272a37e7b7
recent demonstration of a forged SSL certificate. Add text pointing out that SHA-1 is at least theoretically broken. Add a recommendation that new applications use SHA-256. MFC after: 1 month
141 lines
3.2 KiB
Groff
141 lines
3.2 KiB
Groff
.\" $FreeBSD$
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.Dd September 7, 2008
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.Dt MD5 1
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.Os
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.Sh NAME
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.Nm md5 , sha1 , sha256, rmd160
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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 md5
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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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.Nm sha1
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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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.Nm sha256
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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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.Nm rmd160
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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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The
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.Nm md5 , sha1 , sha256
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and
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.Nm rmd160
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utilities take as input a message of arbitrary length and produce as
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output a
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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
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.Tn MD5 , SHA-1 , SHA-256
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and
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.Tn RIPEMD-160
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algorithms are 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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.Tn RSA .
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.Pp
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.Tn MD5
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has been completely broken as far as finding collisions is
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concerned, and should not be relied upon to produce unique outputs.
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This also means that
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.Tn MD5
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should not be used as part of a cryptographic signature scheme.
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At the current time (2009-01-06) there is no publicly known method to
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"reverse" MD5, i.e., to find an input given a hash value.
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.Pp
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.Tn SHA-1
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currently (2009-01-06) has no known collisions, but an attack has been
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found which is faster than a brute-force search, placing the security of
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.Tn SHA-1
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in doubt.
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.Pp
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It is recommended that all new applications use
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.Tn SHA-256
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instead of one of the other hash functions.
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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 hexadecimal checksum of each file listed on the command line is printed
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after the options 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 append the checksum to stdout.
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.It Fl q
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Quiet mode - only the checksum 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 EXIT STATUS
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The
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.Nm md5 , sha1 , sha256
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and
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.Nm rmd160
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utilities exit 0 on success,
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and 1 if at least one of the input files could not be read.
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.Sh SEE ALSO
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.Xr cksum 1 ,
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.Xr md5 3 ,
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.Xr ripemd 3 ,
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.Xr sha 3 ,
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.Xr sha256 3
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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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.Rs
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.%A J. Burrows
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.%T The Secure Hash Standard
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.%O FIPS PUB 180-2
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.Re
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.Rs
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.%A D. Eastlake and P. Jones
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.%T US Secure Hash Algorithm 1
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.%O RFC 3174
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.Re
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.Pp
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RIPEMD-160 is part of the ISO draft standard
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.Qq ISO/IEC DIS 10118-3
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on dedicated hash functions.
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.Pp
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Secure Hash Standard (SHS):
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.Pa http://csrc.nist.gov/cryptval/shs.html .
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.Pp
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The RIPEMD-160 page:
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.Pa http://www.esat.kuleuven.ac.be/~bosselae/ripemd160.html .
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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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.Pp
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Support for SHA-1 and RIPEMD-160 has been added by
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.An Oliver Eikemeier Aq eik@FreeBSD.org .
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