United States Patent
`US 6,993,134 B1
`(10) Patent No.:
`(12)
`Epstein
`(45) Date of Patent:
`Jan. 31, 2006
`
`
`US006993134B1
`
`(54) KEY EXCHANGE VIA A PORTABLE
`REMOTE CONTROL DEVICE
`
`wha)
`
`(75)
`
`.
`
`2
`
`Inventor: us A. Epstein, Spring Valley, NY
`
`.
`
`.
`
`(73) Assignee: Koninklijke Philips Electronics N.V.,
`Eindhoven (NL)
`Subjectto any eisclaimer, the ermoF this
`ec “154(b)by Odays. under 3
`(21) Appl. No.: 09/370,488
`22)
`Filed:
`Aug. 9, 1999
`(22)
`File
`"8."
`(51)
`Int. Cl.
`(2006.01)
`HO4L 9/00
`380/262: 713/171; 705/66:
`(52) US. Cl
`a 380/283:380/285: 455/410: 455352: 45588:
`,
`3484 0s
`,
`,
`(58) Field of Classification Search
`455188
`.
`455/352, 410; 348/14.05; 380/900, sane5
`See application file for complete search histor
`PP
`P
`y:
`References Cited
`U.S. PATENT DOCUMENTS
`
`(*) Notice:
`
`(56)
`
`Pees:
`
`;
`
`5,028,919 A *
`7/1991 Hidaka oo... 340/825.72
`
`5,371,794 A * 12/1994 Diffie etal. oo. 380/21
`5,886,753 A *
`3/1999 Shinyagaito ........ ee 348/734
`
`OTHER PUBLICATIONS
`
`Bruce Schneier: Applied Cryptography 2"? Edition, Oct.
`1995, John Wiley & Sons Pub., pp. 518-520.*
`:
`:
`* cited by examiner
`Primary Examiner—Emmanuel L. Moise
`Assistant Examiner—Paul E. Callahan
`57
`67)
`
`ABSTRACT
`
`The communications meansthat are commonly provided for
`the remote control of electronic components are utilized to
`effect an exchange of parameters to facilitate a crypto-
`graphic key exchange. The bidirectional remote control
`transceivers, typically infrared transceivers, that are com-
`monly used to communicate commands from the remote
`control device and to communicate feedback to the remote
`control device are configured to communicate parameters
`between a pair of consumerdevices that are controllable by
`the remote control device. In a preferred embodimentofthis
`invention the remote control device contains the control
`meansto effect the transfer of these parameters between the
`consumer devices.
`
`4,905,279 A *
`
`2/1990 Nishio ...... cece 455/352
`
`8 Claims, 4 Drawing Sheets
`
`
`
`SET-TOP BOX
`310
`
`RC XCEIVER
`320
`
`
`
`
`
`DVD PLAYER
`330
`
`
`
`TELEVISION
`
`DISPLAY DEVICE
`300
`
`RC XCEIVER
`220
`
`RC XCEIVER
`320
`
`RC XCEIVER
`
`
`
`
`
`320
`
`
`RC XCEIVER
`320
`
`REMOTE
`CONTROL
`390
`
`
`
`
`
`
`Roku EX1027
`U.S. Patent No. 7,589,642
`
`Roku EX1027
`U.S. Patent No. 7,589,642
`
`

`

`U.S. Patent
`
`Jan. 31, 2006
`
`Sheet 1 of 4
`
`US 6,993,134 B1
`
` TRANSMIT
`
`
`
` GENERATE RANDOM
`
`
`RECEIVE
`g,
`
`
`GENERATE RANDOM
`NUMBER y
`
`
`
`
`
`K'=XY mod
`==(gXY mod n
`
`
`
`
`110
`
`120
`
`130
`
`gn
`
`NUMBER x
`
`
`
`
`
` K=¥*modn
`= (VX mod n
`
`
`161
`
` CONTENT
`MATERIAL
`
`
`
` M
`
`BCR
`
`EM
`
`SP
`
`pecaverey) usng ke
`
`L~t9s
`
`150
`
`io]
`
`150
`
`M
`
` CONTENT
`MATERIAL
`
`u
`
`
`
`FIG. 1
`PRIOR ART
`
`

`

`U.S. Patent
`
`Jan. 31, 2006
`
`Sheet 2 of 4
`
`US 6,993,134 B1
`
`FIG. 2
`PRIOR ART
`
`OVD PLAYER
`330
`
`RC XCEIVER
`320
`
`
`
`TELEVISION
`DISPLAY DEVICE
`330
`
`RC XCEIVER
`320
`
`VCR
`360
`
`RC XCEIVER
`
`
`
`320
`
`
`
`
`
`SET-TOP BOX
`310
`
`RC XCEIVER
`320
`
`RC XCEIVER
`320
`
`REMOTE
`CONTROL
`300
`
`FIG. 3
`
`

`

`U.S. Patent
`
`Jan. 31, 2006
`
`Sheet 3 of 4
`
`US 6,993,134 B1
`
`41]
`
`APPLIANCE
`FUNCTIONS
`410
`
`KEY
`PARAMETER
`
`BENET
`
`KEY
`PARAMETER
`GENERATOR
`540
`
`| 3208|3208 |
`
`XMITR
`
`
`
`
`
`
`
`RCVR
`
`XY
`
`CONTROLLER
`393
`
`DISPLAY||DISPLAY
`399
`398
`
`REMOTE CONTROL
`DEVICE
`390
`
`FIG. 4
`
`

`

`U.S. Patent
`
`Jan. 31, 2006
`
`Sheet 4 of 4
`
`US 6,993,134 B1
`
`atA
`
`REMOTE DEVICE
`
`91
`
`913
`vr
`ALERT A
`ALERT B
`PREPARE FOR
`KEV EXCHANGE|44
`
`
`pees
`a
`
`GENERATE RANDOM
`NUMBERY
`I,
`
`
`
` COMPUTE Y
`
`
`COMPUTE X
`
`
`
`
`
`
`
`
`
`942
`
`972
`
`932|=o%modn
`
`
`
`
`COMPUTE KEY
`COMPUTE KEY
`982 = modn|gaa
`= ¥Xmodn
`
`
`
`
`
`
`
`FIG. 5
`
`

`

`US 6,993,134 B1
`
`1
`KEY EXCHANGE VIA A PORTABLE
`REMOTE CONTROL DEVICE
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`This invention relates to the field of consumerelectronics,
`and in particular to encryption techniques for copy and
`display protection for copyright material.
`2. Description of Related Art
`Digital recordings have the unique property that copies of
`the recorded material have the same quality as the original.
`As such,the need for an effective copy protection schemeis
`particularly crucial for the protection of copyright material
`that is digitally recorded. A number of protection schemes
`have been developed or proposedthat rely upon a secure link
`between electronic devices. These schemes typically rely
`upon the manufacturers of the electronic devices to comply
`with an agreed upon standard to make the mass production
`of protected material economically infeasible. For example,
`a set top box may communicate a received broadcast to a
`receiving device, such as a VCR or
`television,
`in an
`encrypted form that is only decryptable by the intended
`receiving device. In like manner, a playback device, such as
`a VCR or DVD, communicates the material in an encrypted
`form that
`is only decryptable by its intended receiving
`device, and so on.
`To effect this one-to-one encryption scheme,the proposed
`standards often call for the establishment of the encrypted
`link via a mutual key exchange. One such key exchange
`system is the “Diffie-Hellman” key-exchange algorithm,
`common in the art. FIG. 1 illustrates an example flow
`diagram for a key-exchange and subsequent encryption of
`content material using the Diffie-Hellman scheme. At 110, a
`first device, Device A, transmits a large prime n, and a
`number g that is primitive mod n, as a message 111 to a
`second device, Device B, that receives n and g, at 115. Each
`device, at 120 and 125, generate a large random number, x
`and y, respectively. At 130, Device A computes a number X
`that is equal to g* mod n; and, at 135, Device B computes a
`numberY that is equal to g” mod n. Device A communicates
`X to Device B, and Device B communicates Y to Device A,
`via messages 131, 136, respectively. Note that the determi-
`nation of x from a knowledge of g and X, and y from a
`knowledge of g and Y, is computationally infeasible, and
`thus, an eavesdropper to the exchangeof g, n, X, and Y will
`not be able to determine x or y. Device A computes a key K
`that is equal to Y* mod n, at 140, and Device B computes a
`key K' that is equal to X” mod n, at 145. Note that both K
`and K' are equal to g” mod n, and thus Device B knows
`Device A’s key, and vice versa, while an eavesdropperto the
`exchange of g, n, X, and Y will not know the key, because
`the eavesdropper does not know x or y. This exchange of
`information from which to generate the knowledge of a
`corresponding key is termed a key exchange.
`After effecting the key exchange, Device A encrypts the
`content material M 150 and communicates the encrypted
`material E,(M) to Device B, at 160, via communications
`path 161. Because Device B’s key K'is identical to the key
`K that is used to encrypt the content material M 150, Device
`B uses key K' to decrypt the received encrypted material
`E,(M)to create a decrypted copy 150!of the content material
`M 150, at 165. An eavesdropper to the communications path
`161, not having a knowledge of the key K, is unable to
`decrypt the encrypted material E,(M), and thus unable to
`create a copy of the content material M 150.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`Note that the above described key exchange, and virtually
`all known secure key exchanges, require a bidirectional
`transfer of information between the devices. Many con-
`sumer electronic devices, however, are configured for a
`unidirectional transfer of content material. For example, as
`illustrated in FIG. 2, a conventional set-top box 210 or DVD
`player 230 includes a wide-bandwidth transmitter for trans-
`mitting 211, 212, 231, 232 the content material to a VCR 260
`or display device 250, but rarely includes a receiver for
`receiving communications from the VCRor display device.
`In a device such as the VCR 260 that has bidirectional
`
`communications capabilities 251, 261, the key exchange can
`be effected by multiplexing the key exchange messages111,
`131, 136 of FIG. 1 onto the same paths 251, 261 that are
`used to communicate content material. Note, however, that
`the adoption of this multiplexing scheme for key exchange
`requires that
`the receiving device 250 contain receiving
`equipmentthat is compatible with the transmission 261 of
`content material. Thus, a conventional DVD player 230 that
`transmits 232 wide-bandwidth content material to the VCR
`
`260 will be required to also contain a wide-bandwidth
`receiver
`to receive wide-bandwidth content-compatible
`transmissions 262 from the VCR to effect a key exchange,
`even though the DVD player will have no otherpractical use
`for this wide-bandwidth communications path 262. Note,
`also, that a switching means will be required at the VCR to
`redirect the wide-bandwidth output, from the conventional
`connection 261 to a display device 250, to the DVD player
`via this newly required communications path 262. Alterna-
`tively, additional transmitters, receivers, and communica-
`tions connectors can be added to each consumer component
`210, 220, 250, 260, etc. to effect the key exchange. Each of
`these options requires additional material and manufacturing
`costs to add the required communications and connection
`equipment.
`
`BRIEF SUMMARY OF THE INVENTION
`
`It is an object of this invention to provide a method and
`system for effecting a cryptographic key exchange between
`consumerelectronic components that utilizes communica-
`tions devices and paths that are common to most consumer
`electronic components. It is a further object of this invention
`to provide an inexpensive system for effecting a crypto-
`graphic key exchange between consumerelectronic compo-
`nents. It is a further object of this invention to provide a
`method and system for effecting a cryptographic key
`exchange between consumer electronic components that is
`substantially independent of the physical location of the
`components.
`These objects and others are effected by utilizing the
`communications means that are commonly provided for the
`remote control of electronic components to effect a key
`exchange. As more sophisticated capabilities are provided
`for the remote control of equipment, most state of the art
`consumerelectronic devices are being configured with bidi-
`rectional
`infrared transceivers for
`receiving commands
`from, and providing feedback to, the remote control device.
`In accordance with this invention, these bidirectional remote
`control
`transceivers are configured to communicate the
`parameters
`required to effect
`the
`cryptographic key
`exchange between consumer devices. The principles pre-
`sented in this invention may also be used to transfer other
`parameters and information among consumer electronic
`devices.
`In a preferred embodiment of this invention a
`
`

`

`US 6,993,134 B1
`
`3
`remote control device contains the control means to effect
`the transfer of these parameters between the consumer
`devices.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The invention is explained in further detail, and by way of
`example, with reference to the accompanying drawings
`wherein:
`
`FIG. 1 illustrates an example flow diagram ofa priorart
`cryptographic key exchange technique.
`FIG. 2 illustrates an example block diagram of a prior art
`system of consumerelectronic devices.
`FIG. 3 illustrates an example block diagram of a system
`of consumer electronic devices with bidirectional remote
`control capabilities in accordance with this invention.
`FIG. 4 illustrates an example block diagram of a pair of
`consumerelectronic devices and a remote control device in
`accordance with this invention.
`
`FIG. 5 illustrates an example flow diagram of a key
`exchange via a remote control device in accordancewith this
`invention.
`Throughout the drawings, same reference numerals indi-
`cate similar or corresponding features or functions.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`With the increasing use of convenience features for home
`automation and integrated audio-visual systems, the tradi-
`tional function of a remote control device has expanded to
`include feedback from the device being controlled. Copend-
`ing U.S. patent application “REMOTE CONTROL PRO-
`GRAM SELECTION BY GENRE”, U‘S. Ser. No. 09/282,
`319, filed Mar. 31, 1999 for Karen Travato, Dan Pelletier,
`Paul Rankin, and Jacquelyn Martino, for example, presents
`a remote control device that receives program information
`from the television, DVDorset-top box for display on the
`remote control device to facilitate a user selection among
`available programs, or to present information about a pro-
`gram currently being viewed, and is incorporated by refer-
`ence herein. Most state of the art consumer electronic
`
`devices contain bidirectional communications means, typi-
`cally an infrared transceiver, for communicating with a
`remote control device. The conventional “universal” remote
`control device includes such a bidirectional transceiver that
`can be configured to receive infrared codes from sole-
`appliance remote control devices to “learn” how to control
`each appliance.
`FIG. 3 illustrates a collection of consumer electronic
`devices that are controllable by a remote control device 390.
`Each consumerdevice, the set-top box 310, the DVD player
`330, the display device 350, and the VCR 360, contains a
`conventional remote control transceiver 320 for receiving
`commands from, and providing feedback to a corresponding
`conventional remote control transceiver 320 in the remote
`control device 390. In accordance with this invention, the
`remote control transceiver 320 in each deviceis also used to
`
`effect a cryptographic key exchange by communicating
`parameters to each other. Note that although this invention
`is presented in the context of transferrmg key-exchange
`parameters, any other parameters or information items may
`also be communicated among devices via the remote control
`transceivers 320 in the light of this disclosure.
`The communication of parameters between consumer
`electronic devices 310, 330, 350, and 360 can be effected via
`a direct communication between each pair of devices, but in
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`the remote control device 390
`a preferred embodiment,
`effects a relay, or store-and-forward function,to facilitate the
`parameter exchange. Typically, remote control transceivers
`320 use line-of-sight communications means, such as infra-
`red transmissions. Often, consumer electronic devices are
`placed in close proximity to each other, with each remote
`control
`transceiver 320 oriented in the same direction,
`toward the expected location of a user of the remote control
`device 390. As such, adjacent devices are not within the line
`of sight of each other’s remote control
`transceiver 320.
`Because each of the adjacent devices are, by intent, within
`the line of sight of the remote control device 390, the remote
`control device 390 is well suited to be a relay between the
`adjacent devices. Also, when the consumer devices are not
`adjacent to each other, they are often located in physically
`separate areas. For example, a home may be configured to
`allow a television in a bedroom to receive content material
`
`from a VCRthatis located in a family room. By configuring
`the remote control device 390 as a store and forward relay
`system, the remote control device 390 can be configured to
`receive a parameter from a device in one room,then transmit
`the parameter to another device whenit is brought into the
`proximity of the other device. It can then receive a parameter
`from the other device, and transmit it to the original device
`when it is brought into the proximity of original device.
`Copending U.S. patent application, “REMOTE CONTROL
`DEVICE WITH LOCATION DEPENDENT INTER-
`FACE”, U.S. Ser. No. 09/210,416, filed Dec. 11, 1998 for
`Joost Kemink and Yevgeniy Shteyn, presents a remote
`control device whose operation is dependent upon the physi-
`cal location of the device, and is incorporated by reference
`herein. Note that the parameter exchange for a key exchange
`need only occur once between the devices; thereafter, the
`encrypted content material
`is communicated between
`devices in separate rooms via the aforementioned conven-
`tional wide-bandwidth channels, using, for example, coaxial
`cable between the rooms.
`FIG. 4 illustrates an example block diagram of a pair of
`consumerelectronic devices 400, 500 and a remote control
`device 390 in accordance with this invention. Each of the
`devices 400, 500, and 390 includes a remote control trans-
`ceiver 320 that is illustrated as a transmitter 320A and a
`
`receiver 320B. The devices 400, 500 may be any pair of
`consumer devices that have a need to transfer parameters,
`such as the devices 310, 330, 350, 360 of FIG. 3. As noted
`above, an exchange of parameters via the consumer devices
`400 and 500 may be effected in accordance with this
`invention via direct communication paths 401, 501, but
`often such paths maynotbe physically practical to establish.
`In a preferred embodiment of this invention,
`the remote
`control device 390 facilitates the parameter transfer via a
`store-and-forward relay technique. The operation of the
`devices 400, 500, 390 to effect the parametertransferis best
`explained with reference to the example flow diagram of
`FIG. 5. In the foregoing description,
`transmissions from
`each device 400, 500, and 390 are via the transmitter 390A
`within each device 400, 500, and 390, and receptions at each
`device 400, 500, and 390 are via the receiver 390B within
`each device 400, 500, and 390. The respective controllers
`430, 530, and 393 of the devices 400, 500, 390, effect the
`example flow of FIG. 5, respectively.
`At 910 of FIG. 5, the controller 393 of the remote control
`device 390 transmits an alert message 911, 913 to each
`device 400, 500, respectively, to establish the network of
`communications among the devices 400, 500, 390. Methods
`for communication among different devices are common in
`the art and traditionally used for commonly available “uni-
`
`

`

`US 6,993,134 B1
`
`5
`versal” remote controllers. In a preferred embodiment, the
`establishment of the network at 910 maybe initiated via an
`entry on the keypad 398, or via the receipt of a request (not
`shown) from, for example, device A, signaling that it has
`content material to communicate to device B, and requesting
`that the remote device 390 facilitate the parameter transfer
`required to effect a key exchange between device A and
`device B.
`Uponreceipt of the alert 911, 913 the controllers 430, 520
`of each device 400, 500 prepare for the key exchange, at
`912, 914, respectively. Illustrated in the example of FIG. 5
`is a key exchange based on the Diffie-Hellman key exchange
`technique. The application of the principles of this invention
`to other key exchange techniques, or other parameter
`exchange applications, will be evident to one of ordinary
`skill in the art in light of the principles presented herein.
`Each device 400, 500 generates a large random numberx, y
`via their respective key parameter generators (440, 540 in
`FIG. 4). Techniques for generating or selecting random
`numbers, or pseudo-random numbers, are common in the
`art. To effect the Diffie-Hellman key exchange, the remote
`control device 390 transmits, at 930, a large prime n, and a
`numberg that is primitive mod n, to each device 400, 500,
`via messages 931, 933, respectively. At 932, 934, each
`device computes the parameter X, Y that is to be transferred,
`based on the “secret” random numbersx, y, respectively. In
`the example Diffie-Hellman key exchange, X is equal to g*
`mod n, and Y is equal to gy mod n.
`Based upon an agreed upon convention, or protocol, one
`of the devices transmits its parameter first. In a preferred
`embodiment, the device having content material to send,
`device A 400 in the illustrated example, transmits its param-
`eter X 941 to the remote device 390, at 942. As would be
`evidentto one of ordinary skill in the art, any one of a variety
`of protocols may be employed to effect this transmission.
`For example, the remote device 390 may send a promptto
`each device wheneverit is ready to receive the parameter, or
`the device 400, 500 may repeatedly send the parameter until
`the remote device 390 sends an acknowledgment that it
`received the parameter, and so on. Because the encryption
`and subsequent decryption of the content material is depen-
`dent upon an accurate communication of the parameters X,
`Y, error checking and error correction techniques, common
`in the art, are employed in a preferred embodiment. The
`parameter X 941 is received from the device A 400, at 940,
`and subsequently transmitted to device B 500, at 950.
`Device B receives the parameter X 941, at 954, and trans-
`mits its parameter Y 963 to the remote control device 390,
`at 964. The remote control device 390 receives the param-
`eter Y 963, at 960, and, within the locale of device A 400,
`transmits the parameter Y 963 to device A 400. Each device
`400, 500 subsequently computes a key that is equal to g”
`mod n byraising the received parameter Y, X to the power
`of the “secret” random numberx, y, at 982, 984, respec-
`tively.
`the
`If the devices are in physically separate locales,
`remote control device 390 transmits the alert 911, and
`parameters g, n 931 to device A 400 and receives the
`parameter X 941, at 940, andis then transported to the locale
`of device B 500. At the locale of device B 500, the control
`device 390 transmits the alert 913, the parameters g, n 933,
`and the parameter X 941, at 950.
`Returning to FIG. 4, having exchanged parameters X, Y,
`the key parameter generators 440, 540 provide the deter-
`mined key K, K’', each equal to g” mod n,to their corre-
`sponding encryptor 420 and decryptor 520 devices, respec-
`tively. Each of the devices 400, 500, is illustrated as having
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6
`an appliance function block 410, 510, respectively. These
`blocks 410, 510 represent the convention functions provided
`by each device, such as the receipt of content material by a
`set-top box, the recording and playback functions of a VCR,
`the display and tuning functions of a television, and so on.
`Note that, in conventional use, the appliance functions 410,
`510 are controllable by the remote control device 390, and
`feedback from the appliance functions 410, 510, or the
`controllers 430, 530, are provided to the remote control
`device 390, via the transmitters 320A and receivers 320B of
`each device 400, 500, 390. Feedback messages are display-
`able on the display 395 of the remote control device 390, and
`may include messages and promptsthat are applicable to the
`above described parameter exchange processorotherrelated
`tasks.
`When the device A 400 has content material M 411 to
`communicate securely to device B 500, the material M 411
`is encrypted by the encryptor 420 to provide an encrypted
`material E,(M) 421. The encrypted material E,(M) 421 is
`subsequently communicated to device B 500, via a wide-
`bandwidth communications channel 405. The decryptor 520
`decrypts the received encrypted material E,(M)' 421'
`to
`produce a copy of the content material M' 411’
`that
`is
`processable by the appliance function 510, for example, to
`render a display of the content material M' 411' correspond-
`ing to the original material M 411.
`The foregoing merely illustrates the principles of the
`invention.It will thus be appreciated that those skilled in the
`art will be able to devise various arrangements which,
`although not explicitly described or shown herein, embody
`the principles of the invention and are thus within its spirit
`and scope. For example, the control flows illustrated in FIG.
`5 may be effected automatically, or via a sequence of
`operations communicated via the keypad 398 of the remote
`control device 390 in FIG. 4. The particular configurations
`and sequences of the figures are presented for illustration
`purposes. The functions illustrated may be effected, for
`example, in alternative devices. For example, the parameters
`g and n may be provided by one of the devices 400, 500,
`rather than the remote device 390. In other systems, com-
`mon in the art, one or more of the parameters may be
`embedded in the devices 400, 500, obviating the need for
`random numbergenerators. If the parameters X and Y are
`embedded in the device, certificates verifying the authen-
`ticity of these parameters may also be supplied. In like
`manner,either of the devices 400, 500 may be configured to
`control the parameter exchange, and the remote control may
`be configured as a relatively “unintelligent” relay device.
`For example, the messages from the transmitters 320A may
`include conventional communications packets having a des-
`tination address, and the remote device 390 may be config-
`ured to merely receive the packet and retransmit it to the
`device associated with the destination address. These and
`other system configuration and optimization features will be
`evident to one of ordinary skill in the art in view ofthis
`disclosure, and are included within the scope of the follow-
`ing claims.
`I claim:
`
`1. Aremote control device that is configured to facilitate
`control of a plurality of electronic devices, comprising:
`an input device that is configured to accept a user input
`and provides therefrom a control signal for control of a
`first device of the plurality of electronic devices;
`a receiver that is configured to receive a parameter from
`a second device of the plurality of electronic devices;
`a transmitter that is configured to:
`
`

`

`US 6,993,134 B1
`
`7
`communicate the parameter from the second device to
`the first device;
`communicate the control signal to the first device to effect
`the control of an appliance function ofthe first device;
`and
`
`a controller that effects the communication of the param-
`eter and the other parameter,
`wherein
`the receiver is further configured to receive an other
`parameter from the first device, and
`the transmitter is further configured to communicate the
`other parameter from the first device to the second
`device, and
`wherein the controller effects the communication of the
`
`parameter and the other parameter to establish a cryp-
`tographic key exchange.
`2. The remote control device of claim 1, wherein the
`cryptographic key exchange corresponds to a Diffie-Hell-
`man key exchange.
`3. An electronic device comprising:
`a transceiver that is structured to receive control com-
`mands from a remote control device,
`an appliance apparatus that effects a processing of input
`information in dependence upon the control com-
`mands,
`a parameter generator that produces a parameter for
`communication to an other device, and wherein,
`the transceiveris also structured to transmit the parameter,
`thereby effecting the communication of the parameter
`to the other device, wherein
`the transceiver is also structured to receive an other
`
`parameter that is communicated from the other device
`and wherein
`
`the parameter generator also produces
`a cryptographic key based on the other parameter that is
`communicated from the other device.
`
`4. The electronic device of claim 3, wherein the parameter
`generator produces the parameter and the cryptographic key
`in accordance with a Diffie-Hellman key exchange tech-
`nique.
`5. A method for effecting a parameter exchange between
`a first device and a second device, the first device and the
`second device each having a transceiver that communicates
`with a remote control device to facilitate control ofthe first
`device and the second device via the remote control device,
`the method comprising:
`
`8
`transmitting a first parameter from the first device via a
`transmitter of the transceiver of the first device;
`receiving the first parameter at the second device via a
`receiver of the transceiver of the second device;
`receiving the first parameter at the remote control device;
`transmitting the first parameter to the second device from
`the remote control device;
`transmitting a second parameter from the second device
`via a transmitter of the transceiver of the second device;
`receiving the second parameter at the first device via a
`receiver of the transceiver of the first device; and
`receiving the second parameter at
`the remote control
`device; and
`transmitting the second parameterto thefirst device from
`the remote control device.
`6. A method for effecting a parameter exchange between
`a first device and a second device, the first device and the
`second device each having a transceiver that communicates
`with a remote control device to facilitate control of the first
`device and the second device via the remote control device,
`the method comprising:
`transmitting a first parameter from the first device via a
`transmitter of the transceiver of the first device;
`receiving the first parameter at the second device via a
`receiver of the transceiver of the second device;
`receiving the first parameter at the remote control device;
`transmitting the first parameter to the second device from
`the remote control device;
`transmitting a second parameter from the second device
`via a transmitter of the transceiver of the second device;
`receiving the second parameter at the first device via a
`receiver of the transceiver of the first device;
`generating a first cryptographic key at the first device
`based on the second parameter; and
`generating a second cryptographic key at
`device based on the first parameter,
`wherein the second cryptographic key is suitable for a
`decryption of material that is encrypted using the first
`cryptographic key.
`7. The method of claim 6, wherein thefirst cryptographic
`key and the second cryptographic key are equal.
`8. The method of claim 6, wherein the generating of the
`first and the second cryptographic keys is based on a
`Diffie-Hellman key-exchange technique.
`*
`*
`*
`*
`*
`
`the second
`
`10
`
`15
`
`25
`
`30
`
`45
`
`