NAME

       ykchalresp - Perform challenge-response operation with YubiKey

SYNOPSIS

       ykchalresp [-nkey] [-1 | -2] [-H | -Y] [-N] [-x] [-v] [-6 | -8] [-t] [-iFILE] [-V] [-h]

DESCRIPTION

       Send a challenge to a YubiKey, and read the response. The YubiKey can be configured with
       two different C/R modes — the standard one is a 160 bits HMAC-SHA1, and the other is a
       YubiKey OTP mimicking mode, meaning two subsequent calls with the same challenge will
       result in different responses.

OPTIONS

       -nkey
           send the challenge to the nth key found.

       -1
           send the challenge to slot 1. This is the default

       -2
           send the challenge to slot 2.

       -H
           send a 64 byte HMAC challenge. This is the default.

       -Y
           send a 6 byte Yubico OTP challenge.

       -N
           non-blocking mode — abort if the YubiKey is configured to require a key press before
           sending the response.

       -x
           challenge is hex encoded.

       -v
           enable verbose mode.

       -6
           output the response in OATH format, 6 digits.

       -8
           output the response in OATH format, 8 digits.

       -t
           use current time as challenge instead of reading challenge from command line (as in
           default TOTP mode, seconds since 1970-01-01 00:00:00 / 30 encoded as an 8 byte
           challenge).

       -iFILE
           take challenge from FILE instead of as an argument. If file is - challenge is read
           from STDIN

       -V
           print tool version and exit.

EXAMPLE

       The YubiKey challenge-response operation can be demonstrated using the NIST PUB 198 A.2
       test vector.

       First, program a YubiKey with the test vector :

           $ ykpersonalize -2 -ochal-resp -ochal-hmac -ohmac-lt64 -a303132333435363738393a3b3c3d3e3f40414243
            ...
           Commit? (y/n) [n]: y
           $

       Now, send the NIST test challenge to the YubiKey and verify the result matches the
       expected :

           $ ykchalresp -2 'Sample #2'
           0922d3405faa3d194f82a45830737d5cc6c75d24
           $

BUGS

       Report ykchalresp bugs in the issue tracker
       https://github.com/Yubico/yubikey-personalization/issues

SEE ALSO

       The ykpersonalize home page https://developers.yubico.com/yubikey-personalization/

       YubiKeys can be obtained from Yubico http://www.yubico.com/