FreeBSD Manual Pages
MD2(3) BSD Library Functions Manual MD2(3) NAME MD2Init, MD2Update, MD2Pad, MD2Final, MD2End, MD2File, MD2FileChunk, MD2Data -- calculate the RSA Data Security, Inc., ``MD2'' message digest LIBRARY Message Digest (MD4, MD5, etc.) Support Library (libmd, -lmd) SYNOPSIS #include <sys/types.h> #include <md2.h> void MD2Init(MD2_CTX *context); void MD2Update(MD2_CTX *context, const unsigned char *data, unsigned int len); void MD2Pad(MD2_CTX *context); void 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); DESCRIPTION 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 value. 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- sult. 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 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, <http://www.rsa.com/rsalabs/faq/>. 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. AUTHORS 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@FreeBSD.org> Phk ristede runen. HISTORY These functions appeared in FreeBSD 2.0. BUGS 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
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | SEE ALSO | AUTHORS | HISTORY | BUGS
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=md2&sektion=3&manpath=FreeBSD+5.0-RELEASE>