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sha512hmac(8)            System Administrator's Manual           sha512hmac(8)



NAME
       sha512hmac - compute and check HMAC values


SYNOPSIS
       sha512hmac [OPTIONS] [-u | -k keyfile | -K key] [-c file [-q] | file [...] ]


DESCRIPTION
       The  sha512hmac  command  can compute and/or verify HMAC and unkeyed checksum values for the contents of files.
       Variations such as sha384hmac, sha256hmac, and sha1hmac all operate similarly except that  they  use  different
       digest algorithms.


SELF-TEST
       As  a  safety  measure, the tool will always attempt to verify a previously- computed HMAC over itself with the
       contents of a second file (sha512hmac.hmac for sha512hmac, and  a  similarly-named  file  for  each  variation)
       before processing any other files, and will exit with an error if the second file either cannot be read or does
       not match the computed value.


OPTIONS
       -c     Check that the HMAC values and names listed in the specified file(s) are correct for the files which are
              available.   The  format of the files should match the output which the tool produces when computing the
              values: a hex-encoded HMAC value and then a filename, separated by whitespace.

       -q     Suppress any output when checking values.

       -d cfgdir
              Specify the  configuration  directory  to  be  used  by  the  NSS  library.   The  default  location  is
              /etc/pki/nssdb.

       -h algorithm
              Generate  the  HMAC  value using a non-default hashing algorithm.  The default is determined by the name
              used to invoke the tool (sha1hmac, sha256hmac, etc.).  If no  default  can  be  derived  this  way,  the
              default  setting  will  be sha512.  Specify help or another invalid value to obtain a list of recognized
              algorithms.

       -u     Generate an unkeyed checksum instead of an HMAC.  The output produced by the tool should then be  compa-
              rable to that of sha1sum and related tools.

       -k filename
              Use  the  contents of the specified file as the secret key used in computing the HMAC values.  If no key
              file or text is specified, a hard-coded default value is used.  This option should always be used.

       -K text
              Use the text of the argument as the secret key used in computing the HMAC values.  If  no  key  file  or
              text is specified, a hard-coded default value is used.

       -b     Process file contents in binary mode, marking output as such by prefixing filenames with *.  This option
              is not expected to have any other meaningful effect.

       -t bits
              Truncate HMAC values to a given length when computing or verifying them.

       -S     Generate an HMAC over the tool itself and output it on standard out.  This  is  a  bootstrapping  option
              which is not expected to be used.

       -P     Attempt  to  pass  all input files through prelink -y before processing their contents.  The tool always
              attempts to do so when computing or performing a self-check.



EXAMPLES
       Example output from sha1hmac, for files on the developer's system:
         e64db5e8a9b8a40091e5302fa4de0bfc6c5d19d0  /etc/passwd
         e7d93a2c70ec4d7720c6f2b033c1e5ea19f2d677  /etc/group
         d732d6df77114ea6b81a43d64655f86b1e5ee925  /etc/services
         ad92162bef979054a75d1f3510e6b05902bec641  /etc/hosts


SEE ALSO
       fipshmac(1), fipscheck(1), prelink(8)


BUGS
       Probably, but let's  hope  not.   If  you  find  any,  please  either  report  them  in  the  bug  database  at
       http://bugzilla.redhat.com/  against  the  "hmaccalc"  component,  or  in  the trac instance at https://fedora-
       hosted.org/hmaccalc/.


AUTHOR
       Nalin Dahyabhai <nalinATredhat.com>



hmaccalc 0.9.12                   2009/03/19                     sha512hmac(8)