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 SHASH(1)                           local                           SHASH(1)
                                 13 Feb 2000



 NAME
      shash - generates or checks digests or macs.

 SYNOPSIS
      shash [-nqvmdbtlhVL ] [-c file] [-a algorithm] [-i config_file] [-o keymode]
      [-k key] [ filename ... ]


 DESCRIPTION
      Shash is a program intended to produce message digests for files, or
      it can check with the output of a former run whether the message
      digests are still the same (i.e. whether the files changed). Shash
      uses several hash algorithms.  Since everyone can generate the message
      digest, it may not be suitable for some security related applications.

      Because of this shash also supports HMAC (rfc2104), which is a
      mechanism for message authentication using cryptographic hash
      functions.  So shash can use a key with a hash algorithm to produce
      hashes that can only be verified with the key. This way you can
      securely check (i.e. you are sure that nobody can modify the mac,
      without beeing detected) if files in a filesystem were altered.

      If the list of files and digests, that shash produces, is stored as a
      file in a disk, you should also create a digest of the list that holds
      the digests, to ensure that no file is removed from the list.

      If no filenames are given, it hashes the standard input to standard
      output.


 OPTIONS
      -m --hmac
           Works in hmac mode. Prompts for a password or accepts it from the
           --key parameter.

      -h --help
           Display a help screen and quit.

      -L --license
           Display the shash's license and quit.

      -V --verbose
           Display some extra information.

      --listkeygen
           Lists all the supported key generation algorithms. (The
           algorithms that generate a key from a password)

      -o --keymode keymode
           Keymode may be one of the modes listed when the --listkeygen
           parameter is specified.



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 SHASH(1)                           local                           SHASH(1)
                                 13 Feb 2000



      -q --quiet
           Suppress some not critical warnings.

      -b   Use binary mode. In unix environment, only difference between
           this and the normal mode is an asterix preceding the filename in
           the output.

      -c   Check the checksum of all files listed in file against the
           checksum listed in the same file.

      -t, --text
           Treat all input files as text files.  This is the reverse option
           to --binary.

      -n, --nolock
           It does not use fcntl() to lock the files.

      -d, --doublecheck
           It prompts twice for the password.

      --nosalt
           It does not use a salt, which is normally combined with the key
           in HMAC mode.

      -k --key KEY
           Enter the keyword via the command line. The KEY is then used as
           keyword instead of prompting for it. Keep in mind that someone
           may see the command you are executing and so your key.

      -c --config FILE
           Use the specified configuration file. The default is .shashrc in
           your home directory. The format of the configuration file is the
           same as the parameters. An example file is:
            algorithm sha1
            keymode s2k_simple
            key a_very_secret_one


      -a --algorithm ALGORITHM
           The algorithm used to encrypt and decrypt. Unless the bare flag
           is specified there is no need to specify these for decryption.

      -l --list
           Displays the supported algorithms.

      -v --version
           Version. Display the version number and quit.


 ENVIRONMENT
      Shash uses the following environment variables:



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 SHASH(1)                           local                           SHASH(1)
                                 13 Feb 2000



      SHASH_KEY: to specify the key.

      SHASH_KEYMODE; to specify the keymode.

      You can use these instead of using the command line (which is
      insecure).

 SEE ALSO
      md5sum(1)

 DIAGNOSTICS
      Exit status is normally 0;

      Usage: shash [-nqvmdbtlhVL] [-c file] [-a algorithm] [-i config_file]
      [-o keymode] [-k key] [filename...]


 AUTHORS
      Copyright (C) 1999 Nikos Mavroyanopoulos (nmav@hellug.gr).



































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