202 lines
6.4 KiB
Groff
202 lines
6.4 KiB
Groff
.\" $OpenBSD: cksum.1,v 1.42 2023/10/31 20:42:14 millert 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 $Mdocdate: October 31 2023 $
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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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.Nd display file checksums and block counts
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.Sh SYNOPSIS
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.Nm cksum
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.Bk -words
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.Op Fl bcpqrtx
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.Op Fl a Ar algorithms
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.Op Fl C Ar checklist
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.Op Fl h Ar hashfile
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.Op Fl s Ar string
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.Op Ar
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.Ek
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.Sh DESCRIPTION
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The
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.Nm cksum
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utility writes to the standard output a single line for each input file.
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The format of this line varies with the algorithm being used as follows:
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.Bl -tag -width allxothers
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.It cksum
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The output line consists of three whitespace separated fields:
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a CRC checksum, the number of octets in the input,
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and name of the file or string.
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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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.It all others
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Unless the
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.Fl r
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option is specified (see below),
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output lines consist of four whitespace separated fields:
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the name of the algorithm used, the name of the file or string in
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parentheses, an equals sign, and the cryptographic hash of the input.
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If no file name is specified, the standard input is used and only
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the cryptographic hash is output.
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.El
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.Pp
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The options are as follows:
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.Bl -tag -width Ds
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.It Fl a Ar algorithms
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Use the specified algorithm(s) instead of the default (cksum).
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Supported algorithms include cksum, md5, rmd160, sha1,
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sha224, sha256, sha384, sha512/256, and sha512.
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Multiple algorithms may be specified, separated by a comma or whitespace.
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Additionally, multiple
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.Fl a
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options may be specified on the command line.
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Case is ignored when matching algorithms.
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The output format may be specified on a per-algorithm basis
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by using a single-character suffix, e.g.\&
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.Dq sha256b .
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If the algorithm has a
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.Sq b
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suffix, the checksum will be output in base64 format.
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If the algorithm has an
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.Sq x
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suffix, the checksum will be output in hex format.
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If an algorithm with the same output format is repeated,
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only the first instance is used.
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Note that output format suffixes are not supported
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for the cksum algorithm.
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.It Fl b
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Output checksums in base64 notation, not hexadecimal by
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default.
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A
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.Sq b
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or
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.Sq x
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suffix on the algorithm will override this default.
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This option is ignored for the cksum algorithm.
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.It Fl C Ar checklist
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Compare the checksum of each
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.Ar file
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against the checksums in the
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.Ar checklist .
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Any specified
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.Ar file
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that is not listed in the
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.Ar checklist
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will generate an error.
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.It Fl c
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If this option is specified, the
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.Ar file
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options become checklists.
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Each checklist should contain hash results, which will be verified
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against the specified paths.
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Both normal (BSD) and reverse (GNU) forms are supported in either
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hexadecimal or base64 format.
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Output consists of the digest used, the file name,
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and an OK, FAILED, or MISSING for the result of the comparison.
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Entries in normal format can be validated using any of the supported checksums.
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Entries in reverse format are validated using the specified algorithm
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(or the default algorithm if none is specified).
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If no file is given, stdin is used.
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The
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.Fl c
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option may not be used in conjunction with more than a single
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.Fl a
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option.
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.It Fl h Ar hashfile
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Place the checksum into
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.Ar hashfile
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instead of stdout.
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.It Fl p
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Echo stdin to stdout and append the
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checksum to stdout.
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.It Fl q
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Only print the checksum (quiet mode) or if used in conjunction with the
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.Fl c
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flag, only print the failed cases.
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.It Fl r
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Reverse the format of the hash algorithm output, similar to
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the checksum output format (but without the number of octets).
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This is also the format used by the GNU
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.Nm cksum
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utility.
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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 t
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Run a built-in time trial.
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Specifying
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.Fl t
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multiple times results in the number of rounds being multiplied
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by 10 for each additional flag.
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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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.Pp
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The default CRC used is based on the polynomial used for CRC error checking
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in the networking standard
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ISO/IEC 8802-3:1996.
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The other available algorithms are described in their respective
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man pages in section 3 of the manual.
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.Sh EXIT STATUS
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.Ex -std cksum
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.Sh SEE ALSO
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.Xr md5 1
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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 ACM 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 ACM"
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.%D "August 1988"
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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 compliant with the
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.St -p1003.1-2008
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specification.
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.Pp
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All the flags are extensions to that specification.
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.Sh HISTORY
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The
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.Nm cksum
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utility appeared in
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.Bx 4.3 Net/2 .
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.Sh CAVEATS
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Do not use the cksum or md5 algorithms to verify file integrity.
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An attacker can trivially produce modified payload that
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has the same checksum as the original version.
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Use a cryptographic checksum instead.
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