79 lines
1.9 KiB
Groff
79 lines
1.9 KiB
Groff
.\" $FreeBSD$
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.Dd February 14, 1994
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.Dt MD5 1
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.Os
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.Sh NAME
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.Nm md5
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.Nd calculate a message-digest fingerprint (checksum) for a file
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.Sh SYNOPSIS
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.Nm
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.Op Fl pqrtx
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.Op Fl s Ar string
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.Op Ar
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.Sh DESCRIPTION
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.Nm Md5
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takes as input a message of arbitrary length and produces
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as output a 128-bit
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.Dq fingerprint
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or
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.Dq message digest
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of the input.
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It is conjectured that it is computationally infeasible to
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produce two messages having the same message digest, or to produce any
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message having a given prespecified target message digest.
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The MD5 algorithm is intended for digital signature applications, where a
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large file must be
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.Dq compressed
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in a secure manner before being encrypted with a private
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(secret)
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key under a public-key cryptosystem such as
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.Em RSA .
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.Pp
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MD5 has not yet (2001-09-03) been broken, but sufficient attacks have been
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made that its security is in some doubt.
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The attacks on MD5
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are in the nature of finding
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.Dq collisions
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\(em 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 following options may be used in any combination and must
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precede any files named on the command line.
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The MD5
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sum of each file listed on the command line is printed after the options
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are processed.
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.Bl -tag -width indent
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.It Fl s Ar string
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Print a checksum of the given
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.Ar string .
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.It Fl p
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Echo stdin to stdout and appends the MD5 sum to stdout.
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.It Fl q
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Quiet mode - only the MD5 sum is printed out.
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Overrides the
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.Fl r
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option.
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.It Fl r
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Reverses the format of the output.
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This helps with visual diffs.
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Does nothing
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when combined with the
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.Fl ptx
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options.
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.It Fl t
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Run a built-in time trial.
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.It Fl x
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Run a built-in test script.
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.El
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.Sh SEE ALSO
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.Xr cksum 1
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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 RFC1321
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.Re
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.Sh ACKNOWLEDGMENTS
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This program is placed in the public domain for free general use by
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RSA Data Security.
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