 113, 135, 32, 134, 91, 207, 101, 230, 45, 168, 2, 27,
  96, 37, 173, 174, 176, 185, 246, 28, 70, 97, 105, 52, 64, 126, 15,
  85, 71, 163, 35, 221, 81, 175, 58, 195, 92, 249, 206, 186, 197,
  234, 38, 44, 83, 13, 110, 133, 40, 132, 9, 211, 223, 205, 244, 65,
  129, 77, 82, 106, 220, 55, 200, 108, 193, 171, 250, 36, 225, 123,
  8, 12, 189, 177, 74, 120, 136, 149, 139, 227, 99, 232, 109, 233,
  203, 213, 254, 59, 0, 29, 57, 242, 239, 183, 14, 102, 88, 208, 228,
  166, 119, 114, 248, 235, 117, 75, 10, 49, 68, 80, 180, 143, 237,
  31, 26, 219, 153, 141, 51, 159, 17, 131, 20
};

static unsigned char *PADDING[] = {
  (unsigned char *)"",
  (unsigned char *)"\001",
  (unsigned char *)"\002\002",
  (unsigned char *)"\003\003\003",
  (unsigned char *)"\004\004\004\004",
  (unsigned char *)"\005\005\005\005\005",
  (unsigned char *)"\006\006\006\006\006\006", 
  (unsigned char *)"\007\007\007\007\007\007\007",
  (unsigned char *)"\010\010\010\010\010\010\010\010",
  (unsigned char *)"\011\011\011\011\011\011\011\011\011",
  (unsigned char *)"\012\012\012\012\012\012\012\012\012\012",
  (unsigned char *)"\013\013\013\013\013\013\013\013\013\013\013",
  (unsigned char *)"\014\014\014\014\014\014\014\014\014\014\014\014",
  (unsigned char *)
		"\015\015\015\015\015\015\015\015\015\015\015\015\015",
  (unsigned char *)
    "\016\016\016\016\016\016\016\016\016\016\016\016\016\016",
  (unsigned char *)
		"\017\017\017\017\017\017\017\017\017\017\017\017\017\017\017",
	(unsigned char *)
		"\020\020\020\020\020\020\020\020\020\020\020\020\020\020\020\020"
};

/* MD2 initialization. Begins an MD2 operation, writing a new context. */

void MD2Init(context)
MD2_CTX *context;               /* context */
{
	context->count = 0;
	R_memset((POINTER)context->state, 0, sizeof(context->state));
	R_memset((POINTER)context->checksum, 0, sizeof(context->checksum));
}

/* MD2 block update operation. Continues an MD2 message-digest
	 operation, processing another message block, and updating the
	 context.
*/

void MD2Update(context, input, inputLen)
MD2_CTX *context;               /* context */
unsigned char *input;           /* input block */
unsigned int inputLen;          /* length of input block */
{
	unsigned int i, index, partLen;

	/* Update number of bytes mod 16 */
	index = context->count;
	context->count = (index + inputLen) & 0xf;

	partLen = 16 - index;

	/* Transform as many times as possible.	*/

	if(inputLen >= partLen) {
		R_memcpy((POINTER)&context->buffer[index], (POINTER)input, partLen);
		MD2Transform(context->state, context->checksum, context->buffer);

		for(i = partLen; i + 15 < inputLen; i += 16)
			MD2Transform(context->state, context->checksum, &input[i]);

		index = 0;
	}
	else
		i = 0;

	/* Buffer remaining input */

	R_memcpy((POINTER)&context->buffer[index], (POINTER)&input[i], inputLen-i);
}

/* MD2 finalization. Ends an MD2 message-digest operation, writing the
	 message digest and zeroizing the context. */

void MD2Final(digest, context)
unsigned char digest[16];                         /* message digest */
MD2_CTX *context;                                        /* context */
{
	unsigned int index, padLen;

	/* Pad out to multiple of 16. */

	index = context->count;
	padLen = 16 - index;
	MD2Update(context, PADDING[padLen], padLen);

	/* Extend with checksum */

	MD2Update(context, context->checksum, 16);

	/* Store state in digest */

	R_memcpy((POINTER)digest, (POINTER)context->state, 16);

	/* Zeroize sensitive information. */

	R_memset((POINTER)context, 0, sizeof(*context));
}

/* MD2 basic transformation. Transforms state and updates checksum
	 based on block. */

static void MD2Transform(state, checksum, block)
unsigned char state[16];
unsigned char checksum[16];
unsigned char block[16];
{
	unsigned int i, j, t;
	unsigned char x[48];

	/* Form encryption block from state, block, state ^ block. */

	R_memcpy((POINTER)x, (POINTER)state, 16);
	R_memcpy((POINTER)x+16, (POINTER)block, 16);
	for(i = 0; i < 16; i++)
    x[i+32] = state[i] ^ block[i];
  
  /* Encrypt block (18 rounds).
   */
  t = 0;
  for (i = 0; i < 18; i++) {
    for (j = 0; j < 48; j++)
      t = x[j] ^= PI_SUBST[t];
    t = (t + i) & 0xff;
  }
    
  /* Save new state */
	R_memcpy((POINTER)state, (POINTER)x, 16);

	/* Update checksum. */

	t = checksum[15];
	for(i = 0; i < 16; i++)
		t = checksum[i] ^= PI_SUBST[block[i] ^ t];

	/* Zeroize sensitive information. */

	R_memset((POINTER)x, 0, sizeof(x));
}