NAME    [Toc]    [Back]

     MD2Init, MD2Update, MD2Final, MD2End, MD2File, MD2Data - calculate the
     RSA Data Security, Inc., ``MD2'' message digest

LIBRARY    [Toc]    [Back]

     Standard C Library (libc, -lc)

SYNOPSIS    [Toc]    [Back]

     #include <sys/types.h>
     #include <md2.h>

     void
     MD2Init(MD2_CTX *context);

     void
     MD2Update(MD2_CTX *context, unsigned char *data, unsigned int len);

     void
     MD2Final(unsigned char digest[16], MD2_CTX *context);

     char *
     MD2End(MD2_CTX *context, char *buf);

     char *
     MD2File(char *filename, char *buf);

     char *
     MD2Data(unsigned char *data, unsigned int len, char *buf);

DESCRIPTION    [Toc]    [Back]

     The MD2 functions calculate a 128-bit cryptographic checksum (digest) for
     any number of input bytes.  A cryptographic checksum is a one-way hashfunction,
 that is, you cannot find (except by exhaustive search) the
     input corresponding to a particular output.  This net result is a ``fingerprint''
 of the input-data, which doesn't disclose the actual input.

     MD2 is the slowest, MD4 is the fastest and MD5 is somewhere in the middle.
  MD2 can only be used for Privacy-Enhanced Mail.  MD4 has been criticized
 for being too weak, so MD5 was developed in response as ``MD4 with
     safety-belts''.  When in doubt, use MD5.

     The MD2Init(), MD2Update(), and MD2Final() functions are the core functions.
  Allocate an MD2_CTX, initialize it with MD2Init(), run over the
     data with MD2Update(), and finally extract the result using MD2Final().

     MD2End() is a wrapper for MD2Final() which converts the return value to a
     33-character (including the terminating '\0') ASCII string which represents
 the 128 bits in hexadecimal.

     MD2File() calculates the digest of a file, and uses MD2End() to return
     the result.  If the file cannot be opened, a null pointer is returned.
     MD2Data() calculates the digest of a chunk of data in memory, and uses
     MD2End() to return the result.

     When using MD2End(), MD2File(), or MD2Data(), the buf argument can be a
     null pointer, in which case the returned string is allocated with
     malloc(3) and subsequently must be explicitly deallocated using free(3)
     after use.  If the buf argument is non-null it must point to at least 33
     characters of buffer space.

SEE ALSO    [Toc]    [Back]

     md2(3), md4(3), md5(3)

     B. Kaliski, The MD2 Message-Digest Algorithm, RFC 1319.

     R. Rivest, The MD4 Message-Digest Algorithm, RFC 1186.

     R. Rivest, The MD5 Message-Digest Algorithm, RFC 1321.

     RSA Laboratories, Frequently Asked Questions About today's Cryptography.

HISTORY    [Toc]    [Back]

     These functions appeared in NetBSD 1.3.

AUTHORS    [Toc]    [Back]

     The original MD2 routines were developed by RSA Data Security, Inc., and
     published in the above references.  This code is derived directly from
     these implementations by Poul-Henning Kamp <phk@login.dkuug.dk>

     Phk ristede runen.

BUGS    [Toc]    [Back]

     No method is known to exist which finds two files having the same hash
     value, nor to find a file with a specific hash value.  There is on the
     other hand no guarantee that such a method doesn't exist.

COPYRIGHT    [Toc]    [Back]

     This code is in the public domain.

BSD                             October 9, 1996                            BSD