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 ``fingerprint'' of the input-data, which doesn't disclose the actual input.
The MD2 routines should not be used for any security-related purpose.
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 explic-
itly deallocated using free(3) after use. If the buf argument is non-null it must point to
at least 33 characters of buffer space.
B. Kaliski, The MD2 Message-Digest Algorithm, RFC 1319.
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 a public domain implementation by Andrew Brown.
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
BSD September 24, 2005 BSD