Indian Statistical Institute
XCB is a Tweakable Enciphering Scheme (TES) which was first proposed in 2004. The scheme was modified in 2007. The authors call these two versions of XCB as XCBv1 and XCBv2 respectively. XCBv2 was later proposed as a standard for encryption of sector oriented storage media in IEEE-std 1619.2 2010. There is no known proof of security for XCBv1 but the authors provided a concrete security bound for XCBv2 and a \"Proof\" for justifying the bound. In this paper they show that XCBv2 is not secure as a TES by showing an easy distinguishing attack on it.