Anonymous and secure time stamping across optical fibre owing to a new invention

A new invention makes it possible to guarantee anonymity and security in time comparisons across optical fibre. The invention was granted a Swedish patent in the autumn of 2011 and has received a great deal of international attention.

An increasing number of services and transactions take place electronically across the world between, for example, states, companies, stock exchanges and individuals. This imposes greater demands on the time stamping of transactions to be correct and robust. In some applications there is also a need for anonymity in the time transfer.

The most robust method is currently time and frequency transfer through optical fibre. However similar to all other technologies where there is a need for a high level of precision, this method is based on symmetrical two-way communication of signals. Both the sender and recipient must then confirm the signals in order to compensate for time delays in order to enable time stamping. This restricts the possibility of anonymous time transfers.

The research group within time and frequency at SP Measurement Technology has now found a solution for this problem. By sending two one-way signals with different wave lengths through the fibre and measuring the difference in the arrival time between the two signals, SP has illustrated that it is possible to calculate the time change in the fibre. With the aid of SP's calculation algorithm, the difference measurement and the calculation of the delay can be made for the recipient. Owing to this the time comparison can be made without the recipients disclosing their identity.

The concept is now also being further developed by the US Naval Observatory, which among other things is responsible for the time-keeping in the American navigation system, GPS.

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