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CKSUM(1)		FreeBSD	General	Commands Manual		      CKSUM(1)

NAME
     cksum, md2, md4, md5, rmd160, sha1, sum --	display	file checksums and
     block counts

SYNOPSIS
     cksum [-n]	[-a algorithm [-pqtx] [-s string]] [-o 1|2]
	   [file ... | -c [-w] [sumfile]]
     sum [-n] [-a algorithm [-pqtx] [-s	string]] [-o 1|2]
	   [file ... | -c [-w] [sumfile]]
     md2 [-npqtx] [-s string] [file ...	| -c [-w] [sumfile]]
     md4 [-npqtx] [-s string] [file ...	| -c [-w] [sumfile]]
     md5 [-npqtx] [-s string] [file ...	| -c [-w] [sumfile]]
     rmd160 [-npqtx] [-s string] [file ... | -c	[-w] [sumfile]]
     sha1 [-npqtx] [-s string] [file ... | -c [-w] [sumfile]]

DESCRIPTION
     The cksum utility writes to the standard output three whitespace sepa-
     rated fields for each input file.	These fields are a checksum CRC, the
     total number of octets in the file	and the	file name.  If no file name is
     specified,	the standard input is used and no file name is written.

     The sum utility is	identical to the cksum utility,	except that it de-
     faults to using historic algorithm	1, as described	below.	It is provided
     for compatibility only.

     The md2, md4, md5,	sha1, and rmd160 utilities compute cryptographic hash
     functions,	and write to standard output the hexadecimal representation of
     the hash of their input.

     The options are as	follows:

     -a	algorithm
	     When invoked as cksum, use	the specified algorithm.  Valid	algo-
	     rithms are:

		   Algorithm	Bits	Description
		   CRC		32	Default	CRC algorithm
		   MD2		128	MD2, per RFC1319
		   MD4		128	MD4, per RFC1320
		   MD5		128	MD5, per RFC1321
		   RMD160	160	RIPEMD-160
		   SHA1		160	SHA-1, per FIPS	PUB 180-1
		   SHA256	256	SHA-2
		   SHA384	384	SHA-2
		   SHA512	512	SHA-2
		   old1		16	Algorithm 1, per -o 1
		   old2		16	Algorithm 2, per -o 2

     -c	[sumfile]
	     Verify (check) files against a list of checksums.	The list is
	     read from sumfile,	or from	stdin if no filename is	given.	E.g.
	     first run
		   md5 *.tgz > MD5
		   sha1	*.tgz >	SHA1
	     to	generate a list	of MD5 checksums in MD5, then use the follow-
	     ing command to verify them:
		   cat MD5 SHA1	| cksum	-c
	     If	an error is found during checksum verification,	an error mes-
	     sage is printed, and the program returns an error code of 1.

     -o	     Use historic algorithms instead of	the (superior) default one.

	     Algorithm 1 is the	algorithm used by historic BSD systems as the
	     sum(1) algorithm and by historic AT&T System V UNIX systems as
	     the sum(1)	algorithm when using the -r option.  This is a 16-bit
	     checksum, with a right rotation before each addition; overflow is
	     discarded.

	     Algorithm 2 is the	algorithm used by historic AT&T	System V UNIX
	     systems as	the default sum(1) algorithm.  This is a 32-bit	check-
	     sum, and is defined as follows:

		   s = sum of all bytes;
		   r = s % 2^16	+ (s % 2^32) / 2^16;
		   cksum = (r %	2^16) +	r / 2^16;

	     Both algorithm 1 and 2 write to the standard output the same
	     fields as the default algorithm except that the size of the file
	     in	bytes is replaced with the size	of the file in blocks.	For
	     historic reasons, the block size is 1024 for algorithm 1 and 512
	     for algorithm 2.  Partial blocks are rounded up.

     -w	     Print warnings about malformed checksum files when	verifying
	     checksums with -c.

     The following options apply only when using the one of the	message	digest
     algorithms:

     -n	     Print the hash and	the filename in	the normal sum output form,
	     with the hash at the left and the filename	following on the
	     right.

     -p	     Echo input	from standard input to standard	output,	and append the
	     selected message digest.

     -q	     Quiet mode	-- only	the checksum is	printed	out.  Overrides	the -n
	     option.

     -s	string
	     Print the hash of the given string	string.

     -t	     Run a built-in message digest time	trial.

     -x	     Run a built-in message digest test	script.	 The tests that	are
	     run are supposed to encompass all the various tests in the	suites
	     that accompany the	algorithms' descriptions with the exception of
	     the last test for the SHA-1 algorithm and the RIPEMD-160 algo-
	     rithm.  The last test for these is	one million copies of the
	     lower letter a.

     The default CRC used is based on the polynomial used for CRC error	check-
     ing in the	networking standard ISO/IEC 8802-3:1989.  The CRC checksum en-
     coding is defined by the generating polynomial:

	   G(x)	= x^32 + x^26 +	x^23 + x^22 + x^16 + x^12 +
		x^11 + x^10 + x^8 + x^7	+ x^5 +	x^4 + x^2 + x +	1

     Mathematically, the CRC value corresponding to a given file is defined by
     the following procedure:

	   The n bits to be evaluated are considered to	be the coefficients of
	   a  mod  2 polynomial	M(x) of	degree n-1.  These n bits are the bits
	   from	the file, with the most	significant bit	being the most signif-
	   icant bit of	the first octet	of the file and	the last bit being the
	   least significant bit of the	last octet, padded with	zero bits  (if
	   necessary) to achieve an integral number of octets, followed	by one
	   or more octets representing the length of  the  file	 as  a	binary
	   value,  least  significant  octet  first.   The  smallest number of
	   octets capable of representing this integer are used.

	   M(x)	is multiplied by x^32 (i.e., shifted left 32 bits) and divided
	   by  G(x) using mod 2	division, producing a remainder	R(x) of	degree
	   <= 31.

	   The coefficients of R(x) are	considered to be a 32-bit sequence.

	   The bit sequence is complemented and	the result is the CRC.

     The cksum and sum utilities exit 0	on success, and	>0 if an error occurs.

SEE ALSO
     openssl(1), mtree(8)

     The default calculation is	identical to that given	in pseudo-code in the
     following ACM article.

     Dilip V. Sarwate, "Computation of Cyclic Redundancy Checks	Via Table
     Lookup", Communications of	the ACM, August	1988.

     R.	Rivest,	The MD2	Message-Digest Algorithm, RFC 1319.

     R.	Rivest,	The MD4	Message-Digest Algorithm, RFC 1186 and RFC 1320.

     R.	Rivest,	The MD5	Message-Digest Algorithm, RFC 1321.

     U.S. DOC/NIST, Secure Hash	Standard, FIPS PUB 180-1.

STANDARDS
     The cksum utility is expected to conform to IEEE Std 1003.1-2004
     ("POSIX.1").

HISTORY
     The cksum utility appeared	in 4.4BSD.  md5	was added in NetBSD 1.3.  The
     functionality for md2, md4, sha1, and rmd160 was added in NetBSD 1.6.
     Support for the SHA-2 algorithms (SHA256, SHA384, and SHA512) was added
     in	NetBSD 3.0.  The functionality to verify checksum stored in a file
     (-c) first	appeared in NetBSD 4.0.	 Quiet mode (-q) was added in
     NetBSD 7.0.

FreeBSD	13.0			August 31, 2014			  FreeBSD 13.0

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | STANDARDS | HISTORY

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