sha256 man page on FreeBSD

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MD5(1)			  BSD General Commands Manual			MD5(1)

     md5, sha1, sha256, rmd160 — calculate a message-digest fingerprint
     (checksum) for a file

     md5 [-pqrtx] [-s string] [file ...]
     sha1 [-pqrtx] [-s string] [file ...]
     sha256 [-pqrtx] [-s string] [file ...]
     rmd160 [-pqrtx] [-s string] [file ...]

     The md5, sha1, sha256 and rmd160 utilities take as input a message of
     arbitrary length and produce as output a “fingerprint” or “message
     digest” of the input.  It is conjectured that it is computationally
     infeasible to produce two messages having the same message digest, or to
     produce any message having a given prespecified target message digest.
     The MD5, SHA-1, SHA-256 and RIPEMD-160 algorithms are intended for digi‐
     tal 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.

     MD5 has been completely broken as far as finding collisions is concerned,
     and should not be relied upon to produce unique outputs.  This also means
     that MD5 should not be used as part of a cryptographic signature scheme.
     At the current time (2009-01-06) there is no publicly known method to
     “reverse” MD5, i.e., to find an input given a hash value.

     SHA-1 currently (2009-01-06) has no known collisions, but an attack has
     been found which is faster than a brute-force search, placing the secu‐
     rity of SHA-1 in doubt.

     It is recommended that all new applications use SHA-256 instead of one of
     the other hash functions.

     The following options may be used in any combination and must precede any
     files named on the command line.  The hexadecimal checksum of each file
     listed on the command line is printed after the options are processed.

     -s string
	     Print a checksum of the given string.

     -p	     Echo stdin to stdout and append the checksum to stdout.

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

     -r	     Reverses the format of the output.	 This helps with visual diffs.
	     Does nothing when combined with the -ptx options.

     -t	     Run a built-in time trial.

     -x	     Run a built-in test script.

     The md5, sha1, sha256 and rmd160 utilities exit 0 on success, and 1 if at
     least one of the input files could not be read.

     cksum(1), md5(3), ripemd(3), sha(3), sha256(3)

     R. Rivest, The MD5 Message-Digest Algorithm, RFC1321.

     J. Burrows, The Secure Hash Standard, FIPS PUB 180-2.

     D. Eastlake and P. Jones, US Secure Hash Algorithm 1, RFC 3174.

     RIPEMD-160 is part of the ISO draft standard "ISO/IEC DIS 10118-3" on
     dedicated hash functions.

     Secure Hash Standard (SHS):

     The RIPEMD-160 page:

     This program is placed in the public domain for free general use by RSA
     Data Security.

     Support for SHA-1 and RIPEMD-160 has been added by Oliver Eikemeier

BSD			       September 7, 2008			   BSD

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