User's Manual
25
The devices are calibrated in the production phase with an error lower than 2 ppm (parts per million). The storage
temperature can increase the error though, as regards the period of exposure to such a temperature.
The progress of the error according to the temperature is expressed in the following table.
T [C°] E [ppm]
-10 -42
-5 -31
0 -21
5 -14
10 -8
15 -3
20 -1
25 0
30 -1
35 -3
40 -8
45 -14
50 -21
55 -31
60 -42
In proportion with the temperature variation the induced error always tends to slow down the clock. It is therefore
advisable to use an asymmetric input window.
For instance, storing the device for 10 hours at the temperature of 60° C brings about an error accumulation of 1.5
seconds.
Ε
= 10 * 3600 [seconds] * 42 / 1000000 = 1.5 [seconds]
7.6 Error management
All SDK functions return an error code which indicates whether the operations has been completed successfully or not.
The generic error codes that are common to all functions are:
Error code Description
SUCCESS The operation has been completed successfully.
INVALID_ARGUMENT One of the past arguments is invalid.
INVALID_STATE It is not possible to carry out the operation requested in the current state.
During the authentication process further errors are possible suggesting the type of error incurred, the cause and the
possible remedy.
Typically after one of such errors it is advisable to always allow the user to attempt authentication again in order to
prevent Denial Of Service – type attacks aiming at blocking the rightful users. Given the security characteristics of the
WebOTP and WebCHR protocol, brute force attacks are not effective and there is no reason for blocking the rightful
user.
Error code Description
SUCCESS The operation has been completed successfully.
The user is authenticated.
TIME_OVERFLOW The time information used in the authentication process has undergone an
unexpected lead backward.
In that case it is important to check that the time source used on the server is
working properly.
-80
-70
-60
-50
-40
-30
-20
-10
0
-20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70
T [C°]
Errore [ppm]