SKEY(1) | General Commands Manual | SKEY(1)

# NAME

`skey`, `otp-md5`, `otp-rmd160`, `otp-sha1` — respond to an OTP challenge

# SYNOPSIS

`skey` | [`-x`] [`-md5` | `-rmd160` | `-sha1`] [`-n` count] [`-p` passphrase] ⟨sequence#⟩ [/] key

# DESCRIPTION

`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 2289 compliant.

Before using `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 used.

When `skey` is invoked as `otp-method`, `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 `skey` prints them capitalized.

The options are as follows:

`-md5` | `-rmd160` | `-sha1`
  Selects the hash algorithm: MD5, RMD-160 (160-bit Ripe Message Digest), or SHA1 (NIST Secure Hash Algorithm Revision 1).
`-n` count
  Prints out count one-time passwords. The default is to print one.
`-p` passphrase
  Uses passphrase as the secret passphrase. Use of this option is discouraged as your secret passphrase could be visible in a process listing.
`-x`
  Causes output to be in hexadecimal instead of ASCII.

# EXAMPLES

    $ skey 99 th91334
    Enter secret passphrase: <your secret passphrase is entered here>
    OMEN US HORN OMIT BACK AHOY
    $

# SEE ALSO

login(1), skeyaudit(1), skeyinfo(1), skeyinit(1), skey(5), skeyprune(8)

# STANDARDS

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.

# AUTHORS

Phil Karn
Neil M. Haller
John S. Walden
Scott Chasin

March 31, 2022 | Debian