Xavier Zhang is a physical security consultant and security researcher working with RFID enabled technologies and physical access control systems. He is the author of numerous pieces of documentation in Iceman’s proxmark3 repo such as the HID credential downgrade guide and an avid bug hunter in the proxmark3 community. Aside of physical security consulting, Xavier loves everything to do with DRM and reverse engineering how various forms of DRM are implemented in RFID tags. Currently Xavier is working on decoding the DRM used in a license violating closed source app based on the proxmark3 source, and all of the RFID tags it uses to help keep open source, open source.