332 lines
8.8 KiB
Groff
332 lines
8.8 KiB
Groff
.\" $NetBSD: cksum.1,v 1.44 2012/06/25 02:32:12 riastradh Exp $
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.\"
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.\" Copyright (c) 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" the Institute of Electrical and Electronics Engineers, Inc.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)cksum.1 8.2 (Berkeley) 4/28/95
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.\"
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.Dd June 24, 2012
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.Dt CKSUM 1
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.Os
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.Sh NAME
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.Nm cksum ,
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.Nm md2 ,
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.Nm md4 ,
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.Nm md5 ,
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.Nm rmd160 ,
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.Nm sha1 ,
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.Nm sum
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.Nd display file checksums and block counts
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.Sh SYNOPSIS
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.Nm cksum
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.Op Fl n
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.Op Fl a Ar algorithm Oo Fl ptx Oc Oo Fl s Ar string Oc
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.Op Fl o Ar 1 Ns | Ns Ar 2
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.Op Ar Li \&| Fl c Oo Fl w Oc Oo Ar sumfile Oc
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.Nm sum
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.Op Fl n
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.Op Fl a Ar algorithm Oo Fl ptx Oc Oo Fl s Ar string Oc
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.Op Fl o Ar 1 Ns | Ns Ar 2
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.Op Ar Li \&| Fl c Oo Fl w Oc Oo Ar sumfile Oc
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.Nm md2
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.Op Fl nptx
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.Op Fl s Ar string
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.Op Ar Li \&| Fl c Oo Fl w Oc Oo Ar sumfile Oc
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.Nm md4
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.Op Fl nptx
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.Op Fl s Ar string
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.Op Ar Li \&| Fl c Oo Fl w Oc Oo Ar sumfile Oc
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.Nm md5
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.Op Fl nptx
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.Op Fl s Ar string
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.Op Ar Li \&| Fl c Oo Fl w Oc Oo Ar sumfile Oc
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.Nm rmd160
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.Op Fl nptx
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.Op Fl s Ar string
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.Op Ar Li \&| Fl c Oo Fl w Oc Oo Ar sumfile Oc
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.Nm sha1
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.Op Fl nptx
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.Op Fl s Ar string
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.Op Ar Li \&| Fl c Oo Fl w Oc Oo Ar sumfile Oc
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.Sh DESCRIPTION
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The
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.Nm
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utility writes to the standard output three whitespace separated
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fields for each input file.
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These fields are a checksum
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.Tn CRC ,
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the total number of octets in the file and the file name.
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If no file name is specified, the standard input is used and no file name
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is written.
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.Pp
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The
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.Nm sum
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utility is identical to the
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.Nm
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utility, except that it defaults to using historic algorithm 1, as
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described below.
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It is provided for compatibility only.
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.Pp
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The
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.Nm md2 ,
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.Nm md4 ,
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.Nm md5 ,
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.Nm sha1 ,
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and
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.Nm rmd160
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utilities compute cryptographic hash functions, and write to standard
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output the hexadecimal representation of the hash of their input.
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.Pp
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The options are as follows:
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.Bl -tag -width indent
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.It Fl a Ar algorithm
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When invoked as
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.Nm cksum ,
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use the specified
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.Ar algorithm .
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Valid algorithms are:
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.Bl -column -offset indent ".Sy Algorithm" ".Sy Bits" ".Sy Description"
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.It Sy Algorithm Ta Sy Bits Ta Sy Description
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.It Li CRC Ta 32 Ta Default CRC algorithm
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.It Li MD2 Ta 128 Ta MD2, per Li RFC1319
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.It Li MD4 Ta 128 Ta MD4, per Li RFC1320
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.It Li MD5 Ta 128 Ta MD5, per Li RFC1321
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.It Li RMD160 Ta 160 Ta RIPEMD-160
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.It Li SHA1 Ta 160 Ta SHA-1, per Li FIPS PUB 180-1
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.It Li SHA256 Ta 256 Ta SHA-2
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.It Li SHA384 Ta 384 Ta SHA-2
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.It Li SHA512 Ta 512 Ta SHA-2
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.It Li old1 Ta 16 Ta Algorithm 1, per Fl o Ar 1
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.It Li old2 Ta 16 Ta Algorithm 2, per Fl o Ar 2
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.El
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.It Fl c Op Ar sumfile
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Verify (check) files against a list of checksums.
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The list is read from
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.Ar sumfile ,
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or from stdin if no filename is given.
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E.g. first run
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.Dl Ic md5 *.tgz \*[Gt] MD5
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.Dl Ic sha1 *.tgz \*[Gt] SHA1
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to generate a list of MD5 checksums in
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.Pa MD5 ,
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then use the following command to verify them:
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.Dl Ic cat MD5 SHA1 | cksum -c
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If an error is found during checksum verification, an error
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message is printed, and the program returns an error code of 1.
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.It Fl o
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Use historic algorithms instead of the (superior) default one.
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.Pp
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Algorithm 1 is the algorithm used by historic
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.Bx
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systems as the
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.Xr sum 1
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algorithm and by historic
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.At V
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systems as the
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.Xr sum 1
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algorithm when using the
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.Fl r
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option.
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This is a 16-bit checksum, with a right rotation before each addition;
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overflow is discarded.
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.Pp
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Algorithm 2 is the algorithm used by historic
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.At V
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systems as the
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default
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.Xr sum 1
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algorithm.
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This is a 32-bit checksum, and is defined as follows:
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.Bd -unfilled -offset indent
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s = sum of all bytes;
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r = s % 2^16 + (s % 2^32) / 2^16;
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cksum = (r % 2^16) + r / 2^16;
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.Ed
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.Pp
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Both algorithm 1 and 2 write to the standard output the same fields as
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the default algorithm except that the size of the file in bytes is
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replaced with the size of the file in blocks.
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For historic reasons, the block size is 1024 for algorithm 1 and 512
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for algorithm 2.
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Partial blocks are rounded up.
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.It Fl w
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Print warnings about malformed checksum files when verifying
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checksums with
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.Fl c .
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.El
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.Pp
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The following options apply only when using the one of the message
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digest algorithms:
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.Bl -tag -width indent
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.It Fl n
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Print the hash and the filename in the normal sum output form, with
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the hash at the left and the filename following on the right.
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.It Fl p
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Echo input from standard input to standard output, and append the
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selected message digest.
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.It Fl s Ar string
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Print the hash of the given string
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.Ar string .
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.It Fl t
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Run a built-in message digest time trial.
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.It Fl x
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Run a built-in message digest test script.
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The tests that are run
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are supposed to encompass all the various tests in the suites that
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accompany the algorithms' descriptions with the exception of the
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last test for the SHA-1 algorithm and the RIPEMD-160 algorithm.
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The
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last test for these is one million copies of the lower letter a.
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.El
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.Pp
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The default
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.Tn CRC
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used is based on the polynomial used for
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.Tn CRC
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error checking
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in the networking standard
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.St -iso8802-3 .
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The
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.Tn CRC
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checksum encoding is defined by the generating polynomial:
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.Pp
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.Bd -unfilled -offset indent
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G(x) = x^32 + x^26 + x^23 + x^22 + x^16 + x^12 +
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x^11 + x^10 + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1
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.Ed
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.Pp
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Mathematically, the
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.Tn CRC
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value corresponding to a given file is defined by
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the following procedure:
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.Bd -filled -offset indent
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The
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.Ar n
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bits to be evaluated are considered to be the coefficients of a mod 2
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polynomial M(x) of degree
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.Ar n Ns \-1 .
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These
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.Ar n
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bits are the bits from the file, with the most significant bit being the most
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significant bit of the first octet of the file and the last bit being the least
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significant bit of the last octet, padded with zero bits (if necessary) to
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achieve an integral number of octets, followed by one or more octets
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representing the length of the file as a binary value, least significant octet
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first.
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The smallest number of octets capable of representing this integer are used.
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.Pp
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M(x) is multiplied by x^32 (i.e., shifted left 32 bits) and divided by
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G(x) using mod 2 division, producing a remainder R(x) of degree \*[Le] 31.
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.Pp
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The coefficients of R(x) are considered to be a 32-bit sequence.
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.Pp
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The bit sequence is complemented and the result is the CRC.
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.Ed
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.Pp
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The
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.Nm
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and
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.Nm sum
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utilities exit 0 on success, and \*[Gt]0 if an error occurs.
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.Sh SEE ALSO
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.Xr openssl 1 ,
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.Xr mtree 8
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.Pp
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The default calculation is identical to that given in pseudo-code
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in the following
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.Tn ACM
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article.
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.Rs
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.%T "Computation of Cyclic Redundancy Checks Via Table Lookup"
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.%A Dilip V. Sarwate
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.%J "Communications of the \*(tNACM\*(sP"
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.%D "August 1988"
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.Re
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.Rs
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.%A R. Rivest
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.%T The MD2 Message-Digest Algorithm
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.%O RFC 1319
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.Re
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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 and RFC 1320
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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 U.S. DOC/NIST
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.%T Secure Hash Standard
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.%O FIPS PUB 180-1
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.Re
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.Sh STANDARDS
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The
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.Nm
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utility is expected to conform to
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.St -p1003.1-2004 .
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.Sh HISTORY
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The
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.Nm
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utility appeared in
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.Bx 4.4 .
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.Nm md5
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was added in
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.Nx 1.3 .
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The functionality for
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.Nm md2 ,
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.Nm md4 ,
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.Nm sha1 ,
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and
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.Nm rmd160
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was added in
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.Nx 1.6 .
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Support for the SHA-2 algorithms
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.Po
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.Li SHA256 ,
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.Li SHA384 ,
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and
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.Li SHA512
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.Pc
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was added in
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.Nx 3.0 .
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The functionality to verify checksum stored in a file
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.Pq Fl c
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first appeared in
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.Nx 4.0 .
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.\" .Pp
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.\" The
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.\" .Nm sum
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.\" utility appeared in
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.\" .Bx ?.?
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.\" and
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.\" .At V .
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