.\" $OpenBSD: skey.1,v 1.21 2000/11/09 17:52:38 aaron Exp $
.\"	@(#)skey.1	1.1 	10/28/93
.\"
.Dd October 28, 1993
.Dt SKEY 1
.Os
.Sh NAME
.Nm skey, otp-md4, otp-md5, otp-sha1, otp-rmd160
.Nd respond to an OTP challenge
.Sh SYNOPSIS
.Nm skey
.Op Fl x
.Oo
.Fl md4 | Fl md5 | Fl sha1 |
.Fl rmd160
.Oc
.Op Fl n Ar count
.Op Fl p Ar passwd
<sequence#>[/] key
.Sh DESCRIPTION
.Nm S/key
is a procedure for using one-time passwords to authenticate access to
computer systems.
It uses 64 bits of information transformed by the
MD4, MD5, SHA1, or RIPEMD-160 algorithms.
The user supplies the 64 bits
in the form of 6 English words that are generated by a secure computer.
This implementation of
.Nm s/key
is RFC 1938 compliant.
.Pp
When
.Nm skey
is invoked as
.Nm otp-method ,
.Nm skey
will use
.Ar method
as the hash function where
.Ar method
is currently one of md4, md5, sha1, or rmd160.
.Pp
If you misspell your password while running
.Nm skey ,
you will get a list of passwords
that will not work, and no indication of the problem.
.Pp
Password sequence numbers count backwards.
You can enter the passwords using small letters, even though
.Nm skey
prints them capitalized.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl n Ar count
Prints out
.Ar count
one-time passwords.
The default is to print one.
.It Fl p Ar password
Uses
.Ar password
as the secret password.
Use of this option is discouraged as
your secret password could be visible in a process listing.
.It Fl x
Causes output to be in hexadecimal instead of ASCII.
.It Fl md4
Selects MD4 as the hash algorithm.
.It Fl md5
Selects MD5 as the hash algorithm.
.It Fl sha1
Selects SHA-1 (NIST Secure Hash Algorithm Revision 1) as the hash algorithm.
.It Fl rmd160
Selects RMD-160 (160 bit Ripe Message Digest) as the hash algorithm.
.El
.Sh EXAMPLES
.sp 0
    % skey 99 th91334
.sp 0
    Enter secret password: <your secret password is entered here>
.sp 0
    OMEN US HORN OMIT BACK AHOY
.sp 0
    %
.Sh SEE ALSO
.Xr login 1 ,
.Xr skeyinfo 1 ,
.Xr skeyinit 1
.Pp
.Em RFC1938
.Sh TRADEMARKS AND PATENTS
S/Key is a Trademark of Bellcore.
.Sh AUTHORS
Phil Karn, Neil M. Haller, John S. Walden, Scott Chasin