Synchronising clocks – devising a secure method 

Proposed by Dr Siddarth Joshi


We can build atomic clocks, super secure communication methods and GPS networks but being able to distribute a time synchronisation signal in a secure way remains a major challenge.

According to wired magazine a five-day disruption to the global navigation satellite systems which ensure we tell the time accurately, would cost the British economy an estimated £5.2 billion.

You can simply broad cast the time and then hope to account for propagation delays but then someone can just add an optical delay and fool this system.

You could think of multiple transmitters all triangulating a position such that this does not occur but the system can be thrown into confusion by the ‘evil entity’ just broadcasting their own time, or worse yet, modifying the signal you receive.


Can the team think of a secure way to synchronise clocks? Assume that there will be a signal to distribute (i.e. the ‘evil entity’ does not just cut the optical fibre, destroy your clocks etc.)

Output ideas

  1. Identifying the use cases for precise clock synchronisation will lead to some interesting and unexpected answers. Synchronisation to the pico second level is useful for a lot more than science experiments and will challenge your understanding of the world to find out more applications.
  2. Stating what the issues are with each method and why it should work or not is an interesting out come.
  3. Being able to list and categorise all possible attacks on the synchronising system.
  4. Calculations of how the synchronisation signal can be used to synchronise different types of clocks.
  5. Schematics of how they can correct for propagation time, relativistic effects and reference frames without compromising security.