User's Manual

15
Possible configurations are:
Configuration Description
WebOTP Invisible The most widely used and best usable configuration. The authentication occurs in a totally
transparent way for the user.
WebOTP Alpha The configuration that best enables integrating with already existing password-based systems.
The authentication occurs by transmitting an alphabetical string which can be easily recognized
by already existing applications.
WebCHR This configuration enables using a bi-directional authentication for device multiple queries.
WebOTP Invisible
+ WebCHR
This configuration supports both protocols in the same device. With this configuration the device
exports two USB interfaces. With W
INDOWS
platforms the operating system requires more time
for recognizing the device, both during insertion and during removal. For guaranteeing
maximum usability it is advisable to use this configuration only when strictly necessary.
The details of the communication process are illustrated below in case it is necessary to integrate the WebOTP
authentication in an application. For operating with a web server just use the J
AVA
S
CRIPT
example provided in the
chapter Integration.
6.4.1 Invisible WebOTP Communication
The Invisible communication has been designed for hiding the authentication code transmission to the user and making
the process absolutely silent.
The transmission simulates pressing two special key combinations in order to represent the transmission of one bit at a
time. The two codes have been chosen in such a way as to not to have undesired effects in case they are intercepted by
generic applications and to guarantee maximum compatibility with all platforms.
The key combinations in use are as follows:
Keys Meaning
SHIFT+PAUSE
Representation of bit 0
NUM LOCK
Representation of bit 1
The actual codes of the keys received are different according to the execution context. Usually you only need to record
the pressing sequence of the single keys PAUSE and NUM LOCK which the standard keyboard codes correspond to.
Key Code Bit
PAUSE
19 0
NUM LOCK
144 1
Within a generic Windows application, if the codes are received via Windows WM_KEYDOWN messages, such codes
will be:
Key Character Code Bit
PAUSE
VK_PAUSE 0
NUM LOCK
VK_NUMLOCK 1
Within a generic J
AVA
S
CRIPT
, if the codes are received via the
onkeydown
event, such codes might differ according
to the operating system or the browser in use. However it is possible to have a univocal decoding by using the following
conversion:
Key Code Bit
PAUSE
19, 126 0
NUM LOCK
0, 12, 144 1
As the NUM LOCK key is used, during transmission the relevant keyboard led will blink.