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21f4052c5b
groff(1) has changed the internal layout for the .Lb doc strings, but to preserve backwards compatibility we cannot simply rename them, we need to create new aliases so that these will work with old and new macros. Signed-off-by: Guillem Jover <guillem@hadrons.org>
231 lines
5.5 KiB
Plaintext
231 lines
5.5 KiB
Plaintext
.\"
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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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.\" $MirOS: src/lib/libc/hash/mdX.3,v 1.4 2007/05/07 16:15:56 tg Exp $
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.\" $OpenBSD: mdX.3,v 1.9 2004/08/24 20:10:33 millert Exp $
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.\"
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.Dd April 29, 2004
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.Dt MDX 3bsd
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.Os
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.Sh NAME
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.Nm MDXInit ,
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.Nm MDXUpdate ,
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.Nm MDXPad ,
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.Nm MDXFinal ,
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.Nm MDXTransform ,
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.Nm MDXEnd ,
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.Nm MDXFile ,
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.Nm MDXFileChunk ,
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.Nm MDXData
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.Nd calculate the RSA Data Security, Inc., ``MDX'' message digest
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.Sh LIBRARY
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.ds str-Lb-libbsd Utility functions from BSD systems (libbsd, \-lbsd)
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.ds doc-str-Lb-libbsd \*[str-Lb-libbsd]
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.Lb libbsd
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.Sh SYNOPSIS
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.In sys/types.h
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.In mdX.h
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(See
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.Xr libbsd 7
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for include usage.)
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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" "const uint8_t *data" "size_t len"
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.Ft void
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.Fn MDXPad "MDX_CTX *context"
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.Ft void
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.Fn MDXFinal "uint8_t digest[MDX_DIGEST_LENGTH]" "MDX_CTX *context"
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.Ft void
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.Fn MDXTransform "uint32_t state[4]" "uint8_t block[MDX_BLOCK_LENGTH]"
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.Ft "char *"
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.Fn MDXEnd "MDX_CTX *context" "char *buf"
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.Ft "char *"
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.Fn MDXFile "const char *filename" "char *buf"
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.Ft "char *"
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.Fn MDXFileChunk "const char *filename" "char *buf" "off_t offset" "off_t length"
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.Ft "char *"
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.Fn MDXData "const uint8_t *data" "size_t len" "char *buf"
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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.
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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.
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This net result is a
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.Dq fingerprint
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of the input-data, which doesn't disclose the actual input.
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.Pp
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MD4 has been broken; it should only be used where necessary for
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backward compatibility.
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MD5 has not yet (1999-02-11) been broken, but recent attacks have cast
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some doubt on its security properties.
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The attacks on both MD4 and MD5
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are both in the nature of finding
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.Dq collisions
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\- that is, multiple
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inputs which hash to the same value; it is still unlikely for an attacker
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to be able to determine the exact original input given a hash value.
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.Pp
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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.
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Allocate an 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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.Pp
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The
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.Fn MDXPad
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function can be used to apply padding to the message digest as in
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.Fn MDXFinal ,
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but the current context can still be used with
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.Fn MDXUpdate .
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.Pp
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The
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.Fn MDXTransform
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function is used by
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.Fn MDXUpdate
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to hash 512-bit blocks and forms the core of the algorithm.
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Most programs should use the interface provided by
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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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instead of calling
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.Fn MDXTransform
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directly.
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.Pp
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.Fn MDXEnd
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is a wrapper for
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.Fn MDXFinal
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which converts the return value to an MDX_DIGEST_STRING_LENGTH-character
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(including the terminating '\e0')
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.Tn ASCII
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string which represents the 128 bits in hexadecimal.
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.Pp
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.Fn MDXFile
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calculates the digest of a file, and uses
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.Fn MDXEnd
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to return the result.
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If the file cannot be opened, a null pointer is returned.
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.Pp
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.Fn MDXFileChunk
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behaves like
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.Fn MDXFile
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but calculates the digest only for that portion of the file starting at
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.Fa offset
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and continuing for
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.Fa length
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bytes or until end of file is reached, whichever comes first.
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A zero
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.Fa length
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can be specified to read until end of file.
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A negative
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.Fa length
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or
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.Fa offset
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will be ignored.
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.Fn MDXData
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calculates the digest of a chunk of data in memory, and uses
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.Fn MDXEnd
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to return the result.
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.Pp
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When using
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.Fn MDXEnd ,
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.Fn MDXFile ,
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.Fn MDXFileChunk ,
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or
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.Fn MDXData ,
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the
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.Ar buf
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argument can be a null pointer, in which case the returned string
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is allocated with
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.Xr malloc 3
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and subsequently must be explicitly deallocated using
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.Xr free 3
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after use.
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If the
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.Ar buf
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argument is non-null it must point to at least MDX_DIGEST_STRING_LENGTH
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characters of buffer space.
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.Sh SEE ALSO
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.Xr cksum 1 ,
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.Xr md5 1 ,
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.Xr adler32 3 ,
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.Xr mdY 3 ,
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.Xr rmd160 3 ,
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.Xr sfv 3 ,
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.Xr sha1 3 ,
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.Xr sha2 3 ,
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.Xr suma 3 ,
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.Xr tiger 3 ,
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.Xr whirlpool 3
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.Rs
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.%A R. Rivest
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.%T The MD4 Message-Digest Algorithm
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.%O RFC 1186
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.Re
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.Rs
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.%A R. Rivest
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.%T The MD5 Message-Digest Algorithm
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.%O RFC 1321
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.Re
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.Rs
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.%A RSA Laboratories
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.%T Frequently Asked Questions About today's Cryptography
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.%O \&<http://www.rsa.com/rsalabs/faq/>
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.Re
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.Rs
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.%A H. Dobbertin
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.%T Alf Swindles Ann
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.%J CryptoBytes
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.%N 1(3):5
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.%D 1995
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.Re
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.Rs
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.%A MJ. B. Robshaw
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.%T On Recent Results for MD4 and MD5
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.%J RSA Laboratories Bulletin
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.%N 4
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.%D November 12, 1996
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.Re
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.Rs
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.%A Hans Dobbertin
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.%T Cryptanalysis of MD5 Compress
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.Re
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.Sh HISTORY
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These functions appeared in
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.Ox 2.0 .
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.Sh AUTHORS
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The original MDX routines were developed by
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.Tn RSA
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Data Security, Inc., and published in the above references.
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This code is derived from a public domain implementation written by Colin Plumb.
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.Pp
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The
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.Fn MDXEnd ,
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.Fn MDXFile ,
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.Fn MDXFileChunk ,
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and
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.Fn MDXData
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helper functions are derived from code written by Poul-Henning Kamp.
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.Sh BUGS
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Collisions have been found for the full versions of both MD4 and MD5
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as well as strong attacks against the SHA-0 and SHA-1 family.
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The use of
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.Xr sha2 3 ,
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or
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.Xr rmd160 3
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is recommended instead.
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