RFC 1321              MD5 Message-Digest Algorithm            April 1992*/  MD5_memset ((POINTER)x, 0, sizeof (x));}/* Encodes input (UINT4) into output (unsigned char). Assumes len is  a multiple of 4. */static void Encode (output, input, len)unsigned char *output;UINT4 *input;unsigned int len;{  unsigned int i, j;  for (i = 0, j = 0; j < len; i++, j += 4) { output[j] = (unsigned char)(input[i] & 0xff); output[j+1] = (unsigned char)((input[i] >> 8) & 0xff); output[j+2] = (unsigned char)((input[i] >> 16) & 0xff); output[j+3] = (unsigned char)((input[i] >> 24) & 0xff);  }}/* Decodes input (unsigned char) into output (UINT4). Assumes len is  a multiple of 4. */static void Decode (output, input, len)UINT4 *output;unsigned char *input;unsigned int len;{  unsigned int i, j;  for (i = 0, j = 0; j < len; i++, j += 4) output[i] = ((UINT4)input[j]) | (((UINT4)input[j+1]) << 8) |   (((UINT4)input[j+2]) << 16) | (((UINT4)input[j+3]) << 24);}/* Note: Replace "for loop" with standard memcpy if possible. */static void MD5_memcpy (output, input, len)POINTER output;POINTER input;unsigned int len;{  unsigned int i;  for (i = 0; i < len; i++)Rivest                                                         [Page 15]RFC 1321              MD5 Message-Digest Algorithm            April 1992 output[i] = input[i];}/* Note: Replace "for loop" with standard memset if possible. */static void MD5_memset (output, value, len)POINTER output;int value;unsigned int len;{  unsigned int i;  for (i = 0; i < len; i++) ((char *)output)[i] = (char)value;}A.4 mddriver.c/* MDDRIVER.C - test driver for MD2, MD4 and MD5 *//* Copyright (C) 1990-2, RSA Data Security, Inc. Created 1990. Allrights reserved.RSA Data Security, Inc. makes no representations concerning eitherthe merchantability of this software or the suitability of thissoftware 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 thisdocumentation and/or software. *//* The following makes MD default to MD5 if it has not already been  defined with C compiler flags. */#ifndef MD#define MD MD5#endif#include <stdio.h>#include <time.h>#include <string.h>#include "global.h"#if MD == 2#include "md2.h"#endif#if MD == 4Rivest                                                         [Page 16]RFC 1321              MD5 Message-Digest Algorithm            April 1992#include "md4.h"#endif#if MD == 5#include "md5.h"#endif/* Length of test block, number of test blocks. */#define TEST_BLOCK_LEN 1000#define TEST_BLOCK_COUNT 1000static void MDString PROTO_LIST ((char *));static void MDTimeTrial PROTO_LIST ((void));static void MDTestSuite PROTO_LIST ((void));static void MDFile PROTO_LIST ((char *));static void MDFilter PROTO_LIST ((void));static void MDPrint PROTO_LIST ((unsigned char [16]));#if MD == 2#define MD_CTX MD2_CTX#define MDInit MD2Init#define MDUpdate MD2Update#define MDFinal MD2Final#endif#if MD == 4#define MD_CTX MD4_CTX#define MDInit MD4Init#define MDUpdate MD4Update#define MDFinal MD4Final#endif#if MD == 5#define MD_CTX MD5_CTX#define MDInit MD5Init#define MDUpdate MD5Update#define MDFinal MD5Final#endif/* Main driver.Arguments (may be any combination):  -sstring - digests string  -t       - runs time trial  -x       - runs test script  filename - digests file  (none)   - digests standard input */int main (argc, argv)int argc;Rivest                                                         [Page 17]RFC 1321              MD5 Message-Digest Algorithm            April 1992char *argv[];{  int i;  if (argc > 1) for (i = 1; i < argc; i++)   if (argv[i][0] == '-' && argv[i][1] == 's')     MDString (argv[i] + 2);   else if (strcmp (argv[i], "-t") == 0)     MDTimeTrial ();   else if (strcmp (argv[i], "-x") == 0)     MDTestSuite ();   else     MDFile (argv[i]);  else MDFilter ();  return (0);}/* Digests a string and prints the result. */static void MDString (string)char *string;{  MD_CTX context;  unsigned char digest[16];  unsigned int len = strlen (string);  MDInit (&context);  MDUpdate (&context, string, len);  MDFinal (digest, &context);  printf ("MD%d (\"%s\") = ", MD, string);  MDPrint (digest);  printf ("\n");}/* Measures the time to digest TEST_BLOCK_COUNT TEST_BLOCK_LEN-byte  blocks. */static void MDTimeTrial (){  MD_CTX context;  time_t endTime, startTime;  unsigned char block[TEST_BLOCK_LEN], digest[16];  unsigned int i;Rivest                                                         [Page 18]RFC 1321              MD5 Message-Digest Algorithm            April 1992  printf ("MD%d time trial. Digesting %d %d-byte blocks ...", MD,  TEST_BLOCK_LEN, TEST_BLOCK_COUNT);  /* Initialize block */  for (i = 0; i < TEST_BLOCK_LEN; i++) block[i] = (unsigned char)(i & 0xff);  /* Start timer */  time (&startTime);  /* Digest blocks */  MDInit (&context);  for (i = 0; i < TEST_BLOCK_COUNT; i++) MDUpdate (&context, block, TEST_BLOCK_LEN);  MDFinal (digest, &context);  /* Stop timer */  time (&endTime);  printf (" done\n");  printf ("Digest = ");  MDPrint (digest);  printf ("\nTime = %ld seconds\n", (long)(endTime-startTime));  printf ("Speed = %ld bytes/second\n",  (long)TEST_BLOCK_LEN * (long)TEST_BLOCK_COUNT/(endTime-startTime));}/* Digests a reference suite of strings and prints the results. */static void MDTestSuite (){  printf ("MD%d test suite:\n", MD);  MDString ("");  MDString ("a");  MDString ("abc");  MDString ("message digest");  MDString ("abcdefghijklmnopqrstuvwxyz");  MDString ("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789");  MDString ("1234567890123456789012345678901234567890\1234567890123456789012345678901234567890");}/* Digests a file and prints the result.Rivest                                                         [Page 19]RFC 1321              MD5 Message-Digest Algorithm            April 1992 */static void MDFile (filename)char *filename;{  FILE *file;  MD_CTX context;  int len;  unsigned char buffer[1024], digest[16];  if ((file = fopen (filename, "rb")) == NULL) printf ("%s can't be opened\n", filename);  else { MDInit (&context); while (len = fread (buffer, 1, 1024, file))   MDUpdate (&context, buffer, len); MDFinal (digest, &context); fclose (file); printf ("MD%d (%s) = ", MD, filename); MDPrint (digest); printf ("\n");  }}/* Digests the standard input and prints the result. */static void MDFilter (){  MD_CTX context;  int len;  unsigned char buffer[16], digest[16];  MDInit (&context);  while (len = fread (buffer, 1, 16, stdin)) MDUpdate (&context, buffer, len);  MDFinal (digest, &context);  MDPrint (digest);  printf ("\n");}/* Prints a message digest in hexadecimal. */static void MDPrint (digest)unsigned char digest[16];{Rivest                                                         [Page 20]RFC 1321              MD5 Message-Digest Algorithm            April 1992  unsigned int i;  for (i = 0; i < 16; i++) printf ("%02x", digest[i]);}A.5 Test suite   The MD5 test suite (driver option "-x") should print the following   results:MD5 test suite:MD5 ("") = d41d8cd98f00b204e9800998ecf8427eMD5 ("a") = 0cc175b9c0f1b6a831c399e269772661MD5 ("abc") = 900150983cd24fb0d6963f7d28e17f72MD5 ("message digest") = f96b697d7cb7938d525a2f31aaf161d0MD5 ("abcdefghijklmnopqrstuvwxyz") = c3fcd3d76192e4007dfb496cca67e13bMD5 ("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789") =d174ab98d277d9f5a5611c2c9f419d9fMD5 ("12345678901234567890123456789012345678901234567890123456789012345678901234567890") = 57edf4a22be3c955ac49da2e2107b67aSecurity Considerations   The level of security discussed in this memo is considered to be   sufficient for implementing very high security hybrid digital-   signature schemes based on MD5 and a public-key cryptosystem.Author's Address   Ronald L. Rivest   Massachusetts Institute of Technology   Laboratory for Computer Science   NE43-324   545 Technology Square   Cambridge, MA  02139-1986   Phone: (617) 253-5880   EMail: rivest@theory.lcs.mit.eduRivest                                                         [Page 21]