Sorry just saw this reply. Absolutely agreed that downgrade attacks are a real problem, though TPMs can easily mitigate this by using their monotonic counter f

Sorry just saw this reply. Absolutely agreed that downgrade attacks are a real problem, though TPMs can easily mitigate this by using their monotonic counter functions. Still, secure time is useful for many things. There are a lot of network protocol approaches to secure time, but for applications where it really matters where you cannot trust GPS, atomic clock PCI cards are in the low thousands of dollars now.