Abstract: A secure communications system (100, FIG. 1) with a compromised communications node can quickly recover from the compromised condition by sending re-keying messages using a key encryption key hierarchy (200, FIG. 2). Each communications node (330, FIG. 3) includes a memory (300, FIG. 3) with a list of tier-group specific key encryption keys, and whenever a message arrives that is encrypted with a key encryption key in the list, the communications node decrypts the message. When the message includes a new traffic encryption key, the communications node has been re-keyed. Key encryption keys are managed hierarchically such that many communications nodes can be re-keyed with very few broadcast messages, thereby saving communications resources.

Abstract: The integrity of a remote communication unit (14) in a communication system is verified by comparing a hash value generated within the remote unit (14) to a hash value generated within a local unit (24). An interrogation message is generated within an interrogating entity (10) that includes a random seed value, memory range information identifying a memory range within the remote unit that is to be hashed, and position information identifying a position at which the random seed value is to be located within a data stream generated within the remote unit (14). The interrogation message is then delivered to the remote unit (14) which then performs a hashing operation based upon the parameters within the interrogation message to generate a hash value. The hash value is then returned to the interrogating entity (10) for comparison with a control value.

Abstract: Authorized intercepts of communications in a satellite communications system (10) are performed, according to which a law enforcement agency (LEA) can request the intercept of communications to and/or from subscriber units (SUs). In one embodiment, an LEA intercept request causes an intercept order for a particular target SU (420, FIG. 6) to be transmitted to one or more satellites (411-413, FIG. 6), where the intercept order is stored in an intercept table (410). Any communications traffic involving the target SU results in an intercept by a satellite, which routes a copy of the intercepted communications to the requesting LEA, either directly or via an associated intercept facility (426, FIG. 8).

Abstract: Authorized intercepts of communications in a communications system such as a satellite communications system (10) are controlled. Each law enforcement agency (LEA) can only intercept communications to subscriber units (SUs) within its jurisdiction. In addition, the identity of each authorized intercept target is known only to the requesting LEA. In one embodiment, a trusted entity, such as a network operations facility (NOF 22, FIG. 3), creates a list of ID's corresponding to all SUs within each LEA's jurisdiction. Each SU ID is provided both unencrypted and encrypted for one or more network nodes (NN 1-R, FIG. 3). A network intercept facility (IF 201, FIG. 3) selects a target SU ID, generates an intercept order encrypted for one or more NNs, and sends it to one or more NNs for execution.

Abstract: An single event upset (SEU) tolerant system for detecting and correcting an SEU includes a decision element (200) for receiving a plurality of outputs (120) from a plurality of signal generators (105) and producing an output (130) therefrom. The decision element includes voters which provide two levels of voting for the plurality of redundant outputs (120). First-level voters (300) provide intermediate voted outputs (315) which are received by a second-level voter to determine an output (130). An output disabler (400) determines when an output is provided external to the decision element. A plurality of comparators (210) receive intermediate voted outputs (315) from first-level voters and compare with a plurality of outputs from a plurality of signal generators to determine upset detected signals (125). An upset detected signal controls the selection of feedback for an element having experienced an SEU.