opiekey, otp-md4, otp-md5 - Programs for computing responses to OTP challenges.

opiekey | otp-md4 | otp-md5 [-v] [-h] [-f] [-x] [-t type ] [-4|-5] [-a] [-n count ] sequence_number seed

opiekey takes the optional count of the number of responses to print along with a (maximum) sequence number and seed as command line args. It prompts for the user's secret pass phrase and produces an OPIE response as six words. If compiled to do so, it can prompt for the user's secret pass phrase twice to help reduce errors due to mistypes. The second password entry can be circumvented by entering only an end of line. opiekey is downward compatible with the key(1) program from the Bellcore S/Key Version 1 distribution and several of its variants.

-v

Display the version number and compile-time options, then exit.

-h

Display a brief help message and exit.

-4, -5

Selects MD4 or MD5, respectively, as the response generation algorithm. The default for otp-md4 is MD4 and the default for opie-md5 is MD5. The default for opiekey depends on compile-time configuration, but should be MD5. MD4 is compatible with the Bellcore S/Key Version 1 distribution.

-f

Force opiekey to continue, even where it normally shouldn't. This is currently used to force opiekey to operate in even from terminals it believes to be insecure. It can also allow users to disclose their secret pass phrases to attackers. Use of the -f flag may be disabled by compile-time option in your particular build of OPIE.

-a

Allows you to input an arbitrary secret pass phrase, instead of running checks against it. Arbitrary currently does not include '0' or 'n' characters. This can be used for backwards compatibility with key generators that do not check passwords.

-n <count>

the number of one time access passwords to print. The default is one.

-x

Output the OTPs as hexadecimal numbers instead of six words.

-t <type>

Generate an extended response of the specified type. Supported types are: word six-word hex hexadecimal init hexadecimal re-initialization init-word six-word re-initialization The re-initialization responses always generate the simple active attack protection.

opiekey(1) can lull a user into revealing his/her password when remotely logged in, thus defeating the purpose of OPIE. This is especially a problem with xterm. opiekey(1) implements simple checks to reduce the risk of a user making this mistake. Better checks are needed.

opie(4), opiepasswd(1), opieinfo(1), opiesu(1), opielogin(1), opieftpd(8), opiekeys(5), opieaccess(5), opiegen(1)

Bellcore's S/Key was written by Phil Karn, Neil M. Haller, and John S. Walden of Bellcore. OPIE was created at NRL by Randall Atkinson, Dan McDonald, and Craig Metz.

S/Key is a trademark of Bell Communications Research (Bellcore).

OPIE is discussed on the Bellcore "S/Key Users" mailing list. To join, send an email request to: skey-users-request@thumper.bellcore.com