MD2(3) BSD Library Functions Manual MD2(3)
MD2Init, MD2Update, MD2Final, MD2End, MD2File, MD2Data -- calculate the
RSA Data Security, Inc., ``MD2'' message digest
Standard C Library (libc, -lc)
MD2Update(MD2_CTX *context, const unsigned char *data, unsigned int len);
MD2Final(unsigned char digest, MD2_CTX *context);
MD2End(MD2_CTX *context, char *buf);
MD2File(const char *filename, char *buf);
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
input corresponding to a particular output. This net result is a ``fin-
gerprint'' 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 been crit-
icized 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 func-
tions. 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 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.
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.
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.
These functions appeared in NetBSD 1.3.
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 <phkATlogin.dk>
Phk ristede runen.
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.
This code is in the public domain.
BSD June 13, 2003 BSD