TimeStream: Exploiting video streams for clock synchronization

Abstract

Network Time Protocol (NTP) is the most commonly used protocol for clock synchronization on the Internet.In the wake of frequent news about attacks that use Network Time Protocol (NTP), we propose a TimeStream algorithm, which – in its plain version (without any extra settings) – successfully synchronizes computer clocks up to seconds, by processing data found in video streams that use HTTP Live Streaming (also known as HLS) protocol. Further increase of precision is possible with a proper setup of the origin video servers.TimeStream provides secure time synchronization without requiring new ports, new hardware, or expensive cryptography, and uses information which – currently – is already making at least 70% of all Internet traffic.We observe that some intrinsic properties of video streaming over HTTP and congestion control of TCP yield some useful properties that facilitate good performance of the proposed method even in adverse network conditions. These make TimeStream to be robust against packet delay manipulation attack in which, an attacker adds specifically crafted delays to packets carrying time information.To the best of our knowledge, TimeStream may be one of the first methods of its kind that uses structure and core features of video streams and underlying network transportation protocol, to extract information about time and opens a new line of research on almost real-time extraction of useful information from video content.