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by woodruffw 2627 days ago
> As it’s just a replay attack of the original signal, encryption can’t help.

Couldn't this be mitigated by added a nonce or using CBC within the cryptosystem? Replay attacks are well understood; I'd be surprised if any (eventual) proposal for signed/encrypted GPS didn't include something to defend against them.
1 comments
jhayward 2627 days ago
As I loosely explained in another comment, you essentially never see repeats. The replay happens at the speed of light, and time stamps are broadcast once every 6 seconds at 50 BPS.

The receiver sees the rebroadcast because it captures the receiver's RF chain by being the strongest signal.

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