Database Reference
In-Depth Information
RFID tags in order to identify expired food. Clearly, the killing of
a tag at the point of sale would make this functionality useless.
Therefore, a number of methods have been proposed, which go beyond
the “kill” command for the purposes of providing privacy protection.
A slightly softer solution is to use a locking and unlocking mechanism
for the tags [75]. For example, the tags could be locked at the time of
check out in the store. The tags can then be unlocked with a meta-id
provided by the consumer, along with an associated PIN. This approach
has two primary disadvantages. One disadvantage is that the incorpo-
ration of smart technology makes the tag much more expensive. The
second disadvantage is that it is impractical for consumers to manage
meta-identifiers and PINs for all the different products that they may
buy.
5.2 Cryptographic Solutions
A possible solution is to encrypt the code in a tag before transmis-
sion. However, such a solution may not be very effective, because this
only protects the
content
of the tag, but not the ability to
uniquely iden-
tify
the tag. For example, the encoded tag is itself a kind of meta-tag,
which can be used for the purposes of tracking. Another solution is to
embed dynamic encryption ability within the tag. Such a solution, how-
ever, comes at a cost, because it requires the chip to have the ability
to perform such an encryption computation. Another solution which
has recently been proposed [40] is to perform the cryptographic com-
putations at the reader end itself, and store the resulting information
in the tags. This solution of course requires careful modification of the
reader-tag protocols. A number of cryptographic protocols for privacy
protection of library RFID activity are discussed in [55]. Some of the
cryptographic schemes [44, 48, 58] work with
re-writable
memory in the
tags in order to increase security. The tags are encrypted, and the reader
is able to decrypt them when they send them to the server, in order to
determine the unique meta-information in the tag. The reader also has
the capability to re-encrypt the tag with a different key and write it to
its memory, so that the (encrypted) tag signal for an eavesdropper is
different at different times. Such a scheme provides additional protec-
tion because of repeated change in the encrypted representation of the
tag, and prevents the eavesdropper from uniquely identifying the tag at
different times.
