An important parameter to determine for TESLA is the key disclosure delay . A short disclosure delay will cause packets to violate the security condition and cause packet drop, while a long disclosure delay causes a long authentication delay. Note that although the choice of the disclosure delay does not affect the security of the system, it is an important performance factor. We describe a new method on how to choose a good disclosure delay . In particular, we show as follows that if RTT is a reasonable upper bound on the round trip time between the receiver and the sender, then in case of using direct time synchronization, we can choose , where is the interval duration. In case of indirect time synchronization, we can choose , where is the sum of both the sender and receiver time synchronization error, and is a reasonable upper bound on the network delay of a packet traveling from the sender to the receiver.
Consider a packet that is constructed using the MAC key in time interval which will be disclosed time intervals later. The packet arrives at the receiver at its local time . Hence the security condition is that
where is the beginning time of the th time interval and is the time interval duration. Assume packet was sent at the sender's local time . Hence . We denote the average network delay time from the sender to the receiver with and the average network delay time from the receiver to the sender is , and henceIn case of a direct time synchronization, using the same notation as in section 3.3, , and hence we can derive at the end that a tight bound for to satisfy the equation 1 is , which allows most of packets to satisfy the security condition and still the receiver would not need to wait much extra longer than necessary to authenticate the packets. Similarly in case of an indirect time synchronization, we can derive that a good is