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Description  |
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BACKGROUND OF THE INVENTION
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.
Another approach utilized by the prior an is the use of an individual's
"biometric" information. In particular, an individual's voice print can be
used to verify a person's identify. U.S. Pat. No. 4,876,717, issued to
Barron et al. on Oct. 24, 1989, describes a system that includes a PBX in
association with an adjunct processor. In this system, when a calling
party wants to access a computer system, the calling party first
establishes a "voice-call" to the system. Upon answering the voice-call,
the PBX transfers the call to the adjunct processor. The latter prompts
the calling party, via a voice recording, to speak a predefined
identifying phrase. As the calling party speaks this phrase the adjunct
processor generates a voiceprint of the calling party. After generating
the calling party's voiceprint, the calling party is instructed to
"hang-up." The adjunct processor than compares the calling party's
voiceprint to a set of voiceprints that represent authorized users. If
there is a match between the calling party's voiceprint and a voiceprint
of an authorized user, the adjunct processor calls back the calling party
to establish a data call between a host computer coupled to the PBX and
the calling party. In making this second telephone call, the adjunct
processor uses a telephone number that is a priori associated with the,
now identified, calling party.
The above-mentioned prior art, while providing secure arrangements to
access computers, arc not the complete answers to the problem. For
example, the Collins et al. and Archibald et al. approaches utilize the
calling party's ANI, but this does not guarantee the calling party is the
actual person authorized to use the computer system. It only guarantees,
to a degree, the location of the calling party in the public switched
telephone network. On the other hand, the Barron et al. patent, albeit
providing a better identification of the actual calling party, requires
two telephone calls, one to identify the calling party and one to
establish the data call upon verification of the calling party. In
addition, since this system initiates the data call using a predefined
telephone number, the original calling party must be at the location
associated with this predefined telephone number absent the use of any
sophisticated call forwarding arrangements. As a result, the two-call
approach is usually impractical for a person who is on a business trip.
SUMMARY OF THE INVENTION
We have realized a simple, and effective, technique for providing a
security arrangement that identifies a calling party to a computer system.
In particular, a multi-media modem couples both an analog channel and a
data channel to the computer system. The analog channel conveys the
calling party's identification information, while the data channel conveys
a data signal from the calling party. The computer system verifies the
calling party's identification information communicated over the analog
channel and, if the verification is successful, immediately establishes,
or continues, data communications with the calling party over the data
channel.
In an embodiment of the invention, a simultaneous voice and data modem
(SVD) is used to provide both an analog channel and data channel between a
calling party and a computer. The latter is coupled to both the analog
port and data port of the SVD modem. When the SVD modem answers an
incoming telephone call the SVD modem provides the calling party's voice
signal to the host computer via the analog port and a data signal to the
host computer via the data port. The computer then transmits a voice
recording to the calling party via the analog port This voice recording
instructs the calling party to speak a predefined phrase and to enter a
"login" via their data terminal. As the calling party speaks the phrase
the computer generates a voiceprint of the calling party. In addition,
after receiving the requested "login," the computer retrieves from a
nonvolatile memory device a voiceprint a priori associated with the
received "login." If there is a match between the calling party's
voiceprint and the retrieved voiceprint, the computer allows the data
connection to immediately be established or to continue. However, if the
calling party's voiceprint does not match, the computer hangs-up.
Advantageously, this technique uses only one telephone call and allows the
calling party to be located anywhere in the PSTN network since no
call-back is performed by the computer system.
BRIEF DESCRIPTION OF THE DRAWING
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;
FIG. 4 is an illustrative SVD symbol block that provides a secondary
communications channel;
FIG. 5 is an illustrative flow diagram of a method embodying the principles
of the invention for providing a security arrangement;
FIG. 6 is an illustrative flow diagram of another method embodying the
principles of the invention for providing a security arrangement;
FIG. 7 is an illustrative flow diagram of another method embodying the
principles of the invention for providing a security arrangement; and
FIG. 8 is an illustrative flow diagram of another method embodying the
principles of the invention.
DETAILED DESCRIPTION
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.
CPU 125, of SVD modem 100, controls switch 160, via line 126, as a function
of the above-mentioned operating mode of SVD modem 100. In the
"voice-only" mode, switch 160 couples any signal on line 162 to line 166
for transmission via telephone port 105, and couples any signal on line
149 to line 161 for transmission via PSTN port 110. The remaining
components, e.g., data encoder 155, data decoder 140, voice decoder 130,
and voice encoder 150, are disabled by control signals (not shown) from
CPU 125. Consequently, in the "voice-only" mode any analog signal
appearing at one of the analog ports is coupled, or bridged, to the other
analog port.
If SVD modem 100 is in the "data-only" mode, switch 160 couples any signal
on line 146 to line 161 for transmission via PSTN port 110, and couples
any signal on line 162 to line 131. In the "data-only" mode, voice encoder
150 and voice decoder 130 are disabled by control signals (not shown) from
CPU 125. In this mode of operation, any data signal appearing at DTE port
115 (assuming SVD modem 100 is not receiving "AT commands") is encoded by
data encoder 155. DTE port 115 is assumed to represent the above-mentioned
EIA RS-232 interface. The latter couples not only data from DTE 10 for
transmission to an opposite endpoint, but also couples commands from DTE
10 to SVD modem 100 during the well-known "AT command mode" of operation.
Data encoder 155 includes any of the well-known encoding techniques like
scrambling, trellis-coding, etc., to provide a sequence of symbols on line
156 at a symbol rate, 1/T to modulator 145. The symbols are selected from
a two-dimensional signal space (not shown). Note, since voice encoder 150
is disabled, adder 165 does not add a signal to the output signal from
data encoder 155. Modulator 145 illustratively provides a quadrature
amplitude modulated signal (QAM) to PSTN port 110 via switch 160.
Similarly in the reverse direction, a QAM signal received at PSTN port 110
is provided to demodulator 135 via switch 160. Demodulator 135 provides an
encoded data stream to data decoder 140. The latter performs the inverse
function of data encoder 155 and provides a received data signal to DTE
port 115 for transmission to DTE 10.
Finally, if SVD modem 100 is in the SVD mode, switch 160 couples any signal
on line 146 to line 161 for transmission via PSTN port 110, and couples
any signal on line 162 to line 131. In the SVD mode, voice encoder 150 and
voice decoder 130 are enabled by control signals (not shown) from CPU 125.
In this mode, any analog signal, e.g., a voice signal, appearing on line
149 is applied to voice encoder 150. The latter processes the voice signal
so that it is mapped into the two-dimensional signal space used by data
encoder 155 to provide a voice signal point. This voice signal point
defines the magnitude and angle of a "voice signal vector" about the
origin of the two-dimensional signal space. Voice encoder 150 provides a
sequence of two-dimensional signal points, at the predefined symbol rate
of 1/T symbols per sec., on line 151. Adder 165 adds each voice signal
vector on line 151, if any, to a respective one of the symbols provided by
data encoder 155 to provide a stream of signal points to modulator 145. As
described above, modulator 145 provides a QAM modulated signal to PSTN
port 110 via switch 160. This QAM modulated signal is the above-mentioned
SVD signal since it represents both voice and data.
In the reverse direction, the received SVD signal on line 131 is processed
as described above by demodulator 135 and data decoder 140 to provide the
received data signal on line 127. In addition, voice decoder 130 receives
both the received signal point sequence from demodulator 135 and the
decoded symbol sequence from data decoder 140. Voice decoder 130 includes
suitable buffering to allow for the decoding time needed by data decoder
140 to make a decision as to a received symbol. Voice decoder 130
subtracts the received symbol provided by data decoder 140 from the
respective received signal point provided by demodulator 135 to yield the
voice signal vector and then performs the inverse function of voice
encoder 150 to provide a received voice signal to telephone port 105, via
line 133.
As a result, this SVD technique advantageously provides a voice-band signal
that has both an audio portion and a data portion, hereafter referred to
as the analog channel and the data channel, respectively. This allows two
users, or endpoints, with simultaneous voice and data capable modems to
communicate data between them and talk at the same time--yet only requires
one "tip/ring" type telephone line at each user's location.
During the establishment of an SVD connection it is advantageous for the
calling SVD modem to initially signal the far-end, or called, SVD modem,
that the calling modem is also an SVD modem. This initial signaling is
accomplished by the use of an SVD identification signal that is
transmitted by the calling SVD modem after dialing the telephone number of
the called SVD modem. This type of notification allows the answering SVD
modem to immediately switch to an SVD mode as opposed to initially
defaulting to a standard data modulation like CCITT V.32 and then
switching to an SVD mode. An illustrative set of distinctive
identification signals for use by an SVD modem is shown in FIG. 3. These
hand-shaking signals include a calling signal, SVD CNG, which include
calling tones "a" and "b," and an answer identification signal, SVD AID,
which includes answering tones "a" and "b." The called SVD modem provides
the answer identification signal as an acknowledgment to the calling SVD
modem that the call has been answered by an SVD compatible modem.
The determination of what mode SVD modem 100 is in depends upon whether SVD
modem 1130 is originating or answering a telephone call. If SVD modem 100
is originating a telephone call, then the calling party, e.g., user 1, can
select the particular mode of operation in a number of ways. One
illustrative way is simply via a predefined command mode instruction
provided via DTE port 115. Another way is for SVD modem 100 to evaluate
the state of various signals at both telephone port 105 and DTE port 115.
For example, "voice-only" mode is entered if an "off-hook" signal is
detected at telephone port 105 and there is no "data-terminal-ready" (DTR)
signal from DTE 10 at DTE port 115. This DTR signal is a part of the
above-mentioned EIA RS-232 interface specification. Conversely,
"data-only" mode is entered if there is no "off-hook" signal but the DTR
signal is active. Finally, the SVD modem is entered if an "off-hook"
signal is detected and the DTR signal is active.
When user 1 is the called party, i.e., when SVD modem 100 answers an
incoming telephone call, the determination of what operating mode to enter
is performed as follows. SVD modem 100 first determines if an SVD
identification signal is being transmitted by the calling party's
equipment. If SVD modem 100 detects an SVD identification signal, then the
SVD mode of operation is entered. However, if no SVD identification signal
is detected, SVD modem 100 can either enter the "voice-only" mode or the
"data-only" mode. The particular selection is set by user 1 via a
predefined command mode instruction provided via DTE port 115. This
command mode instruction sets a "default" mode of operation for SVD modem
100 if no SVD identification signal is detected from the calling party's
equipment.
Once an opposite SVD modem has been identified and both modems are
communicating in the SVD mode, it is necessary for each SVD modem to
communicate control and status information to the opposite endpoint. This
is done via a secondary channel that communicates signaling information
between, e.g., SVD modem 100 and SVD modem 200, and can be implemented in
any number of ways. For example, as is known in the art, a secondary
channel can be provided by multiplexing the data modulated signal (here
the SVD signal) with another control signal; or a secondary channel can be
provided as described in the co-pending, commonly assigned, U.S. Patent
application of Bremer et al. entitled "Side-Channel Communications in
Simultaneous Voice and Data Transmission," issued on Apr. 9, 1996. FIG. 4
shows a diagram of a transmission scheme that includes a side-channel
within an SVD signal. This SVD side-channel not only provides for the
transport of additional information between any SVD endpoints--but also
allows the voice signal to be transmitted across the full bandwidth of the
SVD data connection. As can be observed from FIG. 4, information from an
SVD modem is provided in a frame, or "symbol block," e.g., symbol block
405. For the purposes of this example, a symbol block comprises 70
symbols. Consecutive symbols within each symbol block are identified as
S1, S2, S3, . . . , S70. Each symbol block is further divided into a data
segment, e.g., data segment 406; and a control segment, e.g., control
segment 407. Let the group of symbols in the data segment be S1 to S56.
These are the "data symbols" and always convey DTE data. For the purposes
of the following discussion the symbol rate is illustratively 3000
symbols/second (s/sec.), although other symbol rates may be used, e.g.,
2800 s/sec. At a symbol rate of 3000 s/sec., the average data symbol rate
of a symbol block is equal to (56/70).times.3000)=2400 s/sec.
Consequently, if there are 6 bits of data per data symbol, the resultant
data rate is 14400 bits/sec (bps). It is assumed that this data rate is
high enough to meet a user's needs so that the remaining bandwidth of the
SVD data connection can be allocated to the control segment, which
provides the side-channel.
The remaining symbols of the control segment, i.e., S57 to S70, are the
"control symbols." Usually, the latter never convey DTE data, but convey
control information. Each control symbol represents a number of "control
bits." For example, some of these control bits represent a state
identifier, which provides information to the far-end, or receiving, SVD
modem as to the mode of operation of the transmitting SVD modem, i.e.,
whether the transmitting SVD modem is in the "voice-only" mode,
"data-only" mode, or SVD mode, of operation. The control symbols are
encoded and scrambled the same as the DTE data symbols, e.g., they use the
same signal space. The control symbols provide the side-channel for
conveying additional signaling information between SVD modem endpoints.
Although the data symbols represent user data and the control symbols
represent control information, both the data and control symbols may also
convey analog data, which in this example is any voice signal that is
provided to SVD modem 100 by telephone 20. As a result, the side-channel
is a part of the simultaneous voice and data transmission.
Having described the general operation of an SVD modem, the inventive
concept will now be described. Referring back to FIG. 1, it is assumed
both SVD modems 100 and 200 have been preconfigured to default to the
above-mentioned SVD mode of operation. At this point, in order to
facilitate understanding of the inventive concept, reference can also be
made to FIG. 5, which represents an illustrative method embodying the
principles of the invention. In step 605, user 1 dials a telephone number
associated with computer 300. SVD modem 100 goes "off-hook" and transmits
this telephone number to PSTN 500 by providing a respective sequence of
dual-tone multifrequency (DTMF) digits. PSTN 500 routes this telephone
call as is known in the art. A local exchange carrier (not shown) within
PSTN 500 "rings" SVD modem 200 of computer 300 via line 301. In step 610,
SVD modem 200 answers the telephone call by going "off-hook" and, upon
detecting an SVD identification signal, performs a handshaking sequence
with SVD modem 100 to thereby establish a simultaneous voice and data
connection between computer 300 and the terminal equipment of user 1. SVD
modem 200 also "rings" voiceport 40 of computer 300 and provides a
"data-set-ready" (DSR) indication to DTE port 30. In response, computer
300 goes "off-hook" at voiceport 40 and provides a DTR indication to SVD
modem 200. As a result, the analog channel provided by SVD modem pair 100
and 200 communicates respective voice signals between voice port 40 of
computer 300 and telephone 20 of user 1, and the data channel between this
modem pair communicates respective data signals between DTE port 30 of
computer 300 and DTE 10 of user 1. It should be noted that although there
is "data communications" between user 1 and computer 300 at this point,
the latter has not yet allowed user 1 to access the information stored on
computer 300.
Computer 300 transmits a verification request to user 1 to provide
additional data information and a voice response in step 615. In
particular, computer 300 transmits a data prompt such as a "login" request
to user 1 over the data channel, and a prerecorded voice prompt, such as a
request to repeat a predefined phrase, over the voice channel. As noted
earlier, it is assumed that computer 300 includes standard speech
synthesis technology to provide the verbal prompt transmitted by computer
300. The predefined phrase can either be a "stock" phrase, or one of a
number of phrases randomly selected by the computer. User 1 transmits the
requested information in step 620 by entering, via DTE 10, a preassigned
"login," and by verbally repeating the requested phrase into a handset of
telephone 20. Computer 300 receives the requested data information via DTE
port 30 and records the vocal response of user 1 via voice port 40 to
create a voiceprint of user 1 in step 625. Computer 300 verifies both the
received data information and the voiceprint of user 1 in step 630. In
particular, computer 300 compares the data information entered by user 1
to a list of authorized logins stored in a nonvolatile storage device (not
shown) of computer 300. Similarly, computer 300 compares the voiceprint of
user 1 to an authorized voiceprint stored in a nonvolatile storage device
(not shown) of computer 300. This authorized voiceprint represents an
authorized user of computer 300 for that "login." If either, or both, of
the received data information and voiceprint do not match a respective
authorized login and authorized voiceprint, then computer 300 simply
disconnects in step 640. Computer 300 disconnects by "dropping" the DTR
signal via DTE port 30 and "hanging-up" at voice port 40. It should be
noted that if computer 300, for whatever reason, never creates a
voiceprint in step 625, e.g., user 1 does not repeat the requested phrase,
then computer 300 "times-out," e.g., after five seconds, and disconnects
from SVD modem 200 as described above.
However, if the both the data information entered by user 1 and the
voicepit of user 1 match a respective authorized login and voiceprint | | |
