NAME
x99token —
X9.9 software token
calculator
SYNOPSIS
x99token |
[-d] [-k
keyfile] [-n
count] |
x99token |
-i [-k
keyfile] |
DESCRIPTION
The x99token program is a simple X9.9
software token calculator. The token is initialized by using the
-i option. In this mode,
x99token requests a key. The key consists of 8 bytes
encoded in either hex or octal. When encoded in hex the key must consist of
16 hex digits, no spaces (e.g., "0123456789abcdef"). When encoded
in octal the key must consist of 8 3-digit octets, each separated by exactly
one space (e.g., "001 010 100 002 020 200 003 030"). Once the key
is entered, a PIN number is requested. The PIN number is used to perturb the
key before it is stored in a keyfile. This perturbation is not terribly
secure. You should assume that anyone with access to your keyfile will also
have access to your key.
When -i is not specified,
x99token is in calculator mode. In this mode you
must enter the same PIN as used in the initialization step. The PIN is used
to decode the key read from the keyfile. Next you enter the challenge you
have been presented with. The x99token program will
provide you with a response to the challenge. If the
-d option is used, the response will fold any hex
digits to decimal. If a count is specified by
-n, it indicates the number of challenges to
predict. The first challenge is always the entered challenge. By default the
value of count is 1, which implies only the entered
challenge is resolved.
Future challenges are predicted by the following algorithm:
- Encrypt the current challenge with the shared secret key
- AND each byte of the response with 0x0f
- Modulo each byte by 10 (0x0a)
- ADD 0x30 (ASCII value of '0') to each byte
The resulting 8 bytes are all ASCII decimal digits and are the predicted challenge. This process may be repeated.
FILES
- $HOME/.keyfile.des
- default keyfile
SEE ALSO
AUTHORS
Paul Borman ⟨prb@krystal.com⟩
CAVEATS
This is a very simple-minded program. The keyfile should be placed on a floppy disk which is kept physically secure.
Having not read the X9.9 standard, this may not be a complete or accurate implementation of the standard. This software is provided AS IS with no express or implied warranty.