A method comprising generating an updated security key upon expiration of a key exchange timer, transferring the updated security key to a Coaxial Network Unit (CNU), retaining an original key, wherein the updated security key comprises a different key identification number than the original key, accepting and decrypting upstream traffic that employs either the original key or the updated key, after transferring the updated security key to the CNU, creating a key switchover timer, before the key switchover timer expires, verify that upstream traffic transferred from the CNU on a logical link uses the updated security key, and when upstream traffic is encrypted using the updated security key, begin using the updated security key to encrypt downstream traffic and clear the key switchover timer.