MD4(3)                 FreeBSD Library Functions Manual                 MD4(3)

NAME
     MD4Init, MD4Update, MD4Pad, MD4Final, MD4End, MD4File, MD4FileChunk,
     MD4Data - calculate the RSA Data Security, Inc., ``MD4'' message digest

LIBRARY
     Message Digest (MD4, MD5, etc.) Support Library (libmd, -lmd)

SYNOPSIS
     #include <sys/types.h>
     #include <md4.h>

     void
     MD4Init(MD4_CTX *context);

     void
     MD4Update(MD4_CTX *context, const void *data, unsigned int len);

     void
     MD4Pad(MD4_CTX *context);

     void
     MD4Final(unsigned char digest[16], MD4_CTX *context);

     char *
     MD4End(MD4_CTX *context, char *buf);

     char *
     MD4File(const char *filename, char *buf);

     char *
     MD4FileChunk(const char *filename, char *buf, off_t offset,
         off_t length);

     char *
     MD4Data(const void *data, unsigned int len, char *buf);

DESCRIPTION
     The MD4 functions calculate a 128-bit cryptographic checksum (digest) for
     any number of input bytes.  A cryptographic checksum is a one-way hash-
     function, 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 does not disclose the actual
     input.

     MD4 is the fastest and MD5 is somewhat slower.  MD4 has now been broken;
     it should only be used where necessary for backward compatibility.  MD5
     has not yet (1999-02-11) been broken, but sufficient attacks have been
     made that its security is in some doubt.  The attacks on both MD4 and MD5
     are both in the nature of finding "collisions" - that is, multiple inputs
     which hash to the same value; it is still unlikely for an attacker to be
     able to determine the exact original input given a hash value.

     The MD4Init(), MD4Update(), and MD4Final() functions are the core
     functions.  Allocate an MD4_CTX, initialize it with MD4Init(), run over
     the data with MD4Update(), and finally extract the result using
     MD4Final(), which will also erase the MD4_CTX.

     The MD4Pad() function can be used to pad message data in same way as done
     by MD4Final() without terminating calculation.

     The MD4End() function is a wrapper for MD4Final() which converts the
     return value to a 33-character (including the terminating '\0') ASCII
     string which represents the 128 bits in hexadecimal.

     The MD4File() function calculates the digest of a file, and uses MD4End()
     to return the result.  If the file cannot be opened, a null pointer is
     returned.  The MD4FileChunk() function is similar to MD4File(), but it
     only calculates the digest over a byte-range of the file specified,
     starting at offset and spanning length bytes.  If the length parameter is
     specified as 0, or more than the length of the remaining part of the
     file, MD4FileChunk() calculates the digest from offset to the end of
     file.  The MD4Data() function calculates the digest of a chunk of data in
     memory, and uses MD4End() to return the result.

     When using MD4End(), MD4File(), or MD4Data(), 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.

ERRORS
     The MD4End() function called with a null buf argument may fail and return
     NULL if:

     [ENOMEM]           Insufficient storage space is available.

     The MD4File() and MD4FileChunk() may return NULL when underlying open(2),
     fstat(2), lseek(2), or MD4End(2) fail.

SEE ALSO
     md4(3), md5(3), ripemd(3), sha(3), sha256(3), sha512(3), skein(3)

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

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

     H. Dobbertin, "Alf Swindles Ann", CryptoBytes, 1(3):5, 1995.

     MJ. B. Robshaw, "On Recent Results for MD2, MD4 and MD5", RSA
     Laboratories Bulletin, 4, November 12, 1996.

HISTORY
     These functions appeared in FreeBSD 2.0.

AUTHORS
     The original MD4 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@FreeBSD.org>.

     Phk ristede runen.

BUGS
     The MD5 algorithm has been proven to be vulnerable to practical collision
     attacks and should not be relied upon to produce unique outputs, nor
     should they be used as part of a cryptographic signature scheme.
     Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All rights
     reserved.

     License to copy and use this software is granted provided that it is
     identified as the "RSA Data Security, Inc. MD4 Message-Digest Algorithm"
     in all material mentioning or referencing this software or this function.
     License is also granted to make and use derivative works provided that
     such works are identified as "derived from the RSA Data Security, Inc.
     MD4 Message-Digest Algorithm" in all material mentioning or referencing
     the derived work.

     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.

FreeBSD 13.1-RELEASE-p6          May 21, 2019          FreeBSD 13.1-RELEASE-p6