.TH PASSWD 1
.SH NAME
passwd, netkey, iam \- change user password
.SH SYNOPSIS
.B passwd
[
.I username\fR[@\fPdomain\fR]\fP
]
.PP
.B netkey
.PP
.B auth/iam
[
.I username
]
.SH DESCRIPTION
.I Passwd
changes the invoker's Plan 9 password and/or APOP secret.
The Plan 9 password is used to login to a terminal while
the APOP secret is used for a number of external services:
POP3, IMAP, and VPN access.  The optional argument specifies
the user name and authentication domain to use if different
than the one associated with the machine
.I passwd
is run on.
.PP
The program first prompts for the old Plan 9 password in the specified
domain to establish
identity.
It then prompts for changes to the password and the
secret.
New passwords and secrets must be typed twice, to forestall mistakes.
New passwords must be sufficiently hard to guess.
They may be of any length greater than seven characters.
.PP
.I Netkey
uses the password to encrypt network challenges.
It is a substitute for a SecureNet box.
.PP
These commands may be run only on a terminal, to avoid
transmitting clear text passwords over the network.
.PP
.I Auth/iam
can be run only by the the host owner (the user specified as the contents of
.BR /dev/hostower ).
With it both the identity and password of the host owner may
be changed.  For example, if start a terminal and log in as
.LR tor ,
you may later change identity to
.LR supertor .
If the host owner changes, all processes running as the host owner
also change their identity to the new user id.
.PP
Without an argument, 
.I Auth/iam
just sets the password of the host owner.
This can be used on machines like the Bitsy which have no
possibility of user input until the bootstrap procedure has already
started a number of processes.
.SH FILES
.B /dev/key
.SH SOURCE
.B /sys/src/cmd/auth/passwd.c
.br
.B /sys/src/cmd/auth/netkey.c
.SH "SEE ALSO"
.IR encrypt (2),
.IR cons (3),
.IR securenet (8)
.PP
Robert Morris and Ken Thompson,
``UNIX Password Security,''
.I AT&T Bell Laboratories Technical Journal
Vol 63 (1984), pp. 1649-1672