Abstract: A secure facsimile interface includes a main CPU (30) having associated therewith a bulk memory (32) for storing transfer data between a Group 3 facsimile machine (20) and a secure encryptor/decryptor telephone unit (10) that operates in accordance with MIL-STD-188-161. The main CPU (30) interfaces with the Group 3 machine (20) through an RJ11 port. A TELCO simulator (42) generates the telephone signals necessary to communicate with the Group 3 machine (20) and a FAX interface (36) is operable to interface between the audio and digital domain, and with the main CPU (30). An RS232 interface is connected to the encryptor/decryptor telephone unit (10) with a bit stream processor (40) operable to interface with the protocol thereof.