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A comment on Planned GPS outages in southern California. Parent comment

Re:Planned GPS outages in southern California by revelation on Tuesday June 07, 2016 @03:09PM (#11856929)
There is a separate encrypted GPS signal, which used to have better precision as the public signals had intentional noise added to them.

Of course, GPS is a rather old system and I'm unclear how you would add encryption in a way that it's not compromised when someone gets access to a decoder but also doesn't endanger "mission success" because a encryption key punch card is missing and the drone refuses to start. It's like the nuclear launch codes being all zeroes.

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Re:Planned GPS outages in southern California by tjohns on Tuesday June 07, 2016 @04:12PM (#11857412)
As I understand it, encrypted GPS (L2) does depend on key material being periodically loaded from a fill device for proper operation.

The keys are rotated periodically, so if somebody stole a decoder, it would only work until the key in memory expires. (Military GPS receivers also have a "zeroize" button to destroy the keys in case of imminent capture.)

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