.\" This file is in the PUBLIC DOMAIN.
.TH CRYPT 1 "2005-08-31"
.SH NAME
crypt \- create password hashes
.SH SYNOPSIS
crypt password [salt]
.SH DESCRIPTION
.B crypt
creates a hash from the supplied
.I password
and writes the hash to standard output, followed by a newline.  The hash is
generated by calling
.B crypt(3)
with the supplied
.I password
and
.I salt
as arguments.  If no
.I salt
is supplied,
.B crypt
will select a random two-character salt from the character set
.B [a-zA-Z0-9./]
(for the traditional DES algorithm).
.PP
The allowable salts are system-specific.
.B crypt(3)
should contain a list of the permissible values.
.PP
If called with no arguments,
.B crypt
emits a short help message to standard error and returns 1.
.SH "RETURN VALUE"
.B crypt
returns 0 upon success, or 1 if any error occurs.
.SH EXAMPLES
$ sudo grep '^mary:' /etc/shadow
.br
mary:pEcu81MYeYsDs:13000::::::
.PP
$ crypt littlelamb pE
.br
pEcu81MYeYsDs
.PP
$ crypt littlelamb '$1$eoChiw6i'
.br
$1$eoChiw6i$5MlhhEDPAWW4KA6gWNK6s/
.SH NOTES
.B pwgen(1)
makes an excellent MD5 hash algorithm salt generator.
.SH CAVEATS
A randomly chosen salt may not be cryptographically strong.  If this is a
concern, one should supply a salt instead.
.SH "SEE ALSO"
crypt(3), pwgen(1), http://wooledge.org/~greg/crypt/
.SH AUTHOR
Greg Wooledge <greg@wooledge.org>
.SH HISTORY
This manual describes version 0.1 of the software.