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BACKGROUND OF THE INVENTION
The present invention relates to a system (method and apparatus) for
retrieving secure information from a mass storage medium such as a CD-ROM,
for temporary storage and usage by an information user.
Systems for storage and retrieval of secure information are well known in
the art. As used herein, the term "secure information" is intended to mean
information (alphanumeric data, graphics and the like) which is either
encrypted or otherwise protected to prevent access thereto except by an
authorized user. Such systems have been proposed and are employed both for
the case where the information source (database) is centralized, and for
the case where the information source has been distributed to multiple
users. In the latter case, CD-ROMs have been used to export databases to
multiple users so that information storage and retrieval takes place at
the user site.
In the U.S. Pat. No. 5,010,571 to Ron Katznelson and the U.S. Pat. Nos.
4,827,508, 4,977,594 and 5,050,213 to Victor Shear, it is proposed to
provide encrypted digital information on CD-ROMs at the user site and to
monitor and account for each item or "packet" of information which is
retrieved and decrypted from a CD-ROM by an authorized user.
This concept of retrieving information on a "pay-as-you-go" basis is also
disclosed in the U.S. Pat. No. 5,247,575 of Peter J. Sprague and Thomas H.
Lipscomb to include individual access to encrypted data which is
"broadcast" to multiple user sites from a central source and/or to provide
individual access to encrypted data stored at a central source, using
conventional time sharing techniques and transmission via telephone
dial-up or local area network (LAN) or wide area network (WAN)
communication.
All of these prior art systems permit the user's access to the secure
information to be monitored and strictly controlled. This is accomplished,
in practice, by maintaining a record at each user site of each information
packet which is retrieved and the cost thereof to the user, and then
"polling" all user sites from a remote central site, on a regular basis,
to retrieve the user data and, if necessary, disable the equipment at one
or more user sites to prevent further access to the secure information at
these sites.
Systems of this type require specialized electronic circuitry at each user
site which operates in cooperation with a central computer at a remote
site. Particularly when decryption must be effected at each user site, it
is difficult to maintain the security and integrity of this electronic
equipment.
Furthermore, the provision of an electronic circuit board, or the like, to
a personal computer at a user workstation can (actually or apparently)
compromise the integrity of this computer, thus making the system
difficult to implement in practice.
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide a method and
apparatus for retrieving secure information from a mass storage medium at
a user site which is not susceptible to attack or compromise by a user.
It is a further object of the present invention to provide a system for
retrieving secure information from a mass storage medium at a user site
which does not require a reconfiguration of a personal computer at the
user site.
These objects, as well as further objects which will become apparent from
the discussion that follows, are achieved, in accordance with the present
invention, by providing a personal computer or "host computer" and a mass
storage medium reader arranged on an SCSI bus, and providing a "decryption
controller", in a separate enclosure outside of the host computer and also
arranged on the SCSI bus, which is addressable by the host computer as if
it were the storage medium reader. Upon receipt of an information request,
the decryption controller initiates a request to the storage medium reader
for the desired information, retrieves this information, decrypts it if it
is encrypted, and then passes it to the host computer. The decryption
controller is thus "transparent" to the host computer.
For a full understanding of the present invention, reference should now be
made to the following detailed description of the preferred embodiments of
the invention as illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a representative diagram of a workstation comprising a personal
computer (PC), a CD-ROM reader and a decryption controller all arranged on
an SCSI bus.
FIG. 2 is a block diagram of a decryption controller for use in the system
of FIG. 1.
FIG. 3 is a flow chart showing the general operation of the decryption
controller of FIG. 2.
FIG. 4 is a flow chart showing the general operation of the decryption
controller of FIG. 2 in response to an SCSI command from the host
computer.
FIG. 5 is a flow chart showing the general operation of the decryption
controller in response to an SCSI command to retrieve an item of
information.
FIG. 6 is a flow chart showing the operation of the decryption controller
in decrypting data.
FIG. 7 is a flow chart showing the operation of the decryption controller
in creating a decryption key.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The preferred embodiments of the present invention will now be described
with reference to FIGS. 1-7 of the drawings. Identical elements in the
various figures are designated with the same reference numerals.
FIG. 1 illustrates the general nature of the system according to the
present invention. As shown here, the system involves a digital computer
workstation which is capable of retrieving secure data from a database
stored on one or more CD-ROMs.
In order to prevent unauthorized access to the stored information, at least
some of the individual items of information ("information packets") are
encrypted prior to storage on a CD-ROM. Some of the information packets
may also be stored in decrypted (cleartext) form on a CD-ROM and can be
retrieved by any workstation user by means of a CD-ROM reader. However,
only an authorized user with a proper validated code is allowed to decrypt
the encrypted information packets.
Upon release of the secure and, if desired, the non-secure information to
an authorized user, the user is charged a preset fee set by the
information provider (copyright owner or publisher of the information).
This charge is effected automatically by debiting a financial account
which has previously been established between the user and the information
provider.
To implement this system, there is provided a workstation comprising a
personal computer (PC) 10, a CD-ROM reader 12 and a decryption controller
14. These three devices, which may be stand-alone devices each arranged in
a separate enclosure or combined in one or two enclosures--e.g., the PC 10
in one enclosure and the CD-ROM reader 12 and controller 14 in another
--are connected in a well-known manner to a Small Computer System
Interface ("SCSI") bus 16 via a bus interface and controller 18.
The personal computer 10 and the CD-ROM reader 12 are conventional devices
which are available commercially. The decryption controller is a special
purpose device which operates to receive encrypted data from the CD-ROM
reader, decrypt this data if authorized to do so, and transport the
decrypted data to the host computer 10 for storage either in its active
memory (RAM) or hard disk drive.
The decryption controller also keeps a running account of the identity of,
and charge for each information packet which is decrypted for later
transmission, e.g. by telephone line, to a central billing facility at a
remote site. A monitoring facility of this type is known from the
aforementioned U.S. Pat. Nos. 5,010,571; 4,827,5089 and 5,247,575.
Once an information packet is decrypted and transferred to the host
computer 10, the workstation user can display it on the computer screen,
print out a hard copy and/or transmit a copy by LAN or modem to another
workstation.
In accordance with the SCSI standard, the SCSI bus extends no more than
twenty-six feet in length from end to end and is provided with terminating
impedances at each end. Each unit arranged on the bus is provided with a
unique address from a maximum of eight addresses (zero to seven). The
computer is usually given the address number seven; the addresses of the
other devices on the bus may be selected from zero to seven with a manual
switch arranged on each device.
In the preferred embodiment of the present invention, the decryption
controller 14 is disposed in its own enclosure, separate and apart from
the personal computer 10 and possibly also the CD-ROM reader 12. To
safeguard the firmware and codes which are used by the electronic
circuitry, the decryption controller may be provided with light-sensitive,
erasable memory circuits so that the contents of memory are erased if and
when the enclosure is opened.
FIG. 2 shows a preferred embodiment of the decryption controller. This
device is connected to the SCSI bus 16 via receptacles 20 and a fifty pin
header 22. The SCSI bus controller 18 operates in conjunction with a CPU
24 to receive requests for data from the host computer 10 and initiate
requests for this data from the CD-ROM reader 12.
The device is provided with its own separate power supply 26 so that it
operates completely independently of the host computer 10.
The decryption controller is also provided with a 2400 baud modem and
telephone interface 28 so that it may communicate with a central billing
computer at a remote site. This central billing computer routinely calls
the decryption controller 18 at regular intervals--for example, each
night--to download the logged information concerning each information
packet (IP) that was decrypted, and/or to credit the financial account
maintained by the decryption controller when the workstation user makes
payment.
The decryption controller 18 can also communicate with other devices, such
as printers or the like, by means of an RS-232C transceiver 30 and an
associated serial port connector 32.
The SCSI address is set from zero to six by a manual ID selector 34. Date
and time are provided by a real time clock 36.
Firmware for the decryption controller is provided on two 128K flash memory
chips 38; intermediate scratch pad storage is provided by a 256K dynamic
RAM 40.
Decryption of encrypted data is effected by a Data Encryption Standard
(DES) module 42 which operates in conjunction with a key code scrambler
44. The key code scrambler maintains the keys used by the DES module for
decryption. Alternatively, the decryption function and/or the key code
scrambler function may be implemented in software (firmware) operating in
the CPU 24.
All keys utilized by the system are created and maintained in the
decryption controller so that neither the workstation user nor the PC 10
will have access to these keys.
All of the electronic circuit devices contained in the decryption
controller of FIG. 2 are standard, commercially available devices. Part
numbers are shown in FIG. 2 for the major components.
In a preferred embodiment of the invention, the system of FIG. 1 and, in
particular, the decryption controller of FIG. 2, operates in the manner
shown by the flow charts of FIG. 3-7.
When first switched on, the CPU 24 executes a self-test routine as is
conventional in the art (Block 45 in FIG. 3). Error messages are
communicated to the host computer via the SCSI bus for display to the
system user. Thereafter, the CPU enters the idle mode (Block 46) and
awaits an interrupt.
If the decryption controller receives an SCSI command from the host
computer (Block 47) it processes this command (Block 48) as will be
described hereinafter in connection with FIG. 4. If the decryption
controller receives an incoming telephone message (Block 49) from a
central billing computer, it processes this message (Block 50) before
proceeding. Typical telephone messages are set forth in Table I:
TABLE I
Set Credit (in financial account)
Set Item Price
Set User Password
Clear Financial Account to Zero
Get Financial Account Information
Get User Information
Create User Information
Remove User Information
Send User a Message
Similarly, if an RS232 connection is established (Block 51), permitting
communication either to or from the decryption controller, the controller
either transmits information, for example to a printer, or receives a
serial message of the type noted above. In this case, the serial message
is processed (Block 52) and the controller returns to the idle state.
FIG. 4 illustrates how an SCSI command from the host computer is treated by
the decryption controller. When an SCSI command is received (Block 53) it
is analyzed and processed (Block 54) by the decryption controller. Typical
SCSI commands are set forth in Table II:
TABLE II
Get Financial Account Information
Get Purchased Item Information
Assent/Don't Assent to Purchase Item
Log In
Log Out
Poll for an Asynchronous Event (such as an "on sale" notice) Set User's
Default Billing Reference (e.g., last
billing reference number used)
Purchase Item
Get Decryption Controller Status (i.e., error codes)
Get User Information (i.e., currently logged-in user)
Receive Decrypted Data
Certain PC commands require the decryption controller to call the central
billing computer via the telephone modem. For example, if the financial
account is decremented to zero, the decryption controller will
automatically call and request additional credit. In this case, the
decryption controller makes the call (Block 55) and executes the call-out
sequence (Block 56). In the call-out protocol, the decryption controller
dials the number of the central billing facility and transmits both its
telephone and identification (ID) numbers. This simple transmission
requests an immediate call-back from the central computer during which the
financial account is automatically updated.
Each telephone transaction, initiated by the central billing computer,
preferably comprises three steps:
(1) A download to the central billing facility of the current financial
account status, all billing transactions completed since the previous
download, and the user information stored in the decryption controller;
(2) A transmission from the central billing facility to the decryption
controller of any updates, such as changes in pricing information and the
like; and
(3) A communication of all error codes from the decryption controller to
the central billing facility which indicate that the decryption controller
is not functioning properly.
In addition, the financial account balance in the decryption controller can
be updated by the central billing facility. It can be credited, if payment
was made to the central billing facility by the user, or debited, for
example if a check was returned from the bank marked "insufficient funds".
Each billing transaction provided to the central billing facility
preferably contains, at a minimum, the following information:
Time and Date of Decryption
Identification No. of Information Packet (IP)
Volume No. of CD-ROM
Information Owner or Distributor of IP
Type of IP (Classification)
Price Paid for IP
Billing Reference, if inserted by the User
When an item (IP) is purchased by a user, and the decryption controller is
able to complete this transaction by decrementing the financial account
and decrypting the item, this transaction is logged into the flash memory
38 of the controller. In this case, the logging operation is flagged
(Block 57) and carried out (Block 58) at the completion of the
transaction. Thereafter, the decryption controller returns to the idle
mode (Block 59).
Referring to FIG. 5, the retrieval of an item (IP) commences with a request
by the host computer 10 (Block 60). The host computer sends this request
to the decryption controller 14 via the SCSI bus which processes the
request and then sends the item to the host (Block 61), as if it were the
CD-ROM reader. The host computer 10 thus addresses the decryption
controller, rather than the CD-ROM reader; however, with the exception of
this difference, the host computer operates in such a manner as if it were
requesting the item of data directly from the CD-ROM reader. Thus, as far
as the host computer 10 is concerned, the decryption controller is the
CD-ROM reader; i.e., it is indistinguishable from, and "transparent" to
the host computer.
The decryption controller initially queries the file directory of the
CD-ROM to determine whether the item of information is encrypted (Block
62). If not, the decryption controller initiates a data request from the
CD-ROM reader 12 (Block 63) in the same manner as if it were the host
computer and reads the item into its own RAM memory. Thereafter, the data
item is transferred to the host computer (Block 61).
If the file directory indicates that the desired item is encrypted, the
decryption controller checks the user's financial account to determine if
there is a sufficient positive balance to pay for the item (Block 64). If
not, the decryption controller informs the host computer of the
insufficient credit (Block 65).
If credit is sufficient, the decryption controller transmits the cost of
the item to the host computer and asks the host to confirm the purchase
(Block 66) by displaying the cost to the user and requesting a user
response. If the user fails to accept the purchase, the transaction is
terminated (Block 67).
If the host computer confirms the purchase of the item at the price
indicated, the decryption controller initiates a data request to the
CD-ROM reader. The item is thus caused to be read by the CD-ROM reader and
it is transferred to the RAM of the decryption controller. Thereafter, the
item is decrypted using the DES module and the decryption keys (Block 68).
The purchase price of the item is then debited from the user's financial
account (Block 69) and the decrypted item is transferred to the host
computer (Block 61). Once the item of information has been supplied to the
host computer in decrypted form, it is available for storage, both
temporary and archival storage, and may be read and copied by the user, as
desired.
FIG. 6 illustrates the detailed operation of the decryption controller of
FIG. 2 in decrypting an item of information. As such, FIG. 6 represents
the operation of Block 68 in FIG. 5.
As an initial step, the controller obtains the entire item of information
(in encrypted form) from the CD-ROM (Block 70). Thereafter, the controller
determines the decryption key (Block 71) for this item from key rules and
key data which are available (e.g., stored) locally. Preferably, each
separate item of information has a unique decryption key. The method of
determining the key will be described in detail hereinafter in connection
with FIG. 7.
Since the DES module 42 of the decryption controller processes (decrypts)
only eight bytes of data at a time, a first group of eight bytes for the
information item to be decrypted is initially transferred to the DES
circuit (Block 72) and decrypted (Block 73). The result of this
decryption--that is, the cleartext--is placed temporarily in RAM (Block
74) and the process is repeated (Block 75) until all bytes of data of the
information item are decrypted. Thereafter, the entire information item in
cleartext is transmitted to the host computer (Block 61).
FIG. 7 illustrates how the decryption key is determined from the key rules
and the key data which are available locally for each separate item of
information stored on the CD-ROM. In order to determine the key, it is
necessary to obtain both the key rules and the key data for the specific
item of information, and then to apply the rules to this data. Examples of
both rules and data are given below.
The key rules and the key data are preferably obtained from one or more of
the following five sources:
(1) Non-volatile storage of a "system message" within the decryption
controller (flash memory);
(2) A "communication message" received from either the host computer, via
the SCSI bus or RS232C interface, or the central billing facility via the
telephone modem;
(3) A "media message" contained on the CD-ROM header which is generic to
all the files stored thereon (for example, the volume number of the
CD-ROM);
(4) A "file message" constructed from information on the file directory
associated with the specific item of information (IP) to be decrypted (for
example, the identity, length, location and date of the respective file)
and/or the header portion of the IP itself; and
(5) A "current status message" obtained from some element of the decryption
controller (for example, the real time clock) or the host computer.
Referring to FIG. 7, it is seen that a "key message"--that is, the key
rules and key data for generating a key--is obtained by retrieving a
stored system message (Block 80), by retrieving a stored communication
message (Block 81), by reading the media message from the CD-ROM (Block
82), by reading the file directory and header of the selected IP from the
CD-ROM (Block 83), and by obtaining the current status of the decryption
controller (Block 84). With this information, all of which is available
locally at the user site, the key rules and key data are selected (Block
85). Thereafter, the key data is applied to the key rules (Block 86) to
produce the decryption key.
By way of example and not limitation, the following key rules are
suggested:
(1) Add the CD-ROM volume number from the media message to the length of
the IP from the file message.
(2) Add the date from the media message to the date from the file message.
(3) Add the most recent communication message (initial vector) to the file
location in the file message.
(4) Subtract the date found in the file message (date of creation of the
IP) from the current status (present date). If the result is positive and
less than one year, proceed to decrypt. If the result is negative or more
than one year, do not generate a key (do not decrypt).
Other combinations of key rules and key data will readily occur to those
skilled in the art.
There has thus been shown and described a novel system for retrieving
secure information from a mass storage medium which fulfills all the
objects and advantages sought therefor. Many changes, modifications,
variations and other uses and applications of the subject invention will,
however, become apparent to those skilled in the art after considering
this specification and the accompanying drawings which disclose the
preferred embodiments thereof. All such changes, modifications, variations
and other uses and applications which do not depart from the spirit and
scope of the invention are deemed to be covered by the invention, which is
to be limited only by the claims which follow.
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