1780e40715
This implements SHA-512/256, which generates a 256 bit hash by calculating the SHA-512 then truncating the result. A different initial value is used, making the result different from the first 256 bits of the SHA-512 of the same input. SHA-512 is ~50% faster than SHA-256 on 64bit platforms, so the result is a faster 256 bit hash. The main goal of this implementation is to enable support for this faster hashing algorithm in ZFS. The feature was introduced into ZFS in r289422, but is disconnected because SHA-512/256 support was missing. A further commit will enable it in ZFS. This is the follow on to r292782 Reviewed by: cem Sponsored by: ScaleEngine Inc. Differential Revision: https://reviews.freebsd.org/D6061
178 lines
4.0 KiB
Groff
178 lines
4.0 KiB
Groff
.\" $FreeBSD$
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.Dd April 22, 2016
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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 , sha384 , sha512, sha512t256, 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 c Ar string
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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 c Ar string
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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 c Ar string
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.Op Fl s Ar string
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.Op Ar
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.Nm sha384
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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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.Nm sha512
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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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.Nm sha512t256
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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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.Nm rmd160
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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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.Sh DESCRIPTION
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The
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.Nm md5 , sha1 , sha256 , sha384 , sha512, sha512t256
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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 , SHA-384 , SHA-512
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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 (2014-05-17) there is no publicly known method to
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.Dq reverse
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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 (2014-05-17) 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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.Tn SHA-512t256
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is a version of
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.Tn SHA-512
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truncated to only 256 bits.
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On 64-bit hardware, this algorithm is approximately 50% faster than
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.Tn SHA-256
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but with the same level of security.
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The hashes are not interchangeable.
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.Pp
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It is recommended that all new applications use
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.Tn SHA-512
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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 c Ar string
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Compare the digest of the file against this string.
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.Pq Note that this option is not yet useful if multiple files are specified.
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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 \(em 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 , sha512, sha512t256
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and
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.Nm rmd160
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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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.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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.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 Mt eik@FreeBSD.org .
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