Authentication

SDLS anti-replay interdicts replay on the space link and SDLS-protected crosslinks, but the technique also covers internal-bus replay (SpaceWire, MIL-STD-1553) outside SDLS scope, so it governs the link portion.

SDLS anti-replay, monotonic sequence numbering bound under the frame MAC, rejects a re-sent telecommand whose counter is below the receiver's high-water mark; the adversary cannot refresh the counter without the key, so the replayed command is interdicted.

SDLS anti-replay rejects the replayed commands that trigger a data dump, but the technique's dominant scope is the downlink capture itself, which is owned by encryption, so authentication addresses only the enabling trigger.

SDLS crosslink authentication limits which peers a vehicle trusts, but a compromised neighbor holding valid keys produces authentic frames SDLS cannot reject, so it governs the trust boundary without interdicting the compromised-peer vector.

SDLS authentication rejects forged command frames from an unkeyed rogue transmitter, but this umbrella technique also spans jamming, relay of legitimately-keyed traffic, and other foothold vectors SDLS does not interdict, so it governs the command-injection sub-vector.

A rogue ground station transmitting mission-compatible signals cannot produce a valid frame MAC without the shared keys, so its telecommands fail SDLS authentication and are rejected, interdicting unauthorized commanding over the space-ground link.

Where a crosslink runs SDLS, a rogue spacecraft without valid keys has its frames rejected; but coverage is conditional on SDLS being present on the crosslink and does not stop the proximity, RF-geometry, and relay vectors, so it governs rather than fully interdicts.

SDLS authentication rejects forged crosslink messages that merely appear to come from a trusted neighbor, but lateral movement through a genuinely compromised, validly-keyed vehicle is not stopped, so it governs rather than interdicts.