NAME
skey —
respond to an OTP challenge
SYNOPSIS
skey |
[-n count]
[-p password]
[-t hash]
[-x] sequence# [/]
key |
DESCRIPTION
S/Key is a One Time Password (OTP) authentication system. It is intended to be used when the communication channel between a user and host is not secure (e.g. not encrypted or hardwired). Since each password is used only once, even if it is "seen" by a hostile third party, it cannot be used again to gain access to the host.S/Key uses 64 bits of information, transformed by the MD4 algorithm into 6 English words. The user supplies the words to authenticate himself to programs like login(1) or ftpd(8).
Example use of the S/Key program
skey:
% skey 99 th91334 Enter password: <your secret password is entered here> OMEN US HORN OMIT BACK AHOY %
The string that is given back by skey can
then be used to log into a system.
The programs that are part of the S/Key system are:
- skeyinit(1)
- used to set up your S/Key.
skey- used to get the one time password(s).
- skeyinfo(1)
- used to initialize the S/Key database for the specified user. It also tells the user what the next challenge will be.
- skeyaudit(1)
- used to inform users that they will soon have to rerun skeyinit(1).
When you run
skeyinit(1) you inform the system of your secret password. Running
skey then generates the one-time password(s), after
requiring your secret password. If however, you misspell your secret
password that you have given to
skeyinit(1) while running skey you will get a
list of passwords that will not work, and no indication about the
problem.
Password sequence numbers count backward from 99. You can enter
the passwords using small letters, even though skey
prints them capitalized.
The -n count
argument asks for count password sequences to be
printed out ending with the requested sequence number.
The hash algorithm is selected using the
-t hash option, possible
choices here are md4, md5 or sha1.
The -p password
allows the user to specify the S/Key password on the
command line.
To output the S/Key list in hexadecimal instead of words, use the
-x option.
EXAMPLES
Initialize generation of one time passwords:
host% skeyinit Password: <normal login password> [Adding username] Enter secret password: <new secret password> Again secret password: <new secret password again> ID username s/key is 99 host12345 Next login password: SOME SIX WORDS THAT WERE COMPUTED
Produce a list of one time passwords to take with to a conference:
host% skey -n 3 99 host12345 Enter secret password: <secret password as used with skeyinit> 97: NOSE FOOT RUSH FEAR GREY JUST 98: YAWN LEO DEED BIND WACK BRAE 99: SOME SIX WORDS THAT WERE COMPUTED
Logging in to a host where skey is
installed:
host% telnet host login: <username> Password [s/key 97 host12345]:
Note that the user can use either his/her S/Key
password at the prompt but also the normal one unless the
-s flag is given to
login(1).
SEE ALSO
TRADEMARKS AND PATENTS
S/Key is a trademark of Bellcore.
AUTHORS
Phil Karn
Neil M. Haller
John S. Walden
Scott Chasin