RFID tag search is to find a particular tag in a group of tags by using a portable reader. Since a portable reader has own identifier and secret values associated with each tag, the portable reader can wirelessly communicate with the tag without help of central database. The RFID tag search can be useful to find a lost book among all RFID-tagged books in a library. However, the basic operation for RFID tag search has security and privacy problems. Secure search protocols to solve these problems were firstly discussed by Tan et al. Nonetheless, their protocols don't perfectly solve an illegal tag tracking problem by a reuse attack of a search query and also have an illegal reader tracking problem by revealing the portable reader ID over an insecure channel. In this paper, we propose strong authentication protocol for secure RFID tag search without help of central database which utilizes a block cipher (AES-128) and a timestamp. Our protocol can search a particular tag efficiently, and preserve user privacy against all major attacks.