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Ostiary prevents replay by salting. Client's reply is only valid for the unique salt that the server has generated and only for a short time and obviously only once.

A replay attack can only make the server do whatever the legit client intended it to do, just up to [timeout] seconds later.

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hmmm just validated my implementation

the deadline that is sent from the client is being added to the blocklist after the command was executed, so sending the same packet again will not work, because the deadline (which is in nanoseconds) is already on the blocklist and therefore the command will not be executed again.

This effectively means that replaying a packet is not possible, because the server will deny it.

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