Abstract: An unattended apparatus and method for isolating and relaying secure communications under adverse circumstances without awareness of encryption keys uses known and/or inferred characteristics of received transmissions to identify, isolate, and retransmit only friendly communications without decryption or re-encryption, and in embodiments also without awareness of applicable TRANSEC algorithms and keys. A channelizer digitizes energy received within a bandwidth of interest, which is then analyzed to detect chip timing, identify and demodulate pulses, and assemble secure messages for retransmission. In embodiments, the retransmissions use the original frequencies and TRANSEC parameters, and/or otherwise adhere to applicable TRANSEC and MSEC constraints so that the relayed messages are accepted by intended recipients. Embodiments provide interoperability with existing secure communications such as Link 16 and CDL.