Authen::DecHpwd - DEC VMS password hashing

       The  original  C  implementation  of  "LGI$HPWD"  was written by Shawn Clifford.  The code has since been
       developed by Davide Casale, Mario Ambrogetti, Terence Lee, Jean-loup Gailly, Solar Designer,  and  Andrew
       Main (Zefram).

       Mike  McCauley  <mikem@open.com.au> created the first version of "Authen::DecHpwd", establishing the Perl
       interface.  This was based on Shawn Clifford's code without the later developments.

       Andrew Main (Zefram) <zefram@fysh.org> created a new "Authen::DecHpwd" based on the more developed C code
       presently used, and added ancillary functions.

       Copyright (C) 2002 Jean-loup Gailly <http://gailly.net>

       Based in part on code from John the Ripper, Copyright (C) 1996-2002 Solar Designer

       Copyright (C) 2006, 2007, 2009, 2010, 2011, 2017 Andrew Main (Zefram) <zefram@fysh.org>

       This module implements the "SYS$HASH_PASSWORD" password hashing function from VMS (also known as
       "LGI$HPWD"), and some associated VMS username and password handling functions.

       The password hashing function is implemented in XS, with a hideously slow pure Perl backup version for
       systems that can't handle XS.

       UAI_C_AD_II
       UAI_C_PURDY
       UAI_C_PURDY_V
       UAI_C_PURDY_S
           These  constants are used to identify the four password hashing algorithms used by VMS.  They are the
           "UAI$C_" constants in VMS.

           "UAI_C_AD_II" refers to a 32-bit  CRC  algorithm.   The  CRC  polynomial  used  is  the  IEEE  CRC-32
           polynomial,  as  used  in Ethernet, and in this context is known as "AUTODIN-II".  The hash is merely
           the CRC of the password.

           "UAI_C_PURDY", "UAI_C_PURDY_V", and "UAI_C_PURDY_S" refer to successive refinements of  an  algorithm
           based  on  Purdy  polynomials.  All of these algorithms use the salt and username parameters as salt,
           use the whole password, and return an eight-byte (64-bit) hash.  The main part of the algorithm,  the
           Purdy  polynomial,  is  identical  in all three.  They differ in the pre-hashing, particularly in the
           treatment of the username parameter.

           In "UAI_C_PURDY" the username is truncated or space-padded to 12 characters before being  hashed  in.
           "UAI_C_PURDY_V"  accepts  a  variable-length  username.   "UAI_C_PURDY_S"  accepts  a variable-length
           username and also includes the password length in the hash.  "UAI_C_PURDY_S" also does some extra bit
           rotations when hashing in the username and password strings, in order to avoid aliasing.

       lgi_hpwd(USERNAME, PASSWORD, ALGORITHM, SALT)
           This is the "SYS$HASH_PASSWORD" function from VMS (also known as "LGI$HPWD"), but with the parameters
           in a different order.  It hashes the PASSWORD string in a manner determined by the other  parameters,
           and returns the hash as a string of bytes.

           ALGORITHM  determines  which  hashing  algorithm  will  be  used.  It must be the value of one of the
           algorithm constants supplied by this module (see above).

           SALT must be an integer in the range [0, 2^16).  It modifies the hashing so that  the  same  password
           does not always produce the same hash.

           USERNAME  is  a  string that is used as more salt.  In VMS it is the username of the account to which
           the password controls access.

           VMS usernames and passwords are constrained in character set and length,  and  are  case-insensitive.
           This function does not enforce these restrictions, nor perform canonicalisation.  If restrictions and
           canonicalisation  are desired then they must be applied separately.  The functions "vms_username" and
           "vms_password" described below may be useful.

       vms_username(USERNAME)
           Checks whether the USERNAME string matches VMS username syntax, and canonicalises it.   VMS  username
           syntax  is  1  to 31 characters from case-insensitive alphanumerics, "_", and "$".  If the string has
           correct username syntax then the username is returned in canonical form (uppercase).  If  the  string
           is not a username then "undef" is returned.

       vms_password(PASSWORD)
           Checks whether the PASSWORD string is an acceptable VMS password, and canonicalises it.  VMS password
           syntax  is 1 to 32 characters from case-insensitive alphanumerics, "_", and "$".  If the string is an
           acceptable password then the password is returned in canonical form (uppercase).  If  the  string  is
           not an acceptable password then "undef" is returned.

       This module is free software; you can redistribute it and/or modify it under the terms of the GNU General
       Public License as published by the Free Software Foundation; either version 2 of the License, or (at your
       option) any later version.

perl v5.40.0                                       2024-10-20                               Authen::DecHpwd(3pm)

       Authen::DecHpwd - DEC VMS password hashing

       VMS::User

               use Authen::DecHpwd qw(
                       UAI_C_AD_II UAI_C_PURDY UAI_C_PURDY_V UAI_C_PURDY_S
                       lgi_hpwd
               );

               $hash = lgi_hpwd("JRANDOM", "PASSWORD", UAI_C_PURDY_S, 1234);

               use Authen::DecHpwd qw(vms_username vms_password);

               $username = vms_username($username);
               $password = vms_password($password);