Method for dial-in access security using a multimedia modem

#The present invention relates to data communications equipment and to computer systems. In particular, this invention relates to the use of data communications equipment to provide secure access to a computer system.

#The use of computers in today's world is continually on the increase, from main-frames to personal computers more and more people are using computer systems. In fact, it is the accessibility of a computer itself, via a modem and the public switched telephone network (PSTN), that allows almost anyone to benefit from the use of a computer. Unfortunately, this "dial-up" accessibility also seems to attract "intruders," i.e., illegitimate users of a computer system. As a result, the security of a computer system, or even a network of computers, as to both the integrity and distribution of the information stored on a computer is an item of continuing concern to the legitimate owners and operators of computers. In response to this need of prodding some type of access security to a computer system a number of alternatives have been proposed.

#Some approaches utilize the well-known "automatic number identification" (ANI) feature available from most public switched telephone network providers. For example, U.S. Pat. No. 5,003,595, issued to Collins et al. on Mar. 26, 1991, describes a system where a private branch exchange (PBX), upon answering an incoming data call, provides the calling party's ANI to an adjunct processor, i.e., computer, for analysis. This adjunct processor compares the calling party's ANI to a list of authorized ANI numbers. If the calling party's ANI is on this authorization list then the data call is completed. However, if the calling party's ANI is not on the list of numbers, the adjunct processor instructs the PBX not to answer the data call. In contrast to the Collins et al. patent, U.S. Pat. No. 5,301,246, issued Apr. 5, 1994 to Archibald et al. describes a modem that includes a list of authorized ANI numbers. For any incoming data call the modem compares the calling party's ANI to each of the authorized ANI numbers. The modem answers the incoming data call only if a match is found.

#FIG. 1 shows a block diagram of a simultaneous voice and data communications system embodying the principles of the invention;

#FIG. 2 shows a block diagram of a simultaneous voice and data modem;

#FIG. 3 is a table showing illustrative SVD identification signal assignments;

#A block diagram of a simultaneous voice and data communications system embodying the principles of the invention is shown in FIG. 1. As shown in FIG. 1, there are illustratively two communications endpoints represented by user 1 and computer 300. Other than the inventive concept, which is described below, computer 300 is any commercially available computer system that includes at least one data terminal equipment (DTE) port, DTE 30, and at least one analog port, herein represented by voice port 40. It is assumed the computer 300 includes components (not shown) that allow computer 300 to both generate prerecorded messages via voice port 40 and generate voiceprints from incoming voice signals received at voice port 40 as known in the art. Both voice port 40 and DTE port 30 of Computer 300 are coupled to PSTN 500 via SVD modem 200. The equipment of user 1 includes DTE 10, telephone 20, and SVD modem 100. DTE 10 is coupled to SVD modem 100 via line 11. Telephone 20 is coupled to SVD modem 100 via line 21. It is assumed that line 21 represents a "tip/ring" type of electrical interface. SVD modem 100 is coupled to public switched telephone network (PSTN) 500, via local loop 101, for originating and answering telephone calls. Local loop 101 is a typical "tip/ring" facility, i.e., a wire-pair, upon which a voice-band signal is transmitted between SVD modem 100 and PSTN 500. Finally, the signal connections between the data communications equipment, represented by SVD modems 100 and 200, and respective data terminal equipment, represented by DTEs 10 and 30, are assumed to conform to the Electronic Industry Association (EIA) RS-232 interface.

#Before describing the inventive concept below, a description of the general operation of an SVD modem is provided using SVD modem 100 as an example. The basic operation of an SVD modem is also described in the commonly assigned, U.S. Pat. No. 5,448,555 of Bremer et al. entitled "Simultaneous Analog and Digital Communication," issued on Sep. 5, 1995.

#FIG. 2 shows an illustrative block diagram of SVD modem 100. SVD modem 100 operates in either a "voice-only" mode, a "data-only" mode, or an SVD mode. In the "voice-only" mode, SVD modem 100 simply communicates a signal, e.g., a voice signal, present on telephone port 105 to PSTN port 110. In the "data-only" mode, SVD modem 100 modulates a data signal received via DTE port 115 for transmission via PSTN port 110 to a remote data endpoint, and demodulates a modulated data signal received via PSTN port 110 for transmission to DTE 10. Finally, in the SVD mode, SVD modem 100 provides the combination of the "voice-only" and "data-only" mode with the exception that the signal received and transmitted via PSTN port 110 is a combined voice and data signal (hereafter referred to as an "SVD signal"). Other than the inventive concept, the individual components of SVD modem 100 are well-known and are not described in detail. For example, CPU 125 is a microprocessor-based central processing unit, memory, and associated circuitry for controlling SVD modem 100.