Why do you use a smartcard? - Smartcard Security
Because it is a secure storage and a secure computation device.
So it is a good place to hide secrets.
- Physical protection - It is hard to open a smartcard and access
data in it. It is not impossible, but is much harder than
tampering workstations and PCs.
- Restricted API - A smartcard exports a minimal set of interfaces
to avoid exporting flawed interfaces that lead to vulnerabilities.
- Mobility - A user can carry a smartcard, physically separating it
from the outside world.