In 2007, choi et al.’s has proposed a ownership transfer mechanism [3]. We find that the privacy of customers cannot be guaranteed in their scheme. Therefore, we propose a new design to overcome the privacy problem. Our ownership transfer mechanism is not only used in transaction but also extended for post-sale service. Our proposal contributes a practical protocol that meets all important issues: anonymity, secure ownership transfer, tag’s access control, tag’s untraceability, simplicity.