RFC972

Network Working Group F. Wancho Request for Comments: 972 WSMR

                                                        January 1986

                  Password Generator Protocol

STATUS OF THIS MEMO

This RFC specifies a standard for the ARPA Internet community. Hosts on the ARPA Internet that choose to implement a Password Generator Protocol (PWDGEN) are expected to adopt and implement this standard. Distribution of this memo is unlimited.

BACKGROUND

Many security-conscious host administrators are becoming increasingly aware that user-selected login passwords are too easy to guess for even casual penetration attempts. Some sites have implemented dictionary lookup techniques in their password programs to prevent ordinary words from being used. Others have implemented some variant of a randomly generated password with mixed success. The problem arises from the fact that such passwords are difficult to remember because they cannot be pronounced or are based on a relatively short cycle pseudo-random number generator.

A version of the PWDGEN algorithm briefly described below has been in use for several years at a small number of sites in the Internet. Interest has recently been expressed at porting this algorithm to other sites. However, the relatively short cycle and the resulting randomness of the pseudo-random number generator available on these sites tends to interfere with the intended result of minimizing the potential duplication of passwords both within a site and across sites when a user has access to more than one site.

The PWDGEN Service described herein provides a means for sites to offer a list of possible passwords for the user to choose one from the first set, or optionally select from another set. With more than one site offering this service, it is then possible to randomly select which site to use and have multiple fallback sites should that site be unavailable.

Description

  The PWDGEN Service provides a set of six randomly generated
  eight-character CRLF-delimited "words" with a reasonable level of
  pronounceability, using a multi-level algorithm.  An
  implementation of the algorithm is available in FORTRAN-77 for
  examination and possible implementation by system administrators
  only.

Password Generator Protocol

  The uniqueness of the generated words is highly dependent on the
  randomness of the initial seed value used.  The availability of a
  single system-wide seed, updated after each access is highly
  desireable.  Seeds based on a time-of-day clock are unacceptable.
  Seed values should be stored as values in excess of 32 bits for
  best performance.

TCP Based PWDGEN Service

  One PWDGEN service is defined as a connection based application on
  TCP.  A server listens for TCP connections on TCP port 129.  Once
  a connection is established, the six CRLF-delimited words are
  generated and sent to the caller, and the connection is closed by
  the server. No dialog is used or required.

UDP Based PWDGEN Service

  Another possible PWDGEN service is defined as a datagram based
  application on UDP.  A server listens for UDP datagrams on UDP
  port 129.  When a datagram is received, the six CRLF-delimited
  words are sent back in an answering datagram.