I. Introduction
Recently, online social networks (OSNs) have exploded in popularity. The OSN providers, such as Facebook and Twitter, own vast amounts of personal data and information about relationships among their users. The data are often released to third parties for the purpose of studying social relationships, feeding advertisements to recommended target, and evaluating the effectiveness of applications. However, publishing OSNs without sufficient anonymization work results in privacy leakage, which causes concerns to the users of social media.