MD4(3) BSD Library Functions Manual MD4(3)
MD4Init, MD4Update, MD4Pad, MD4Final, MD4End, MD4File, MD4FileChunk, MD4Data -- calculate the RSA Data Security, Inc., ``MD4'' message digest
Message Digest (MD4, MD5, etc.) Support Library (libmd, -lmd)
MD4Update(MD4_CTX *context, const void *data, unsigned int len);
MD4Final(unsigned char digest, MD4_CTX *context);
MD4End(MD4_CTX *context, char *buf);
MD4File(const char *filename, char *buf);
MD4FileChunk(const char *filename, char *buf, off_t offset, off_t length);
MD4Data(const void *data, unsigned int len, char *buf);
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().
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 '