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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 pass- word 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 dis- tribution 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 com- pile-time configuration, but should be MD5. MD4 is compatible with the Bellcore S/Key Ver- sion 1 distribution. -f Force opiekey to continue, even where it nor- mally shouldn't. This is currently used to force opiekey to operate in even from termi- nals 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 back- wards 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 gener- ate the simple active attack protection. EXAMPLE wintermute$ opiekey -5 -n 5 495 wi01309 Using MD5 algorithm to compute response. Reminder: Don't use opiekey from telnet or dial-in sessions. Enter secret pass phrase: 491: HOST VET FOWL SEEK IOWA YAP 492: JOB ARTS WERE FEAT TILE IBIS 493: TRUE BRED JOEL USER HALT EBEN 494: HOOD WED MOLT PAN FED RUBY 495: SUB YAW BILE GLEE OWE NOR wintermute$


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.


ftpd(8), login(1), opie(4), opiepasswd(1), opieinfo(1), opiekeys(5), opieaccess(5), su(1)


Bellcore's S/Key was written by Phil Karn, Neil M. Haller, and John S. Walden of Bellcore. OPIE was cre- ated 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" mail- ing list. To join, send an email request to: skey-users-request@thumper.bellcore.com 7th Edition February 20, 1996 OPIEKEY(1)

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