Abstract: A system and method of providing secure communications is provided. Messages are encrypted or decrypted in protected memory of a processor. Outbound messages from a secure network are prepared for encryption by adding a header outside of the protected memory and then encrypted in the protected memory. The encryption is performed by retrieving a key from a key cache as designated by rules in the header. The encrypted message is sent to the unsecure network. An inbound message from an unsecure network that is received in unprotected memory is sent to a decryption module in protected memory. The inbound message is decrypted using a key designated in its header and retrieved from the key cache. The decrypted message is returned to the unprotected memory, where it is stripped of the encryption header and then sent to its destination within the secure network.

Abstract: A method of retaining channel use by a secondary system is described. A secondary channel used during periods of normal communication between a secondary transmitter and receiver is split into sub-bands for use during a quiet period containing quiet phases. During the quiet period, while the transmitter communicates with the receiver on one sub-band, the receiver simultaneously senses for incumbent devices on another sub-band, as well as vice-versa. Transmission and sensing do not occur simultaneously on the same sub-band and transmission is limited to only one of the sub-bands. Transmission and sensing are performed by both the transmitter and the receiver on every sub-band over the course of the quiet period. The locations of secondary receivers are determined and employed during scheduling such that devices sufficiently separated from each other transmit during different quiet phases and transmit and sense in sub-bands separated by another sub-band.