United States Patent [19J
`Jia et al.
`
`I lllll llllllll Ill lllll lllll lllll lllll lllll 111111111111111111111111111111111
`US005991402A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,991,402
`Nov. 23, 1999
`
`[54] METHOD AND SYSTEM OF DYNAMIC
`TRANSFORMATION OF ENCRYPTED
`MATERIAL
`
`Primary Examiner-Tod R. Swann
`Assistant Examiner-Paul E. Callahan
`Attorney, Agent, or Firm-Pennie & Edmonds LLP
`
`[75]
`
`Inventors: Zheng Jia, Germantown; Ji Shen,
`Gaithersburg, both of Md.
`
`[73] Assignee: AegiSoft Corporation, Rockville, Md.
`
`[21] Appl. No.: 08/935,955
`
`[22] Filed:
`
`Sep. 23, 1997
`
`Int. Cl.6
`....................................................... H04K 1/02
`[51]
`[52] U.S. Cl. .......................... 380/9; 380/9; 380/3; 380/4;
`380/23; 380/25; 705/59; 713/164; 713/165;
`713/166; 713/190
`[58] Field of Search ................................. 380/3, 4, 23, 25
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,151,938
`5,388,211
`5,410,598
`5,537,143
`5,708,709
`5,717,756
`5,758,069
`5,764,762
`5,790,663
`5,805,706
`5,825,883
`5,826,011
`
`9/1992 Griffin, III et al. ....................... 380/43
`2/1995 Hornbuckle ............................. 395/200
`4/1995 Shear .......................................... 380/4
`7/1996 Steingold et al.
`........................ 348/13
`1/1998 Rose ............................................ 380/4
`2/1998 Coleman ................................... 380/25
`5/1998 Olsen ................................. 395/187.01
`6/1998 Kazmierczak et al. ..................... 380/4
`8/1998 Lee et al. .................................... 380/4
`9/1998 Davis ........................................ 380/49
`10/1998 Archibald et al. ........................ 380/25
`10/1998 Chou et al. ............................. 395/186
`
`[57]
`
`ABSTRACT
`
`The present invention provides a method and system that
`enables software-on-demand and software subscription ser(cid:173)
`vices based on a dynamic transformation filter technology.
`The invention is also useful in the distribution of other
`electronic material. The apparatus utilized in this invention
`does not create any intermediate storage of decrypted mate(cid:173)
`rial that is under the protection of this technology. Instead,
`the apparatus is implemented as a virtually integral part of
`the operating system that monitors and "filters" all read,
`write, and open/execute access to and from the 1/0 devices,
`such as a hard drive. As the protected material is being
`accessed for read, write or open/execute, the transformation
`filter positions itself in the critical path which is required for
`loading the material through the low level file system layer
`to the high level application layer. The material enters the
`transformation filter in its encrypted state. The transforma(cid:173)
`tion filter decrypts the material in real-time as it goes
`through, and hands over the material in its original state to
`the upper level operating system component to fulfill the
`access requests. Because the need for intermediate storage is
`eliminated, the decrypted material in its original state is only
`visible to integral parts of the operating system components
`and not to other system users. As a result, security is
`significantly improved over prior art systems.
`
`20 Claims, 4 Drawing Sheets
`
`101
`
`Local
`Application
`
`102
`
`Local
`Application
`
`103
`
`Network
`Application
`
`107
`
`Transformation Filter
`
`108
`
`105
`
`File System Drivers
`
`Network File System Drivers
`
`106
`
`1/0 Devices
`
`IPR2017-00184
`UNIFIED EX1011
`
`

`
`U.S. Patent
`
`Nov. 23, 1999
`
`Sheet 1 of 4
`
`5,991,402
`
`101
`
`102
`
`Local
`Application
`
`Local
`Application
`
`103
`
`Network
`Application
`
`107
`
`108
`
`OS File System Manager
`
`Network Service Provider
`
`Transformation Filter
`
`105
`
`File System Drivers
`
`Network File System Drivers
`
`106
`
`1/0 Devices
`
`FIG. 1
`
`

`
`U.S. Patent
`
`Nov. 23, 1999
`
`Sheet 2 of 4
`
`5,991,402
`
`201
`
`203
`
`202
`
`PE
`
`fE
`
`205
`
`206
`
`207
`
`208
`
`A
`(LICENSE
`MANAGER)
`
`c
`(CLIENT APP)
`
`F
`(TRANSFORMATION
`FILTER)
`
`D
`(PRODUCT
`DATA)
`
`210
`
`209
`
`210
`
`FIG. 2
`
`

`
`U.S. Patent
`
`Nov. 23, 1999
`
`Sheet 3 of 4
`
`5,991,402
`
`307
`
`Dp
`(PROFILE DATA)
`
`Pu
`{UNIQUE ID GENERATION)
`
`UNIQUE ID
`
`D
`{PRODUCT DATA)
`
`301
`
`M1
`(PRE-INSTALL
`MATERIAL)
`
`312
`
`308
`
`302
`
`P1
`(USER INSTALLATION PROCESS)
`
`314
`
`313
`
`306
`
`309
`
`PEs
`(UNIQUE KEY GENERATION+ 2ND
`ENCRYPTION)
`310
`
`311
`
`ME
`(UNIQUELY
`ENCRYPTED MATERIAL)
`
`DL
`(LICENSE+
`USAGE DATE)
`
`303
`
`304
`
`306
`
`A
`(LICENSE
`MANAGER)
`
`C
`(CLIENT APP)
`
`F
`(TRANSFORMATION
`FILTER)
`
`FIG. 3
`
`

`
`U.S. Patent
`
`Nov. 23, 1999
`
`Sheet 4 of 4
`
`5,991,402
`
`SYSTEM 1/0 REQUESTS
`MONITOR 1/0 REQUESTS 416
`
`REQUESTS TO OPEN/EXECUTE/READ FILE
`GET FILE + LICENSE INFO 403
`
`No
`
`402
`
`TRANSFORMATION FILTER
`
`414
`
`No
`
`LAUNCH CLIENT 1 - - (cid:173)
`APPLICATION
`
`SECURITY MONITOR 408
`
`KEY GENERATION
`
`409
`
`DECRYPTING
`TRANSFORMATION
`
`41 0
`
`415
`
`Yes
`
`LAUNCH LICENSE
`MANAGER
`
`HAND-OVER
`
`413
`
`FIG. 4
`
`

`
`5,991,402
`
`1
`METHOD AND SYSTEM OF DYNAMIC
`TRANSFORMATION OF ENCRYPTED
`MATERIAL
`BACKGROUND OF THE INVENTION
`1. The Technical Field
`This invention relates to metered usage of computer
`software and other intellectual property existing in elec(cid:173)
`tronic digital format. The end result of the invention enables
`services such as software-on-demand and software subscrip- 10
`tion. This invention can also be applied to the prevention of
`piracy of computer software and other intellectual property.
`2. Description of the Prior Art
`In the current consumer market, computer software and
`other intellectual property existing in digital format are
`primarily marketed the same as other hard goods commodi(cid:173)
`ties. However, while video tapes and other hard goods are
`rented routinely, software products typically are still avail(cid:173)
`able only on a purchase basis. As a result, at least two useful
`services generally are not available: software-on-demand
`and software subscription. Software-on-demand is a service
`that would allow consumers to pay for software products on
`a per-use basis. Software subscription is a service that would
`make one or more software products available to consumers
`on a periodic subscription basis such as once a month.
`Despite the obvious benefits of these services, the inher(cid:173)
`ent nature of software products has posed significant tech(cid:173)
`nical challenges to enabling technology providers. In order
`to successfully support these services, the enabling technol(cid:173)
`ogy should meet the following criteria:
`I. Security. Software product made available in software(cid:173)
`on-demand and subscription format should be protected
`and regulated in a totally secure manner. The enabling
`technology must defend the software from the most
`skilled and determined hackers. In particular, at no time
`should the software in its original state be present on an
`intermediate storage medium, because this simply opens
`the door for skilled system level hackers. There is also the
`possibility that utilities would become available that
`would make such an intermediate storage medium acces(cid:173)
`sible to the public.
`II. Non-Intrusiveness. The enabling technology should not
`require modification of source code in order to protect and
`meter usage. In contrast, intrusive technology embeds
`itself in the source code of software products and requires 45
`recompilation of the software. This effort introduces sig(cid:173)
`nificant overhead in the protection process in terms of
`extra coding and testing resources, and is highly error
`prone.
`III. Minimal System Overhead. The enabling technology 50
`should not impose significant overhead while protecting,
`launching, and metering usage of the software product.
`Typical overhead introduced by enabling technology
`includes the need for extra RAM and hard disk storage
`space, the launching of the protecting process before 55
`decrypting protected software, and competition for other
`system resources, such as the CPU, while monitoring
`usage.
`IV. Immunity From System Clock Reset. By altering a
`computer system's clock setting, users of software prod- 60
`ucts can significantly prolong their allowed usage period
`and consequently compromise the effectiveness of
`software-on-demand and software subscription services.
`The enabling technology should be able to detect and take
`counter-measure actions against system clock resets.
`V. Perpetual Protection And Metering. Once a software
`publisher puts his software under the protection and
`
`2
`control of the enabling technology, it should be perpetu(cid:173)
`ally protected and controlled. Subsequent copies and
`reinstallation should not disable the protection and con(cid:173)
`trol.
`VI. User Friendliness. The enabling technology should not
`alter a computer user's environment in a way that causes
`changes in system settings that are noticeable to the user.
`The user interface should be totally intuitive and easy to
`use.
`Available prior art protection techniques are based on
`"wrapper" and "redirection" technologies. A "wrapper"
`often takes the form of a operating system shell program or
`an altered start-up code section of the protected software. Its
`function is to shield direct access to the protected software.
`15 When the protected software is accessed by users, the
`"wrapper" will be executed first. The protected software in
`its encrypted state will be then decrypted and restored on a
`temporary storage medium in its original state. The "wrap(cid:173)
`per" will then redirect the access to the restored software on
`20 the temporary storage medium.
`A system developed by TestDrive Corporation in Santa
`Clara, Calif., offers try-before-buy software evaluation ser(cid:173)
`vices. This system converts an original version of software
`to a disabled version that may be used for a limited trial or
`25 evaluation period. If purchase of software is desired, an
`unlock code may be purchased that converts the software to
`its original state. In a preferred embodiment, this prior art
`system is applied to chosen material, such as a computer
`program, and a portion of the material is separated from the
`30 original material. In this way, a denatured version of the
`original material that includes the separated portion of the
`material and the residual portion of the material is produced.
`During the trial period, the denatured version of the material
`is placed into a temporary storage medium but only the
`35 separated portion is readily accessed by a system user.
`Alternatively, the separated portion of the material may be
`replaced with a modified portion, for example, a counter
`may be included to limit the number of times the material
`may be accessed, or interfering material may be added to the
`40 original material, such as beeps in an audio signal, or a mask
`in a visual signal.
`Several drawbacks in these "wrapper" and "redirection"
`technology based systems are obvious.
`I. Security flaw. Since "wrapper" and "redirection" technol(cid:173)
`ogy requires a temporary storage medium to physically
`host either all the restored software or the residual portion
`of the software in its original state, the very existence of
`the material in its original state accessible by a system
`user makes the system vulnerable to hacker attacks. It is
`possible for an operating system expert to gain access to
`the material in its original state and redistribute a pirated
`version of the material. A utility software program could
`also possibly be developed to perform this act of piracy
`repeatedly and can be made available in the public
`domain to further damage the effectiveness of the enabled
`services. While wrapper and redirection technologies can
`protect software from novice attacks, they are not highly
`secure against experts.
`II. System overhead. Launching the "wrapper" program,
`physically storing the restored software in its original
`state, and creating and administrating the temporary stor(cid:173)
`age medium all impose delay before launching the user
`desired software product. These activities also compete
`for other system resources with other processes run by the
`operating system.
`III. Space overhead. Storage of the restored software product
`in its original state in Random Access Memory (RAM)
`
`65
`
`

`
`5,991,402
`
`10
`
`4
`the usage of software products and other intellectual prop(cid:173)
`erty existing in digital format. Such material can be ordered
`on-demand multiple times and can also be available on a
`subscription basis. Copying of the installed material to other
`computers will only produce an encrypted version of the
`material. However, a permanent copy of the decrypted
`material can be generated at the discretion of its publisher.
`The invention provides components of the system that
`allows users of such material to connect via a modern or
`existing private network, and Internet connection to a clear(cid:173)
`ing house server. The clearing house server will in turn
`generate an authorization code for enabling metered usage
`of the material upon receiving an order and a charge card
`number. Currently acceptable charge cards include regular
`credit cards and debit cards. Future payment methods will
`illustratively include smart cards and digital cash. These
`components of the system will also be able to process
`customer returns and exchanges.
`The present invention is able to operate with material
`20 distributed via all possible channels, such as electronic
`material distribution over the Internet, CD-ROMs distrib(cid:173)
`uted at physical store fronts, DVDs, VCDs, cable modem,
`and other broadcasting channels.
`The present invention also operates in an network envi-
`ronment where access to material over a network file system
`is equally regulated and metered by the system.
`
`25
`
`3
`will require greater than 100% more RAM space than the
`protected software normally requires. In a multiple pro(cid:173)
`cess operating system, where multiple protected software
`can be executed simultaneously, this overhead require(cid:173)
`ment can be multiplied and significantly impact the sys(cid:173)
`tem's performance.
`IV. Unwelcome Nuisance. The creation of a temporary
`storage medium in a computer system, such as a virtual
`device, is an artifact normally unwelcome and foreign to
`computer system users. Therefore, the user will eventu-
`ally want to purchase the original material in its entirety
`to eliminate the nuisance and artifacts generated by wrap(cid:173)
`per and redirection technologies. Thus, these technologies
`do not lend themselves to providing perpetual usage
`metering and protection services.
`Currently there is no known highly secure method that 15
`provides real time decryption of encrypted software or other
`electronic material without redirecting and storing the
`decrypted material on a temporary medium.
`SUMMARY OF THE INVENTION
`The present invention provides a method and system that
`enables software-on-demand and software subscription ser(cid:173)
`vices based on a dynamic transformation filter technology.
`The invention is also useful in the distribution of other
`electronic materials. The apparatus utilized in this invention
`does not create any intermediate storage of decrypted mate(cid:173)
`rial that is under the protection of this technology. Instead,
`the apparatus is implemented as a virtually integral part of
`the operating system that monitors and "filters" all read,
`write, and open/execute access to and from the 1/0 devices, 30
`such as a hard drive. As the protected material is being
`accessed for read, write or open/execute, the transformation
`filter positions itself in the critical path which is required for
`loading the material through the low level file system layer
`to the high level application layer. The material enters the 35
`transformation filter in its encrypted state. The transforma(cid:173)
`tion filter decrypts the material as it goes through, and hands
`over the material in its original state to the upper level
`operating system component to fulfill the access requests.
`Because the need for intermediate storage is eliminated, the 40
`decrypted material in its original state is only visible to
`integral parts of the operating system components and not to
`other system users. As a result, security is significantly
`improved over prior art systems.
`The transformation filter is formed by converting a pro- 45
`grammable service that is provided by the operating system
`for a totally different purpose into a "filtering" security and
`regulating system. Preferably, in the case of Windows 95™
`software, this programmable service is a virtual device
`driver; and in the case of Windows NT™ it is a kernel mode 50
`driver.
`The present invention can operate with material that is not
`intrusively embedded inside the protected material. It pro(cid:173)
`vides an utility that encrypts any material with a few easy to
`follow steps. The invention adopts standard data encryption
`mechanisms made available by the U.S. government and
`commercial companies. However, the apparatus in this
`invention provides enhanced key management capabilities
`to further ensure security of the encrypted material. All
`material installed on the consumer's PC goes through two
`encryption processes. The second encryption process
`requires a dynamically unique key generated from the
`computer user's unique ID. The dynamic generation of the
`key ensures that no unlocking key can be obtained directly
`from files stored on the hard disk.
`The present invention make it possible for the transfor(cid:173)
`mation filter to perpetually regulate, meter, and charge for
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`These and other objects, features and advantages of the
`invention will be more readily apparent from the following
`detailed description of the invention in which:
`FIG. 1 is a high level architecture diagram depicting
`components of the system, their relative positions and inter(cid:173)
`relationships and the direction of data flow;
`FIG. 2 depicts the process of encrypting and packaging of
`original material into a protected state;
`FIG. 3 depicts the process of installing the protected
`product onto a user's computer, including the generation of
`a unique ID and a second encryption with a user unique key;
`and
`FIG. 4 is a flowchart depicting the internal process flow
`of the transformation filter.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`The current invention is a method and apparatus that is
`integrated into the internals of an operating system, such as
`Microsoft Windows 95 or Window NT. This method and
`apparatus enables dynamic decryption of encrypted material
`in real time without redirection to a temporary storage
`medium. Consequently the invention allows software prod-
`ucts and other materials in electronic format to be protected
`through encryption and to be made available for regulated
`55 and metered usage.
`In the preferred embodiment of the present invention, a
`transformation filter is implemented as a kernel level pro(cid:173)
`gram operating in a multi-process operating system envi(cid:173)
`ronment; and the encrypted material is application software.
`60 However, the invention may also be applied to other con(cid:173)
`texts such as the distribution of audio or visual materials in
`encrypted form.
`FIG. 1 is a high level architecture diagram depicting the
`position and function of the transformation filter within the
`65 operating system.
`High level application programs, including local applica(cid:173)
`tions and network applications 101, 102, 103, request access
`
`

`
`5,991,402
`
`5
`to software materials residing on system 1/0 devices 106 to
`perform read, write, and open/execute activities. These
`requests must be submitted to the operating system compo(cid:173)
`nents like an OS file system manager 107 or a network
`service provider 108, and be relayed to a file system driver
`layer or a network file system driver layer 105 which is also
`on the kernel level. In accordance with the invention, a
`transformation filter 104 is positioned between the applica(cid:173)
`tions 101, 102, 103 and the file system driver layer 105.
`Illustratively, in the context of Windows 95™ Software, the 10
`transformation filter is implemented as a virtual device
`driver; and in the case of Windows NT™ it is implemented
`as a kernel mode driver.
`If access requests coming from local and/or network
`applications to file system drivers are considered to be going
`"downstream", then all data being read from 1/0 devices to
`upper layers of the operating system are considered to be
`going "upstream". Both downstream (from application
`down to file system) and upstream (from file system to
`application) data must go through a particular path which is 20
`referred to as the critical path in this document. Transfor(cid:173)
`mation filter 104 is in the critical path.
`Whenever data passes through the transformation filter in
`an upstream direction, the transformation filter performs the
`necessary transformation that converts the encrypted soft(cid:173)
`ware into its original state. The software that has been
`transferred to its original state is then handed over to upper
`layers of the operating system. If the request is from an
`application, e.g., an image viewer to open a file for display,
`the transformed software material will eventually be handed 30
`over to the application. From the requesting application's
`perspective, opening this encrypted software material is no
`different from opening any other original software material.
`The transformation process is totally transparent to the
`requesting application. If the request is to execute the file 35
`(e.g., double mouse clicking on the file) and the original
`software material is an executable program, the transformed
`software will be handed over to the operating system's
`loader to execute in memory. This process is considered
`"filtering" because encrypted software moving upstream 40
`goes into the apparatus and comes out in its decrypted state
`as if it went through a filtering device. No intermediate
`storage of the decrypted software is ever exposed to system
`users during the whole "filtering" process. All handing-over
`and decrypting processes take place inside the operating 45
`system as internal activities in a highly secure fashion.
`Transformation filter 104 is implemented as if it were an
`integral part of the operating system. Extra security mea(cid:173)
`sures are built into transformation filter 104 so that it not 50
`only is capable of "filtering" upstream and downstream data,
`but also monitors hacking activities within the operating
`system and takes countermeasures to prevent any security
`breaches from taking place.
`FIG. 2 is a block diagram depicting the process of
`encrypting the original software material into its pre(cid:173)
`installed encrypted stage. As shown in FIG. 2, original
`software material M0 201 is encrypted by application of a
`transformation function f E 202 in an encryption process PE
`203. The encryption process preferably is a standard encryp(cid:173)
`tion process such as DES or RSA The result of this
`encryption process is encrypted software ME 204, which
`may be transmitted securely over various distribution
`channels, such as CD-ROMs, the Internet, and others.
`During a second process Ps 209, four other components 65
`that support successful regulation and metering of the soft(cid:173)
`ware's usage are added to ME204. These components are a
`
`6
`license manager 205, a client application 206, a transforma(cid:173)
`tion filter 207, and a product specific signature data 208.
`License manager 205 is a software program that is respon(cid:173)
`sible for maintaining a license database including data on
`usage of the encrypted software, interfacing with users of the
`encrypted software material MD and terminating usage of
`the encrypted software material upon expiration of an autho(cid:173)
`rized usage period. Client application 206 is a software
`program that is used to request from a clearinghouse server
`authorization to use the encrypted software material MD and
`to receive from the clearinghouse server an appropriate
`authorization code. This activity may also involve some
`form of electronic payment, such as provision of a credit or
`debit card number. In addition, the client application may
`15 also include the capability of obtaining pricing, promotion
`and upgrade information and downloading additional soft(cid:173)
`ware. Transformation filter 207 is the software which con(cid:173)
`trols access to the encrypted software material ME. Further
`details of this software are described in conjunction with
`FIGS. 1 and 4. Product specific signature data 208 is a code
`unique to the particular encrypted software material ME.
`The output of process 209 is a single output file MI 210,
`which is the pre-installation encrypted software material and
`comprises all the input components 204, 205, 206, 207, 208.
`25 Process 209 preferably just combines components 204, 205,
`206, 207, 208 into a single software product. Alternatively,
`process 209 could also involve an additional encryption
`process.
`In the preferred embodiment of the invention, output file
`MI takes on the name, icon and other properties of the
`original software material. Therefore, from an external point
`of view, this file appears to be identical to the original
`software. This embodiment is primarily for the purpose of
`eliminating extra steps for software publishers in packaging
`their software products.
`Subsequently, software publishers can use their favorite
`installation packaging utility, such as InstallShield™, to put
`their software into a normal installation package as if the
`encryption processes of FIG. 2 had never taken place.
`FIG. 3 is a block diagram depicting the process of
`installing encrypted software material onto a user's PC. In a
`preferred embodiment, output file MI launches its own
`installation process 302 after a user goes through normal
`procedures for installing the software just as if the software
`had never been encrypted. Installation process PI 302
`spawns off the key components of the pre-installation soft(cid:173)
`ware material MI 210/301. First, a license manager 303, a
`client application 304 and a transformation filter 305 are
`extracted and installed in proper hidden places in the system.
`Product specific signature data 306 and the encrypted soft-
`ware ME are also obtained.
`Simultaneously, user profile data and operating system
`specific information, represented as DP 307 is transformed
`55 by a transformation function f 1 308 in process Pu 312 to
`generate a unique ID 313 for the customer. Any number of
`conventional techniques can be used in process 312 to
`generate unique ID 313. Advantageously, we prefer to use a
`time stamp with a precision measured in milliseconds in
`60 generating the unique ID because the probability that two
`users will install their software at the same millisecond is
`virtually zero. Unique ID 313 is subsequently used in all
`phases and components of the system.
`Product specific signature data 306, unique ID 313 and the
`encrypted software ME are supplied to a process PEs 309.
`Process PEs uses the inverse of the transformation function
`f E to decrypt the software material and thereby restore the
`
`

`
`5,991,402
`
`25
`
`30
`
`7
`original material M0 . Such decryption processes are well
`known. Then, it immediately re-encrypts M0 with a unique
`encryption key based on the unique ID 313 and the product
`specific signature data 306. Again, standard encryption
`processes such as DES or RSA may be used. The result is a
`uniquely encrypted software material Mu310. The software
`material Mu is then installed above driver layer 105 (See
`FIG. 1).
`In the preferred embodiment, the invention never stores
`the unique encryption key used for the generation of Mu.
`Whenever necessary, this unique key can be dynamically
`regenerated using the same inputs (the unique ID and the
`product specific signature data) and key generation process.
`This key management strategy makes it extremely difficult
`to compromise the encrypted software material. The unique(cid:173)
`ness of the key also assures that no identical encrypted
`software material exists on any two user's computers once
`the software is installed.
`At the end of installation, a license database DL 311 is
`generated that keeps all license information, a usage counter,
`and other important information to successfully implement
`a usage regulation and metering process described below in
`conjunction with FIG. 4. The license database identifies the
`encrypted software as being "registered", that is, being
`subject to the system of the present invention. The database
`is also stored in the computer system.
`Referring to FIG. 1, transformation filter 104 is installed
`in the computer system so that it intercepts all requests to
`access software files resident on 1/0 devices 106. In the
`Windows 95™ operating system this is accomplished by
`installing the transformation filter as a virtual device driver.
`In the Windows NT™ operating system this is accomplished
`by installing the transformation filter as a kernel mode
`driver.
`User activities such as read, write, execute the software or
`open software material for viewing are processed by the
`operating system. A higher level operating system process
`(e.g., a local or network application 101, 102, 103 of FIG. 1)
`is responsible for passing a request for such activities
`downstream to driver layer 105 through transformation filter
`104.
`FIG. 4 illustrates the detailed internal process flow of the
`transformation filter. As indicated by box 416, the transfor(cid:173)
`mation filter continuously monitors the operating system for
`all 1/0 requests. When such a request reaches the transfor(cid:173)
`mation filter, it initiates the get software+ license info pro(cid:173)
`cess 403. This process obtains the license information (if
`any) for the requested software including the latest status on
`the software's usage, license, authorization code, expiration
`date, product specific signature data 208/306, along with
`other pertinent information. Subsequently, two validation
`tests are applied: a test if the software is registered (step 406)
`and a test if the license is valid (step 407). If the requested
`software was not registered, the transformation filter simply 55
`transfers control back to the operating system's requesting
`process at step 413 without taking any further actions. If the
`software is registered, the transformation filter checks at step
`407 whether there is a valid license for it. In case there is no
`valid license, a client application is launched at step 414 to 60
`prompt the user to order more usage or purchase the soft-
`ware.
`The order entry process is handled by the client applica(cid:173)
`tion component of the system. The client application con(cid:173)
`nects the user's computer to a clearinghouse server via a 65
`modem or existing Internet connections. The clearinghouse
`server, upon receiving a valid credit card or debit card
`
`8
`number, in turn generates an authorization code to activate
`legitimate usage of the registered software.
`If a valid license for the software is present and the
`execution is within the authorized usage period, the trans(cid:173)
`formation filter starts a security monitor process 408 to
`perform a scan of any third party processes that might be
`attempting to hijack data going out of the transformation
`filter after being decrypted. In case that suspicious activity
`is present in the operating system, the transformation filter
`10 takes countermeasures to eliminate the potential threat.
`Next, the unique key to be used to decrypt the encrypted
`software is generated in key generation process 409. This
`key is generated from the unique ID 313 and the product
`specific signature data 306. Using the generated decryption
`15 key and the inverse of encryption process 309, the transfor(cid:173)
`mation filter then decrypts in real-time all the encrypted
`portion of the software in the decrypting transformation
`process 410. The decrypted software in its original state is
`then handed-over at step 413 to the requesting process. The
`20 operating system may now successfully process the execu(cid:173)
`tion or feed the decrypted software material to an application
`that requested access.
`Once the decrypted software is handed-over to the
`requesting process, the transformation filter starts a usage
`metering counter at step 411. While the usage counter runs,
`the transformation filter continually