Insufficient Authentication in Legacy Ground-Link Telemetry Handshake

AstroSec's ground-link telemetry module supports a legacy compatibility mode for older mission hardware that predates our current handshake protocol. During a scheduled protocol audit, we identified that this legacy fallback accepted a weaker authentication path than the primary handshake under a narrow condition: when the primary handshake failed due to a clock-skew mismatch rather than an authentication failure specifically.

In practice, this meant a ground station experiencing significant clock drift — rather than an actual malicious actor — was the far more common trigger, but the fallback path's weaker authentication meant we couldn't rule out a deliberately induced clock-skew condition being used to force the weaker path.

No client mission was affected in a way we could confirm as exploitation; this was identified proactively through our own protocol audit process, not a client-reported incident. The fix makes legacy compatibility mode an explicit opt-in per ground station (rather than an automatic fallback), and every legacy-mode handshake is now logged and surfaced to mission operators, so any future use of the weaker path is visible rather than silent.

Missions still running hardware that requires legacy compatibility mode should coordinate with their AftPak mission-assurance contact to review whether opt-in legacy mode is still necessary for their ground segment.