434 lines
12 KiB
Groff
434 lines
12 KiB
Groff
.Dd May 10, 2023
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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 , sha224 , sha256 , sha384 ,
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.Nm sha512 , sha512t224 , sha512t256 ,
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.Nm rmd160 , skein256 , skein512 , skein1024 ,
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.Nm md5sum , sha1sum , sha224sum , sha256sum , sha384sum ,
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.Nm sha512sum , sha512t224sum , sha512t256sum ,
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.Nm rmd160sum , skein256sum , skein512sum , skein1024sum ,
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.Nm shasum
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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 c Ar string
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.Op Fl s Ar string
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.Op Ar
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.Pp
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.Nm md5sum
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.Op Fl bctwz
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.Op Fl -binary
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.Op Fl -check
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.Op Fl -help
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.Op Fl -ignore-missing
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.Op Fl -quiet
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.Op Fl -status
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.Op Fl -strict
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.Op Fl -tag
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.Op Fl -text
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.Op Fl -version
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.Op Fl -warn
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.Op Fl -zero
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.Op Ar
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.Pp
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(All other hashes have the same options and usage.)
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.Pp
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.Nm shasum
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.Op Fl 0bchqstUvw
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.Op Fl -01
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.Op Fl a | -algorithm Ar alg
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.Op Fl -binary
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.Op Fl -check
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.Op Fl -help
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.Op Fl -ignore-missing
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.Op Fl -quiet
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.Op Fl -status
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.Op Fl -strict
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.Op Fl -tag
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.Op Fl -text
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.Op Fl -UNIVERSAL
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.Op Fl -version
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.Op Fl -warn
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.Op Ar
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.Sh DESCRIPTION
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The
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.Nm md5 , sha1 , sha224 , sha256 , sha384 , sha512 , sha512t224 , sha512t256 ,
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.Nm rmd160 , skein256 , skein512 ,
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and
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.Nm skein1024
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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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.Pp
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The
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.Nm md5sum , sha1sum , sha224sum , sha256sum , sha384sum , sha512sum ,
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.Nm sha512t224sum , sha512t256sum , rmd160sum , skein256sum , skein512sum ,
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and
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.Nm skein1024sum
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utilities do the same, but with command-line options and an output
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format that match those of their similary named GNU utilities.
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.Pp
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The
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.Nm shasum
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utility does the same, but with command-line options and an output
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format that match those of the similarly named utility that ships with
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Perl.
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.Pp
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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 SHA-224 , SHA-256 , SHA-384 , SHA-512, RIPEMD-160,
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and SKEIN
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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 RSA.
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.Pp
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The MD5 and SHA-1 algorithms have been proven to be vulnerable to practical
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collision attacks and should not be relied upon to produce unique outputs,
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.Em nor should they be used as part of a cryptographic signature scheme.
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As of 2017-03-02, there is no publicly known method to
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.Em reverse
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either algorithm, i.e., to find an input that produces a specific
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output.
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.Pp
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SHA-512t256 is a version of SHA-512 truncated to only 256 bits.
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On 64-bit hardware, this algorithm is approximately 50% faster than SHA-256 but
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with the same level of security.
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The hashes are not interchangeable.
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.Pp
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SHA-512t224 is identical to SHA-512t256, but with the digest truncated
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to 224 bits.
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.Pp
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It is recommended that all new applications use SHA-512 or SKEIN-512
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instead of one of the other hash functions.
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.Ss BSD OPTIONS
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The following options are available in BSD mode, i.e. when the program
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is invoked with a name that does not end in
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.Dq sum :
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.Bl -tag -width indent
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.It Fl c Ar string , Fl -check= Ns Ar string
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Compare the digest of the file against this string.
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If combined with the
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.Fl q
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or
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.Fl -quiet
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option, the calculated digest is printed in addition to the exit status being set.
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.Pq Note that this option is not yet useful if multiple files are specified.
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.It Fl p , -passthrough
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Echo stdin to stdout and append the checksum to stdout.
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.It Fl q , -quiet
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Quiet mode \(em only the checksum is printed out.
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Overrides the
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.Fl r
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or
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.Fl -reverse
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option.
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.It Fl r , -reverse
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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 s Ar string , Fl -string= Ns 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 , Fl -time-trial
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Run a built-in time trial.
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For the
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.Nm -sum
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versions, this is a nop for compatibility with coreutils.
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.It Fl x , Fl -self-test
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Run a built-in test script.
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.El
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.Ss GNU OPTIONS
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The following options are available in GNU mode, i.e. when the program
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is invoked with a name that ends in
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.Dq sum :
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.Bl -tag -width indent
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.It Fl b , Fl -binary
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Read files in binary mode.
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.It Fl c , Fl -check
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The file passed as arguments must contain digest lines generated by the same
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digest algorithm in either classical BSD format or in GNU coreutils format.
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A line with the file name followed by a colon
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.Dq ":"
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and either OK or FAILED is written for each well-formed line in the digest file.
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If applicable, the number of failed comparisons and the number of lines that were
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skipped since they were not well-formed are printed at the end.
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The
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.Fl -quiet
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option can be used to quiesce the output unless there are mismatched entries in
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the digest.
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.It Fl -help
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Print a usage message and exit.
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.It Fl -ignore-missing
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When verifying checksums, ignore files for which checksums are given
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but which aren't found on disk.
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.It Fl -quiet
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When verifying checksums, do not print anything unless the
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verification fails.
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.It Fl -status
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When verifying checksums, do not print anything at all.
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The exit code will reflect whether verification succeeded.
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.It Fl -strict
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When verifying checksums, fail if the input is malformed.
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.It Fl -tag
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Produce BSD-style output.
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.It Fl t , Fl -text
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Read files in text mode.
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This is the default.
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Note that this implementation does not differentiate between binary
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and text mode.
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.It Fl -version
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Print version information and exit.
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.It Fl w , Fl -warn
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When verifying checksums, warn about malformed input.
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.It Fl z , Fl -zero
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Terminate output lines with NUL rather than with newline.
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.El
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.Ss PERL OPTIONS
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The following options are available in Perl mode, i.e. when the program
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is invoked with the name
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.Dq shasum :
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.Bl -tag -width indent
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.It Fl 0 , Fl -01
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Read files in bits mode: ASCII
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.Sq 0
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and
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.Sq 1
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characters correspond to 0 and 1 bits, respectively, and all other
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characters are ignored.
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See
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.Sx BUGS .
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.It Fl a Ar alg , Fl -algorithm Ar alg
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Use the specified algorithm:
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.Dq 1
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for SHA-1 (default),
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.Dq xxx
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for
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.Va xxx Ns -bit
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SHA-2 (e.g.
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.Dq 256
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for SHA-256)
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or
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.Dq xxxyyy
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for
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.Va xxx Ns -bit
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SHA-2 truncated to
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.Va yyy
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bits (e.g.
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.Dq 512224
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for SHA-512/224).
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.It Fl b , Fl -binary
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Read files in binary mode.
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.It Fl c , Fl -check
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The file passed as arguments must contain digest lines generated by the same
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digest algorithm in either classical BSD format or in GNU coreutils format.
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A line with the file name followed by a colon
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.Dq ":"
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and either OK or FAILED is written for each well-formed line in the digest file.
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If applicable, the number of failed comparisons and the number of lines that were
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skipped since they were not well-formed are printed at the end.
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The
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.Fl -quiet
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option can be used to quiesce the output unless there are mismatched entries in
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the digest.
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.It Fl -help
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Print a usage message and exit.
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.It Fl -ignore-missing
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When verifying checksums, ignore files for which checksums are given
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but which aren't found on disk.
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.It Fl -quiet
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When verifying checksums, do not print anything unless the
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verification fails.
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.It Fl -status
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When verifying checksums, do not print anything at all.
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The exit code will reflect whether verification succeeded.
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.It Fl -strict
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When verifying checksums, fail if the input is malformed.
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.It Fl -tag
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Produce BSD-style output.
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.It Fl t , Fl -text
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Read files in text mode.
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This is the default.
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Note that this implementation does not differentiate between binary
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and text mode.
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.It Fl U , Fl -UNIVERSAL
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Read files in universal mode: any CR-LF pair, as well as any CR not
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followed by LF, is translated to LF before the digest is computed.
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.It Fl -version
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Print version information and exit.
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.It Fl w , Fl -warn
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When verifying checksums, warn about malformed input.
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.El
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.Sh EXIT STATUS
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The
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.Nm md5 , sha1 , sha224 , sha256 , sha384 , sha512 ,
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.Nm sha512t224 , sha512t256 ,
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.Nm rmd160 , skein256 , skein512 ,
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and
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.Nm skein1024
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utilities exit 0 on success,
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1 if at least one of the input files could not be read,
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and 2 if at least one file does not have the same hash as the
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.Fl c
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option.
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.Pp
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The
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.Nm md5sum , sha1sum , sha224sum , sha256sum , sha384sum , sha512sum ,
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.Nm sha512t224sum , sha512t256sum ,
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.Nm rmd160 , skein256 , skein512 , skein1024
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and
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.Nm shasum
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utilities exit 0 on success and 1 if at least one of the input files
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could not be read or, when verifying checksums, does not have the
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expected checksum.
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.Sh EXAMPLES
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Calculate the MD5 checksum of the string
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.Dq Hello .
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.Bd -literal -offset indent
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$ md5 -s Hello
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MD5 ("Hello") = 8b1a9953c4611296a827abf8c47804d7
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.Ed
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.Pp
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Same as above, but note the absence of the newline character in the input
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string:
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.Bd -literal -offset indent
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$ echo -n Hello | md5
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8b1a9953c4611296a827abf8c47804d7
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.Ed
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.Pp
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Calculate the checksum of multiple files reversing the output:
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.Bd -literal -offset indent
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$ md5 -r /boot/loader.conf /etc/rc.conf
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ada5f60f23af88ff95b8091d6d67bef6 /boot/loader.conf
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d80bf36c332dc0fdc479366ec3fa44cd /etc/rc.conf
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.Ed
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.Pp
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This is almost but not quite identical to the output from GNU mode:
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.Bd -literal -offset indent
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$ md5sum /boot/loader.conf /etc/rc.conf
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ada5f60f23af88ff95b8091d6d67bef6 /boot/loader.conf
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d80bf36c332dc0fdc479366ec3fa44cd /etc/rc.conf
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.Ed
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.Pp
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Note the two spaces between hash and file name.
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If binary mode is requested, they are instead separated by a space and
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an asterisk:
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.Bd -literal -offset indent
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$ md5sum -b /boot/loader.conf /etc/rc.conf
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ada5f60f23af88ff95b8091d6d67bef6 */boot/loader.conf
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d80bf36c332dc0fdc479366ec3fa44cd */etc/rc.conf
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.Ed
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.Pp
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Write the digest for
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.Pa /boot/loader.conf
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in a file named
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.Pa digest .
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Then calculate the checksum again and validate it against the checksum string
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extracted from the
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.Pa digest
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file:
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.Bd -literal -offset indent
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$ md5 /boot/loader.conf > digest && md5 -c $(cut -f2 -d= digest) /boot/loader.conf
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MD5 (/boot/loader.conf) = ada5f60f23af88ff95b8091d6d67bef6
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.Ed
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.Pp
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Same as above but comparing the digest against an invalid string
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.Pq Dq randomstring ,
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which results in a failure.
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.Bd -literal -offset indent
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$ md5 -c randomstring /boot/loader.conf
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MD5 (/boot/loader.conf) = ada5f60f23af88ff95b8091d6d67bef6 [ Failed ]
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.Ed
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.Pp
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In GNU mode, the
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.Fl c
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option does not compare against a hash string passed as parameter.
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Instead, it expects a digest file, as created under the name
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.Pa digest
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for
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.Pa /boot/loader.conf
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in the example above.
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.Bd -literal -offset indent
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$ md5 -c digest /boot/loader.conf
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/boot/loader.conf: OK
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.Ed
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.Pp
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The digest file may contain any number of lines in the format
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generated in either BSD or GNU mode.
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If a hash value does not match the file,
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.Dq FAILED
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is printed instead of
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.Dq OK .
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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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.Xr sha384 3 ,
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.Xr sha512 3 ,
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.Xr skein 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 https://www.nist.gov/publications/secure-hash-standard-shs
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.Pp
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The RIPEMD-160 page:
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.Pa https://homes.esat.kuleuven.be/~bosselae/ripemd160.html
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.Sh BUGS
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In bits mode, the original
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.Nm shasum
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script is capable of processing inputs of arbitrary length.
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This implementation is not, and will issue an error if the input
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length is not a multiple of eight bits.
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.Sh ACKNOWLEDGMENTS
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.An -nosplit
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This utility was originally derived from a program which was placed in
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the public domain for free general use by RSA Data Security.
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.Pp
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Support for SHA-1 and RIPEMD-160 was added by
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.An Oliver Eikemeier Aq Mt eik@FreeBSD.org .
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.Pp
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Support for SHA-2 was added by
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.An Colin Percival Aq Mt cperciva@FreeBSD.org
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and
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.An Allan Jude Aq Mt allanjude@FreeBSD.org .
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.Pp
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Support for SKEIN was added by
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.An Allan Jude Aq Mt allanjude@FreeBSD.org .
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.Pp
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Compatibility with GNU coreutils was added by
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.An Warner Losh Aq Mt imp@FreeBSD.org
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and much expanded by
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.An Dag-Erling Sm\(/orgrav Aq Mt des@FreeBSD.org ,
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who also added Perl compatibility.
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