Malicious attacks are not the only issue here. With individuals able to jam or spoof these signals, there is an increasing concern of the damage that could be caused by state-sponsored actors. The technology is now widely available that enables malicious actors to prevent GNSS data from getting through (jamming) or to trick a GNSS receiver into accepting fake data (spoofing). It has become much easier and cheaper to jam or spoof the radio signal GNSS uses to transmit time and location data. In recent years, GNSS has become increasingly vulnerable. This allows for good geographic coverage but comes with downsides that include: signal interference, unpredictable latency, outdated equipment and vulnerability to attack using signal jamming and spoofing. GNSS refers to a constellation of satellites with atomic clocks sending time and location data via radio signals to receivers on earth. Global Navigation Satellite Systems (GNSS) have been around since the 1970s and include a service familiar to most of us: the Global Positioning System (GPS). For any service where time is mission critical, some combination of these methods is advisable. Today time is distributed to digital networks in two main ways: via GNSS or over a network using fibre, copper or wireless. Let’s take a look at how time distribution works and the different methods for sending time from an accurate source (such as an atomic clock) to networked devices like your phone or laptop. In Sweden, the national time laboratory is run by RISE and the time is distributed by Netnod using a system of autonomous time nodes throughout the country. The national laboratories maintain their own local UTC and use a variety of methods for distributing this time nationally. TAI is then compared to UT1, a timescale based on the mean solar day, and the two together form the primary standard by which the world regulates clocks and time: Coordinated Universal Time (UTC). TAI is calculated using the weighted average time of 450 atomic clocks in 80 national laboratories worldwide. īy 1972, this led to the introduction of International Atomic Time (TAI). Atomic clocks were developed that used this property to measure time to an unprecedented level of accuracy. Instead of taking the earth’s rotation as a reference, the CGPM resolved a second should be defined using an extremely stable property of the caesium-133 atom where one of its resonance frequencies is precisely 9,192,631,770 times per second. But in 1967, a new way of defining a second was agreed upon at the 13th General Conference on Weights and Measures (CGPM). This gave a fairly stable frequency for calculating various gradations of time and meant that a second could be defined as 1/86,400 of the mean solar day i.e. Until the 1960s, the standard definitions of time were based on the regularity of the earth’s rotation. But what goes on behind the scenes here and what happens when things go wrong? Most of the digital tools that society relies on–across sectors such as finance, telecommunication, security and energy–only work with precise and reliable time synchronisation. In this post we will look at how network time works today and the technology that keeps it accurate and secure.
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