3.1.6.12 SendBaseSymmetricKeyCache Cleanup Timer Event
When the SendBaseSymmetricKeyCache Cleanup Timer (section 3.1.2.12) expires, the protocol MUST apply the following logic, where CURRENT_TIME represents the current system time. This value is the number of seconds elapsed since midnight (00:00:00), January 1, 1970 (UTC) according to the system clock.
For each CachedSymmetricKey (section 3.1.1.3.3) ADM element instance rCachedSymmetricKey in the SendBaseSymmetricKeyCache ADM element, if rCachedSymmetricKey.CachedTime is less than CURRENT_TIME minus the value of the SymmetricKeyShortLifetime ADM element, the CachedSymmetricKey ADM element instance referenced by rCachedSymmetricKey MUST be deleted from the SendBaseSymmetricKeyCache ADM element.
If the SendBaseSymmetricKeyCache ADM element is not empty, the CachedSymmetricKey ADM element instance with the oldest CachedTime ADM attribute value MUST be found. The SendBaseSymmetricKeyCache Cleanup Timer MUST be restarted with a duration of the value of the SymmetricKeyShortLifetime ADM element plus one minute minus the difference between CURRENT_TIME and the oldest CachedTime ADM attribute value.