Traditional access control cards are read-only, playback devices.
When read, they simply send a fixed sequence, much like a bar
code. With the right equipment, one may record the sequence and
play it back. Traditional access control readers may fail under
Proximity smart card systems were designed to contain accounts
and sensitive information. They have means to authenticate cards
and readers, and they effectively detect and resist playback attacks.
Traditional access control cards will gladly spill their contents to
any compatible reader. Just pass a card by and it will gladly reveal
the entire content of that card.
Proximity smart card systems resolve this problem by sharing
secret keys. Without these keys, other readers can't access the
cards and other cards can't access the readers. They may be
compatible but without the shared keys, they won't reveal their
secrets. Modern, secure, micro-controller based readers allow you to
change keys, which gives you final control over your readers and