md5 man page on OpenBSD

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MD5(1)			   OpenBSD Reference Manual			MD5(1)

NAME
     md5 - calculate a message-digest fingerprint (checksum) for a file

SYNOPSIS
     md5 [-bpqrtx] [-c [checklist ...]] [-s string] [file ...]

DESCRIPTION
     md5 takes as input a message of arbitrary length and produces as output a
     128-bit "fingerprint" or "message digest" of the input.  It was
     conjectured that it would be computationally infeasible to produce two
     messages having the same message digest (a collision), or to produce any
     message having a given prespecified target message digest.	 However,
     collisions have now been produced for MD5, so the use of other message
     digest functions, such as sha256(1), is now preferred.

     The MD5 algorithm is intended for digital signature applications, where a
     large file must be "compressed" in a secure manner before being encrypted
     with a private (secret) key under a public-key cryptosystem such as RSA.

     The options are as follows:

     -b	     Output checksums in base64 notation, not hexadecimal.

     -c [checklist ...]
	     Compares all checksums contained in the file checklist with newly
	     computed checksums for the corresponding files.  Output consists
	     of the digest used, the file name, and an OK or FAILED for the
	     result of the comparison.	This will validate any of the
	     supported checksums (see cksum(1)).  If no file is given, stdin
	     is used.

     -p	     Echoes stdin to stdout and appends the MD5 sum to stdout.

     -q	     Only print the checksum (quiet mode).

     -r	     Reverse the format of the hash algorithm output, making it match
	     the output format used by cksum(1).

     -s string
	     Prints a checksum of the given string.

     -t	     Runs a built-in time trial.  Specifying -t multiple times results
	     in the number of rounds being multiplied by 10 for each
	     additional flag.

     -x	     Runs a built-in test script.

     The MD5 sum of each file listed on the command line is printed after the
     options are processed.

EXIT STATUS
     The md5 utility exits 0 on success, and >0 if an error occurs.

SEE ALSO
     cksum(1), sha1(1), sha256(1)

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

CAVEATS
     Since collisions have been found for MD5, the use of sha256(1) is
     recommended instead.

OpenBSD 4.9		       September 3, 2010		   OpenBSD 4.9
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