Manual Reference Pages - MD5FILE (3)
- calculate the RSA Data Security, Inc., MD5 message digest
MD5Init MD5_CTX *context
MD5Update MD5_CTX *context const void *data unsigned int len
MD5Pad MD5_CTX *context
MD5Final unsigned char digest MD5_CTX *context
MD5End MD5_CTX *context char *buf
MD5File const char *filename char *buf
MD5FileChunk const char *filename char *buf off_t offset off_t length
MD5Data const void *data unsigned int len char *buf
The MD5 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
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
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
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.
functions are the core functions.
.Vt MD5_CTX ,
initialize it with
run over the data with
and finally extract the result using
function can be used to pad message data in same way
as done by
without terminating calculation.
function is a wrapper for
which converts the return value to a 33-character
(including the terminating \0)
string which represents the 128 bits in hexadecimal.
function calculates the digest of a file, and uses
to return the result.
If the file cannot be opened, a null pointer is returned.
function is similar to
but it only calculates the digest over a byte-range of the file specified,
parameter is specified as 0, or more than the length of the remaining part
of the file,
calculates the digest from
to the end of file.
function calculates the digest of a chunk of data in memory, and uses
to return the result.
argument can be a null pointer, in which case the returned string
is allocated with
and subsequently must be explicitly deallocated using
argument is non-null it must point to at least 33 characters of buffer space.
The MD4 Message-Digest Algorithm
The MD5 Message-Digest Algorithm
Alf Swindles Ann
On Recent Results for MD2, MD4 and MD5
These functions appeared in
.Fx 2.0 .
The original MD5 routines were developed by
Data Security, Inc., and published in the above references.
This code is derived directly from these implementations by
.An Poul-Henning Kamp Aq phk@FreeBSD.org
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 does not exist.
Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
License to copy and use this software is granted provided that it
is identified as the "RSA Data Security, Inc. MD5 Message-Digest
Algorithm" in all material mentioning or referencing this software
or this function.
License is also granted to make and use derivative works provided
that such works are identified as "derived from the RSA Data
Security, Inc. MD5 Message-Digest Algorithm" in all material
mentioning or referencing the derived work.
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
documentation and/or software.
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