Abstract: A call is connected between secure terminals (16) through a network (12). If a network address for the call is included on an approved list (46), a secure call setup procedure (54) is performed automatically. One terminal (16) automatically sends an auto-secure signal. If the other terminal detects the auto-secure signal, secure call setup procedure (54) is performed automatically. The secure call setup procedure (54) determines a current user-identity for the opposing party. If the current user-identity corresponds to a user-identity included on an approved list (76), an abbreviated secure call setup process (80) is performed. If the current user identity is not approved, a full secure call setup process (78) is performed. The abbreviated process (80) differs from the full process (78) in that it uses a traffic key obtained from a prior secure communication session and may be performed more quickly.

Abstract: A call is connected between secure terminals (16) through a network (12). If a network address for the call is included on an approved list (46), a secure call setup procedure (54) is performed automatically. One terminal (16) automatically sends an auto-secure signal. If the other terminal detects the auto-secure signal, secure call setup procedure (54) is performed automatically. The secure call setup procedure (54) determines a current user-identity for the opposing party. If the current user-identity corresponds to a user-identity included on an approved list (76), an abbreviated secure call setup process (80) is performed. If the current user identity is not approved, a full secure call setup process (78) is performed. The abbreviated process (80) differs from the full process (78) in that it uses a traffic key obtained from a prior secure communication session and may be performed more quickly.

Abstract: A call is connected between secure terminals (16) through a network (12). If a network address for the call is included on an approved list (46), a secure call setup procedure (54) is performed automatically. One terminal (16) automatically sends an auto-secure signal. If the other terminal detects the auto-secure signal, secure call setup procedure (54) is performed automatically. The secure call setup procedure (54) determines a current user-identity for the opposing party. If the current user-identity corresponds to a user-identity included on an approved list (76), an abbreviated secure call setup process (80) is performed. If the current user identity is not approved, a full secure call setup process (78) is performed. The abbreviated process (80) differs from the full process (78) in that it uses a traffic key obtained from a prior secure communication session and may be performed more quickly.

Abstract: An apparatus for secure communications contains a controller for automatically selecting one of several data ciphering devices utilizing one of a plurality of ciphering algorithms common to transmitting and receiving terminals. A transmitter for transmitting encrypted data, and a receiver for receiving encrypted data are coupled to the plurality of ciphering devices. The controller automatically determines which of the ciphering devices to employ for any given secure communication. The method for establishing a secure communications link includes the steps of exchanging a first message for determining a common key generation and ciphering method and comparing a further shared message for validation of communications terminal security.

Abstract: A method for passing supervisory control from a first station to a second station of a plurality of stations comprises steps of providing a message header in interstation messages in the first station, transmitting the interstation message from the first station to the second station, processing a message header from the interstation message to extract data and determining present identification of a system controller from the extracted data. The method includes steps of providing a first field containing message identification information, providing a second field containing supervisor station identification information, providing a third field containing update count information and providing a fourth field containing sending station identification information in the message header.

Abstract: An apparatus for secure communications contains a controller for automatically selecting one of several data ciphering devices utilizing one of a plurality of ciphering algorithms common to transmitting and receiving terminals. A transmitter for transmitting encrypted data, and a receiver for receiving encrypted data are coupled to the plurality of ciphering devices. The controller automatically determines which of the ciphering devices to employ for any given secure communication. The method for establishing a secure communications link includes the steps of exchanging a first message for determining a common key generation and ciphering method and comparing a further shared message for validation of communications terminal security.

Abstract: An apparatus for secure communications contains a controller for automatically selecting one of several data ciphering means utilizing one of a plurality of ciphering algorithms common to transmitting and receiving terminals. A transmitting means for transmitting encrypted data, and a receiving means for receiving encrypted data are coupled to the plurality of ciphering means. The control means automatically determines which of the ciphering means to employ for any given secure communication. The method for establishing a secure communications link includes the steps of exchanging a first message for determining a common key generation and ciphering method and comparing a further shared message for validation of communications terminal security.