The much bigger issue is with hardware that doesn't have a local clock/battery. Critical initialization code should probably compare uptime with current epoch time if it needs a random seed for a long-use token.
> The much bigger issue is with hardware that doesn't have a local clock/battery.
Ummm, no. NTP normally runs on machines that have a local clock/battery, but which need an established network clock anyway.
> Critical initialization code should probably compare uptime with current epoch time if it needs a random seed for a long-use token.
Using time as a random seed is probably a mistake in the first place. You could perhaps try to add entropy from a clock, but you'd want another source of entropy. Generally crypto code needs network clocks for other things (think of Kerberos ticket expiration).
The average longevity of a Kerberos ticket makes it the perfect example for this attack vector, actually.
Are you familiar with something other than NTP as a time source for devices without CMOS? I have a project that desperately needs crypto without a clock.
