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8a6db7e780
Imported libmd. This library contains MD2, MD4 and MD5. These three boggers pop up all over the place all of the time, so I decided we needed a library with them. In general they are used for security checks, so if you use them you want to link them static.
117 lines
3.2 KiB
Groff
117 lines
3.2 KiB
Groff
.\"
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.\" ----------------------------------------------------------------------------
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.\" "THE BEER-WARE LICENSE" (Revision 42):
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.\" <phk@login.dkuug.dk> wrote this file. As long as you retain this notice you
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.\" can do whatever you want with this stuff. If we meet some day, and you think
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.\" this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
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.\" ----------------------------------------------------------------------------
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.\"
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.\" $FreeBSD$
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.\"
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.Dd July 14, 1994
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.Dt MDX 3
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.Os FreeBSD 2
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.Sh NAME
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.Nm MDXInit ,
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.Nm MDXUpdate ,
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.Nm MDXFinal ,
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.Nm MDXEnd ,
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.Nm MDXFile ,
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.Nm MDXData .
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.Nd calculate ``MDX'' cryptographic checksum
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.Sh SYNOPSIS
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.Fd #include <mdX.h>
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.Ft void
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.Fn MDXInit "MDX_CTX *context"
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.Ft void
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.Fn MDXUpdate "MDX_CTX *context" "unsigned char *data" "unsigned int len"
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.Ft void
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.Fn MDXFinal "unsigned char digest[16]" "MDX_CTX *context"
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.Ft "char *"
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.Fn MDXEnd "MDX_CTX *context"
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.Ft "char *"
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.Fn MDXFile "char *filename"
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.Ft "char *"
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.Fn MDXData "unsigned char *data" "unsigned int len"
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.Sh DESCRIPTION
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The MDX functions calculate a 128-bit cryptographic checksum (digest)
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for any number of input bytes. A cryptographic checksum is a one-way
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hash-function, that is, you cannot find (except by exhaustive search)
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the input corresponding to a particular output. This net result is
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a ``fingerprint'' of the input-data, which doesn't disclose the actual
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input.
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MD2 is the slowest, MD4 is the fastest and MD5 is somewhere in the middle.
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MD2 can only be used for Privacy-Enhanced Mail.
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MD4 has been critizised for being to weak, and MD5 was developed as a
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response to this as ``MD4 with safety-belts''. If in doubt, use MD5.
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The
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.Fn MDXInit ,
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.Fn MDXUpdate
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and
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.Fn MDXFinal
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functions are the core functions. Allocate a MDX_CTX, initialize it with
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.Fn MDXInit
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run over the data with
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.Fn MDXUpdate
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and finally extract the result using
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.Fn MDXFinal .
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.Fn MDXEnd
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is identical to
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.Fn MDXFinal ,
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except the return is in ASCII-HEX in a
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string allocated with
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.Xr malloc 3 .
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.Fn MDXFile
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calculates the digest of a file, and returns the ASCII-HEX result.
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In case the file cannot be opened, NULL is returned.
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.Fn MDXData
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calculates the digest of a chunk of data in memory, and returns the ASCII-HEX
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result.
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When using
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.Fn MDXEnd ,
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.Fn MDXFile
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and
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.Fn MDXData ,
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the returned string must be explicitly deallocated using
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.Xr free 3
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after use.
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.Sh SEE ALSO
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.Xr md2 3 ,
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.Xr md4 3 ,
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.Xr md5 3
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.Pp
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ISOC
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Internet Request For Comments
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.%T RFC1319 ,
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.%T RFC1320
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and
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.%T RFC1321 .
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.Pp
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RSA Laboratories
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.%T Frequently Asked Questions About today's Cryptography .
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.Sh AUTHOR
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The MD2, MD4 and MD5 is designed and written by Ron Rivest and published in
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the above RFC's, including a reference implementation of each algorithm.
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This code is derived directly from these implementations by Poul-Henning Kamp
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<phk@login.dkuug.dk>
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Phk ristede runen.
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.Sh HISTORY
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These functions appeared in
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.Em FreeBSD-2.0
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.Sh BUGS
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No method is known to exist which finds two files having the same hash value,
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nor to find a file with a specific hash value.
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There is on the other hand no guarantee that such a method doesn't exist.
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MD2 can only be used for Privacy Enhanced Mail.
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Use MD4 or MD5 if that isn't what you're doing.
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.Sh COPYRIGHT
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