  In this paper, the privacy of two recent RFID tag ownership transfer
protocols are investigated against the tag owners as adversaries. The first
protocol called ROTIV is a scheme which provides a privacy-preserving ownership
transfer by using an HMAC-based authentication with public key encryption.
However, our passive attack on this protocol shows that any legitimate owner
which has been the owner of a specific tag is able to trace it either in the
past or in the future. Tracing the tag is also possible via an active attack
for any adversary who is able to tamper the tag and extract its information.
The second protocol called, Chen et al.'s protocol, is an ownership transfer
protocol for passive RFID tags which conforms EPC Class1 Generation2 standard.
Our attack on this protocol shows that the previous owners of a particular tag
are able to trace it in future. Furthermore, they are able even to obtain the
tag's secret information at any time in the future which makes them capable of
impersonating the tag.
