NAME

       Authen::Passphrase::Crypt16 - passphrases using Ultrix crypt16 algorithm

SYNOPSIS

               use Authen::Passphrase::Crypt16;

               $ppr = Authen::Passphrase::Crypt16->new(
                       salt_base64 => "qi",
                       hash_base64 => "8H8R7OM4xMUNMPuRAZxlY.");

               $ppr = Authen::Passphrase::Crypt16->new(
                       salt_random => 12,
                       passphrase => "passphrase");

               $salt = $ppr->salt;
               $salt_base64 = $ppr->salt_base64_2;
               $hash = $ppr->hash;
               $hash_base64 = $ppr->hash_base64;

               $ppr0 = $ppr->first_half;
               $ppr1 = $ppr->second_half;

               if($ppr->match($passphrase)) { ...

DESCRIPTION

       An object of this class encapsulates a passphrase hashed using the "crypt16" hash function found in
       Ultrix and Tru64.  Do not confuse this with the "bigcrypt" found on HP-UX, Digital Unix, and OSF/1 (for
       which see Authen::Passphrase::BigCrypt).  This is a subclass of Authen::Passphrase, and this document
       assumes that the reader is familiar with the documentation for that class.

       This is a derivation of the original DES-based crypt function found on all Unices (see
       Authen::Passphrase::DESCrypt).  The first eight bytes of the passphrase are used as a DES key to encrypt
       the all-bits-zero block through 20 rounds of (12-bit) salted DES.  (The standard crypt function does
       this, but with 25 encryption rounds instead of 20.)  Then the next eight bytes, or the null string if the
       passphrase is eight bytes or shorter, are used as a DES key to encrypt the all-bits-zero block through 5
       rounds of salted DES with the same salt.  The two eight-byte ciphertexts are concatenated to form the
       sixteen-byte hash.

       A password hash of this scheme is conventionally represented in ASCII as a 24-character string using a
       base 64 encoding.  The first two characters give the salt, the next eleven give the hash of the first
       half, and the last eleven give the hash of the second half.  A hash thus encoded is used as a crypt
       string, on those systems where the crypt16 algorithm is part of crypt(), but the syntax clashes with that
       of bigcrypt.  This module does not treat it as a crypt string syntax.

       Because the two halves of the passphrase are hashed separately, it is possible to manipulate (e.g.,
       crack) a half hash in isolation.  See Authen::Passphrase::DESCrypt for handling of a single half.

       Warning: This is a fatally flawed design, often providing less security than the plain DES scheme alone.
       Do not use seriously.

CONSTRUCTOR

       Authen::Passphrase::Crypt16->new(ATTR => VALUE, ...)
           Generates  a  new  passphrase  recogniser  object  using  the  crypt16 hash algorithm.  The following
           attributes may be given:

           salt
               The salt, as an integer in the range [0, 4096).

           salt_base64
               The salt, as a string of two base 64 digits.

           salt_random
               Causes salt to be generated randomly.  The value given for this attribute must be 12,  indicating
               generation  of  12  bits  of  salt.   The  source of randomness may be controlled by the facility
               described in Data::Entropy.

           hash
               The hash, as a string of 16 bytes.

           hash_base64
               The hash, as a string of 22 base 64 digits.

           passphrase
               A passphrase that will be accepted.

           The salt must be given, and either the hash or the passphrase.

METHODS

       $ppr->salt
           Returns the salt, as a Perl integer.

       $ppr->salt_base64_2
           Returns the salt, as a string of two base 64 digits.

       $ppr->hash
           Returns the hash value, as a string of 16 bytes.

       $ppr->hash_base64
           Returns the hash value, as a string of 22 base 64 digits.  This is the concatenation of the  base  64
           encodings of the two hashes, rather than a base64 encoding of the combined hash.

       $ppr->first_half
           Returns  the  hash of the first half of the passphrase, as an Authen::Passphrase::DESCrypt passphrase
           recogniser.

       $ppr->second_half
           Returns the hash of the second half of the passphrase, as an Authen::Passphrase::DESCrypt  passphrase
           recogniser.

       $ppr->match(PASSPHRASE)
           This method is part of the standard Authen::Passphrase interface.

SEE ALSO

       Authen::Passphrase, Authen::Passphrase::DESCrypt

AUTHOR

       Andrew Main (Zefram) <zefram@fysh.org>

COPYRIGHT

       Copyright (C) 2006, 2007, 2009, 2010, 2012 Andrew Main (Zefram) <zefram@fysh.org>

LICENSE

       This  module  is  free  software;  you  can redistribute it and/or modify it under the same terms as Perl
       itself.

perl v5.20.2                                       2015-06-07                   Authen::Passphrase::Crypt16(3pm)