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MD2(3)			 BSD Library Functions Manual			MD2(3)

     MD2Init, MD2Update, MD2Pad, MD2Final, MD2End, MD2File, MD2FileChunk,
     MD2Data --	calculate the RSA Data Security, Inc., ``MD2'' message digest

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

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

     MD2Init(MD2_CTX *context);

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

     MD2Pad(MD2_CTX *context);

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

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

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

     char *
     MD2FileChunk(const	char *filename,	char *buf, off_t offset,
	 off_t length);

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

     The MD2 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 in-
     put corresponding to a particular output.	This net result	is a ``finger-
     print'' 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	mid-
     dle.  MD2 can only	be used	for Privacy-Enhanced Mail.  MD4	has now	been
     broken; it	should only be used where necessary for	backward compatibil-
     ity.  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

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

     MD2Pad() can be used to pad message data in same way as done by
     MD2Final()	without	terminating calculation.

     MD2End() is a wrapper for MD2Final() which	converts the return value to a
     33-character (including the terminating '\0') ASCII string	which repre-
     sents 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.
     MD2FileChunk() is similar to MD2File(), 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, MD2FileChunk() calculates
     the digest	from offset to the end of file.	 MD2Data() calculates the di-
     gest of a chunk of	data in	memory,	and uses MD2End() to return the	re-

     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.

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

     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.

     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 ristede runen.

     These functions appeared in FreeBSD 2.0.

     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.

     MD2 has only been licensed	for use	in Privacy Enhanced Mail.  Use MD4 or
     MD5 if that isn't what you're doing.  Copyright (C) 1990-2, RSA Data Se-
     curity, Inc. Created 1990.	All rights reserved.

     License to	copy and use this software is granted for non-commercial In-
     ternet Privacy-Enhanced Mail provided that	it is identified as the	"RSA
     Data Security, Inc. MD2 Message Digest Algorithm" in all material men-
     tioning 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 documen-
     tation and/or software.

BSD			       February	11, 1999			   BSD


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