— respond to an OTP
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 MD5, RIPEMD-160, or SHA1 algorithms. The user
supplies the 64 bits in the form of 6 English words that are generated by a
secure computer. This implementation of
S/Key is RFC
skey, the system needs to be
initialized using skeyinit(1); this will establish a secret passphrase. After
that, one-time passwords can be generated using
skey, which will prompt for the secret passphrase.
After a one-time password has been used to log in, it can no longer be
skey is invoked as
skey will use
method as the hash function where
method is currently one of md5, rmd160, or sha1.
If you misspell your secret passphrase while running
skey, you will get a list of one-time passwords that
will not work, and no indication of the problem.
Password sequence numbers count backwards. You can enter the
passwords using small letters, even though
prints them capitalized.
The options are as follows:
- Selects the hash algorithm: MD5, RMD-160 (160-bit Ripe Message Digest), or SHA1 (NIST Secure Hash Algorithm Revision 1).
- Prints out count one-time passwords. The default is to print one.
- Uses passphrase as the secret passphrase. Use of this option is discouraged as your secret passphrase could be visible in a process listing.
- Causes output to be in hexadecimal instead of ASCII.
$ skey 99 th91334 Enter secret passphrase: <your secret passphrase is entered here> OMEN US HORN OMIT BACK AHOY $
login(1), skeyaudit(1), skeyinfo(1), skeyinit(1), skey(5), skeyprune(8)
N. Haller, C. Metz, P. Nesser, and M. Straw, A One-Time Password System, RFC 2289, February 1998.
TRADEMARKS AND PATENTS
S/Key is a Trademark of Bellcore.
Neil M. Haller
John S. Walden